updates templates for decoder in seperate class, adds again generated templates

CMakeLists.txt

@@ -20,6 +20,7 @@ set(LIB_SOURCES
     src/iss/arch/tgc5c.cpp
     src/vm/interp/vm_tgc5c.cpp
     src/vm/fp_functions.cpp
+    src/vm/instruction_decoder.cpp
     src/iss/semihosting/semihosting.cpp
 )
 

gen_input/templates/asmjit/CORENAME.cpp.gtl

@@ -37,6 +37,7 @@
 #include <iss/asmjit/vm_base.h>
 #include <asmjit/asmjit.h>
 #include <util/logging.h>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -79,22 +80,16 @@ public:
     }
 
 protected:
-    using super::mov;
-    using super::cmp;
     using super::get_ptr_for;
-    using super::get_reg;
-    using super::get_reg_Gp;
     using super::get_reg_for;
     using super::get_reg_for_Gp;
     using super::load_reg_from_mem;
     using super::load_reg_from_mem_Gp;
     using super::write_reg_to_mem;
-    using super::gen_ext;
     using super::gen_read_mem;
     using super::gen_write_mem;
     using super::gen_wait;
     using super::gen_leave;
-    using super::gen_operation;
     using super::gen_sync;
     using super::gen_set_tval;
    
@@ -121,27 +116,21 @@ private:
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, ${instructions.size()}> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */<%instructions.each{instr -> %>
         /* instruction ${instr.instruction.name}, encoding '${instr.encoding}' */
         {${instr.length}, ${instr.encoding}, ${instr.mask}, &this_class::__${generator.functionName(instr.name)}},<%}%>
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */<%instructions.eachWithIndex{instr, idx -> %>
     /* instruction ${idx}: ${instr.name} */
     continuation_e __${generator.functionName(instr.name)}(virt_addr_t& pc, code_word_t instr, jit_holder& jh){
@@ -206,72 +195,22 @@ private:
         gen_instr_epilogue(jh);
         return BRANCH;
     }
-     
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr: instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 continuation_e vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt, jit_holder& jh) {
@@ -287,7 +226,10 @@ continuation_e vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned
     if (instr == 0x0000006f || (instr&0xffff)==0xa001)
         throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) 
         f = &this_class::illegal_instruction;
     return (this->*f)(pc, instr, jh);

gen_input/templates/llvm/CORENAME.cpp.gtl

@@ -36,6 +36,7 @@
 #include <iss/iss.h>
 #include <iss/llvm/vm_base.h>
 #include <util/logging.h>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -136,27 +137,21 @@ private:
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, ${instructions.size()}> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */<%instructions.each{instr -> %>
         /* instruction ${instr.instruction.name}, encoding '${instr.encoding}' */
         {${instr.length}, ${instr.encoding}, ${instr.mask}, &this_class::__${generator.functionName(instr.name)}},<%}%>
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */<%instructions.eachWithIndex{instr, idx -> %>
     /* instruction ${idx}: ${instr.name} */
     std::tuple<continuation_e, BasicBlock*> __${generator.functionName(instr.name)}(virt_addr_t& pc, code_word_t instr, BasicBlock* bb){
@@ -219,58 +214,6 @@ private:
         this->builder.CreateBr(bb);
         return std::make_tuple(BRANCH, nullptr);
     }    
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename CODE_WORD> void debug_fn(CODE_WORD instr) {
@@ -282,13 +225,16 @@ template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr:instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 std::tuple<continuation_e, BasicBlock *>
@@ -309,13 +255,16 @@ vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt,
 //            res = this->core.read(this->core.v2p(pc + 2), 2, data + 2);
 //        }
 //    } else {
-        auto res = this->core.read(paddr, 4, data);
+    auto res = this->core.read(paddr, 4, data);
-        if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
+    if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
 //    }
     if (instr == 0x0000006f || (instr&0xffff)==0xa001) throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     // curr pc on stack
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) {
         f = &this_class::illegal_instruction;
     }

gen_input/templates/tcc/CORENAME.cpp.gtl

@@ -37,6 +37,7 @@
 #include <iss/tcc/vm_base.h>
 #include <util/logging.h>
 #include <sstream>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -130,34 +131,28 @@ protected:
         auto mask = (1ULL<<W) - 1;
         auto sign_mask = 1ULL<<(W-1);
         return (from & mask) | ((from & sign_mask) ? ~mask : 0);
-    }    
+    }
 
 private:
     /****************************************************************************
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, ${instructions.size()}> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */<%instructions.each{instr -> %>
         /* instruction ${instr.instruction.name}, encoding '${instr.encoding}' */
         {${instr.length}, ${instr.encoding}, ${instr.mask}, &this_class::__${generator.functionName(instr.name)}},<%}%>
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */<%instructions.eachWithIndex{instr, idx -> %>
     /* instruction ${idx}: ${instr.name} */
     compile_ret_t __${generator.functionName(instr.name)}(virt_addr_t& pc, code_word_t instr, tu_builder& tu){
@@ -198,59 +193,6 @@ private:
         vm_impl::gen_trap_check(tu);
         return BRANCH;
     }
-    
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename CODE_WORD> void debug_fn(CODE_WORD instr) {
@@ -262,13 +204,16 @@ template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr:instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 std::tuple<continuation_e>
@@ -287,13 +232,16 @@ vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt,
 //            res = this->core.read(this->core.v2p(pc + 2), 2, data + 2);
 //        }
 //    } else {
-        auto res = this->core.read(paddr, 4, reinterpret_cast<uint8_t*>(&instr));
+    auto res = this->core.read(paddr, 4, reinterpret_cast<uint8_t*>(&instr));
-        if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
+    if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
 //    }
     if (instr == 0x0000006f || (instr&0xffff)==0xa001) throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     // curr pc on stack
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) {
         f = &this_class::illegal_instruction;
     }

src/vm/asmjit/vm_tgc5c.cpp

@@ -37,6 +37,7 @@
 #include <iss/asmjit/vm_base.h>
 #include <asmjit/asmjit.h>
 #include <util/logging.h>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -79,22 +80,16 @@ public:
     }
 
 protected:
-    using super::mov;
-    using super::cmp;
     using super::get_ptr_for;
-    using super::get_reg;
-    using super::get_reg_Gp;
     using super::get_reg_for;
     using super::get_reg_for_Gp;
     using super::load_reg_from_mem;
     using super::load_reg_from_mem_Gp;
     using super::write_reg_to_mem;
-    using super::gen_ext;
     using super::gen_read_mem;
     using super::gen_write_mem;
     using super::gen_wait;
     using super::gen_leave;
-    using super::gen_operation;
     using super::gen_sync;
     using super::gen_set_tval;
    
@@ -121,20 +116,11 @@ private:
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, 87> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */
@@ -313,7 +299,10 @@ private:
         /* instruction DII, encoding '0b0000000000000000' */
         {16, 0b0000000000000000, 0b1111111111111111, &this_class::__dii},
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */
     /* instruction 0: LUI */
     continuation_e __lui(virt_addr_t& pc, code_word_t instr, jit_holder& jh){
@@ -4746,72 +4735,22 @@ private:
         gen_instr_epilogue(jh);
         return BRANCH;
     }
-     
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr: instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 continuation_e vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt, jit_holder& jh) {
@@ -4827,7 +4766,10 @@ continuation_e vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned
     if (instr == 0x0000006f || (instr&0xffff)==0xa001)
         throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) 
         f = &this_class::illegal_instruction;
     return (this->*f)(pc, instr, jh);

src/vm/instruction_decoder.cpp

@@ -0,0 +1,103 @@
+/*******************************************************************************
+ * Copyright (C) 2024 MINRES Technologies GmbH
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Contributors:
+ *       alex@minres.com - initial implementation
+ ******************************************************************************/
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <numeric>
+#include <vector>
+#include <vm/instruction_decoder.h>
+
+decoder::decoder(std::vector<generic_instruction_descriptor> instr_list) {
+    for(auto instr : instr_list) {
+        root.instrs.push_back(instr);
+    }
+    populate_decoding_tree(root);
+}
+
+void decoder::populate_decoding_tree(decoding_tree_node& parent) {
+    // create submask
+    parent.submask =
+        std::accumulate(parent.instrs.begin(), parent.instrs.end(), std::numeric_limits<uint32_t>::max(),
+                        [](int current_submask, const generic_instruction_descriptor& instr) { return current_submask & instr.mask; });
+    //  put each instr according to submask&encoding into children
+    for(auto instr : parent.instrs) {
+        bool foundMatch = false;
+        for(auto& child : parent.children) {
+            // use value as identifying trait
+            if(child.value == (instr.value & parent.submask)) {
+                child.instrs.push_back(instr);
+                foundMatch = true;
+            }
+        }
+        if(!foundMatch) {
+            decoding_tree_node child = decoding_tree_node(instr.value & parent.submask);
+            child.instrs.push_back(instr);
+            parent.children.push_back(child);
+        }
+    }
+    parent.instrs.clear();
+    // call populate_decoding_tree for all children
+    if(parent.children.size() > 1)
+        for(auto& child : parent.children) {
+            populate_decoding_tree(child);
+        }
+    else {
+        // sort instrs by value of the mask, so we have the least restrictive mask last
+        std::sort(parent.children[0].instrs.begin(), parent.children[0].instrs.end(),
+                  [](const generic_instruction_descriptor& instr1, const generic_instruction_descriptor& instr2) {
+                      return instr1.mask > instr2.mask;
+                  });
+    }
+}
+uint32_t decoder::decode_instr(uint32_t word) { return _decode_instr(this->root, word); }
+uint32_t decoder::_decode_instr(decoding_tree_node const& node, uint32_t word) {
+    if(!node.children.size()) {
+        if(node.instrs.size() == 1)
+            return node.instrs[0].index;
+        for(auto instr : node.instrs) {
+            if((instr.mask & word) == instr.value)
+                return instr.index;
+        }
+    } else {
+        for(auto child : node.children) {
+            if(child.value == (node.submask & word)) {
+                return _decode_instr(child, word);
+            }
+        }
+    }
+    return std::numeric_limits<uint32_t>::max();
+}

src/vm/instruction_decoder.h

@@ -0,0 +1,63 @@
+/*******************************************************************************
+ * Copyright (C) 2024 MINRES Technologies GmbH
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Contributors:
+ *       alex@minres.com - initial implementation
+ ******************************************************************************/
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <vector>
+
+struct generic_instruction_descriptor {
+    uint32_t value;
+    uint32_t mask;
+    uint32_t index;
+};
+
+struct decoding_tree_node {
+    std::vector<generic_instruction_descriptor> instrs;
+    std::vector<decoding_tree_node> children;
+    uint32_t submask = std::numeric_limits<uint32_t>::max();
+    uint32_t value;
+    decoding_tree_node(uint32_t value)
+    : value(value) {}
+};
+class decoder {
+public:
+    decoder(std::vector<generic_instruction_descriptor> instr_list);
+    uint32_t decode_instr(uint32_t word);
+
+private:
+    decoding_tree_node root{decoding_tree_node(std::numeric_limits<uint32_t>::max())};
+    void populate_decoding_tree(decoding_tree_node& root);
+    uint32_t _decode_instr(decoding_tree_node const& node, uint32_t word);
+};

src/vm/interp/vm_tgc5c.cpp

@@ -31,6 +31,7 @@
  *******************************************************************************/
 
 // clang-format off
+#include <cstdint>
 #include <iss/arch/tgc5c.h>
 #include <iss/debugger/gdb_session.h>
 #include <iss/debugger/server.h>
@@ -43,6 +44,7 @@
 #include <exception>
 #include <vector>
 #include <sstream>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -146,20 +148,11 @@ private:
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         typename arch::traits<ARCH>::opcode_e op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
     const std::array<instruction_descriptor, 87> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */
         {32, 0b00000000000000000000000000110111, 0b00000000000000000000000001111111, arch::traits<ARCH>::opcode_e::LUI},
@@ -250,6 +243,8 @@ private:
         {16, 0b1100000000000010, 0b1110000000000011, arch::traits<ARCH>::opcode_e::C__SWSP},
         {16, 0b0000000000000000, 0b1111111111111111, arch::traits<ARCH>::opcode_e::DII},
     }};
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
 
     iss::status fetch_ins(virt_addr_t pc, uint8_t * data){
         if(this->core.has_mmu()) {
@@ -270,58 +265,6 @@ private:
         }
         return iss::Ok;
     }
-    
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-
-    typename arch::traits<ARCH>::opcode_e  decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return arch::traits<ARCH>::opcode_e::MAX_OPCODE;
-    }
 };
 
 template <typename CODE_WORD> void debug_fn(CODE_WORD insn) {
@@ -347,13 +290,16 @@ constexpr size_t bit_count(uint32_t u) {
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr:instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 inline bool is_icount_limit_enabled(finish_cond_e cond){
     return (cond & finish_cond_e::ICOUNT_LIMIT) == finish_cond_e::ICOUNT_LIMIT;
@@ -390,9 +336,13 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
         } else {
             if (is_jump_to_self_enabled(cond) &&
                     (instr == 0x0000006f || (instr&0xffff)==0xa001)) throw simulation_stopped(0); // 'J 0' or 'C.J 0'
-            auto inst_id = decode_instr(root, instr);
+            uint32_t inst_index = instr_decoder.decode_instr(instr);
+            opcode_e inst_id = arch::traits<ARCH>::opcode_e::MAX_OPCODE;;
+            if(inst_index <instr_descr.size())
+                inst_id = instr_descr.at(instr_decoder.decode_instr(instr)).op;
+
             // pre execution stuff
-             this->core.reg.last_branch = 0;
+            this->core.reg.last_branch = 0;
             if(this->sync_exec && PRE_SYNC) this->do_sync(PRE_SYNC, static_cast<unsigned>(inst_id));
             try{
                 switch(inst_id){

src/vm/llvm/vm_tgc5c.cpp

@@ -36,6 +36,7 @@
 #include <iss/iss.h>
 #include <iss/llvm/vm_base.h>
 #include <util/logging.h>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -136,20 +137,11 @@ private:
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, 87> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */
@@ -328,7 +320,10 @@ private:
         /* instruction DII, encoding '0b0000000000000000' */
         {16, 0b0000000000000000, 0b1111111111111111, &this_class::__dii},
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */
     /* instruction 0: LUI */
     std::tuple<continuation_e, BasicBlock*> __lui(virt_addr_t& pc, code_word_t instr, BasicBlock* bb){
@@ -4885,58 +4880,6 @@ private:
         this->builder.CreateBr(bb);
         return std::make_tuple(BRANCH, nullptr);
     }    
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename CODE_WORD> void debug_fn(CODE_WORD instr) {
@@ -4948,13 +4891,16 @@ template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr:instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 std::tuple<continuation_e, BasicBlock *>
@@ -4975,13 +4921,16 @@ vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt,
 //            res = this->core.read(this->core.v2p(pc + 2), 2, data + 2);
 //        }
 //    } else {
-        auto res = this->core.read(paddr, 4, data);
+    auto res = this->core.read(paddr, 4, data);
-        if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
+    if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
 //    }
     if (instr == 0x0000006f || (instr&0xffff)==0xa001) throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     // curr pc on stack
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) {
         f = &this_class::illegal_instruction;
     }

src/vm/tcc/vm_tgc5c.cpp

@@ -37,6 +37,7 @@
 #include <iss/tcc/vm_base.h>
 #include <util/logging.h>
 #include <sstream>
+#include <vm/instruction_decoder.h>
 
 #ifndef FMT_HEADER_ONLY
 #define FMT_HEADER_ONLY
@@ -130,27 +131,18 @@ protected:
         auto mask = (1ULL<<W) - 1;
         auto sign_mask = 1ULL<<(W-1);
         return (from & mask) | ((from & sign_mask) ? ~mask : 0);
-    }    
+    }
 
 private:
     /****************************************************************************
      * start opcode definitions
      ****************************************************************************/
     struct instruction_descriptor {
-        size_t length;
+        uint32_t length;
         uint32_t value;
         uint32_t mask;
         compile_func op;
     };
-    struct decoding_tree_node{
-        std::vector<instruction_descriptor> instrs;
-        std::vector<decoding_tree_node*> children;
-        uint32_t submask = std::numeric_limits<uint32_t>::max();
-        uint32_t value;
-        decoding_tree_node(uint32_t value) : value(value){}
-    };
-
-    decoding_tree_node* root {nullptr};
 
     const std::array<instruction_descriptor, 87> instr_descr = {{
          /* entries are: size, valid value, valid mask, function ptr */
@@ -329,7 +321,10 @@ private:
         /* instruction DII, encoding '0b0000000000000000' */
         {16, 0b0000000000000000, 0b1111111111111111, &this_class::__dii},
     }};
- 
+
+    //needs to be declared after instr_descr
+    decoder instr_decoder;
+
     /* instruction definitions */
     /* instruction 0: LUI */
     compile_ret_t __lui(virt_addr_t& pc, code_word_t instr, tu_builder& tu){
@@ -3637,59 +3632,6 @@ private:
         vm_impl::gen_trap_check(tu);
         return BRANCH;
     }
-    
-    //decoding functionality
-
-    void populate_decoding_tree(decoding_tree_node* root){
-        //create submask
-        for(auto instr: root->instrs){
-            root->submask &= instr.mask;
-        }
-        //put each instr according to submask&encoding into children
-        for(auto instr: root->instrs){
-            bool foundMatch = false;
-            for(auto child: root->children){
-                //use value as identifying trait
-                if(child->value == (instr.value&root->submask)){
-                    child->instrs.push_back(instr);
-                    foundMatch = true;
-                }
-            }
-            if(!foundMatch){
-                decoding_tree_node* child = new decoding_tree_node(instr.value&root->submask);
-                child->instrs.push_back(instr);
-                root->children.push_back(child);
-            }
-        }
-        root->instrs.clear();
-        //call populate_decoding_tree for all children
-        if(root->children.size() >1)
-            for(auto child: root->children){
-                populate_decoding_tree(child);      
-            }
-        else{
-            //sort instrs by value of the mask, this works bc we want to have the least restrictive one last
-            std::sort(root->children[0]->instrs.begin(), root->children[0]->instrs.end(), [](const instruction_descriptor& instr1, const instruction_descriptor& instr2) {
-            return instr1.mask > instr2.mask;
-            }); 
-        }
-    }
-    compile_func decode_instr(decoding_tree_node* node, code_word_t word){
-        if(!node->children.size()){
-            if(node->instrs.size() == 1) return node->instrs[0].op;
-            for(auto instr : node->instrs){
-                if((instr.mask&word) == instr.value) return instr.op;
-            }
-        }
-        else{
-            for(auto child : node->children){
-                if (child->value == (node->submask&word)){
-                    return decode_instr(child, word);
-                }  
-            }  
-        }
-        return nullptr;
-    }
 };
 
 template <typename CODE_WORD> void debug_fn(CODE_WORD instr) {
@@ -3701,13 +3643,16 @@ template <typename ARCH> vm_impl<ARCH>::vm_impl() { this(new ARCH()); }
 
 template <typename ARCH>
 vm_impl<ARCH>::vm_impl(ARCH &core, unsigned core_id, unsigned cluster_id)
-: vm_base<ARCH>(core, core_id, cluster_id) {
+: vm_base<ARCH>(core, core_id, cluster_id)
-    root = new decoding_tree_node(std::numeric_limits<uint32_t>::max());
+, instr_decoder([this]() {
-    for(auto instr:instr_descr){
+        std::vector<generic_instruction_descriptor> g_instr_descr;
-        root->instrs.push_back(instr);
+        g_instr_descr.reserve(instr_descr.size());
-    }
+        for (uint32_t i = 0; i < instr_descr.size(); ++i) {
-    populate_decoding_tree(root);
+            generic_instruction_descriptor new_instr_descr {instr_descr[i].value, instr_descr[i].mask, i};
-}
+            g_instr_descr.push_back(new_instr_descr);
+        }
+        return std::move(g_instr_descr);
+    }()) {}
 
 template <typename ARCH>
 std::tuple<continuation_e>
@@ -3726,13 +3671,16 @@ vm_impl<ARCH>::gen_single_inst_behavior(virt_addr_t &pc, unsigned int &inst_cnt,
 //            res = this->core.read(this->core.v2p(pc + 2), 2, data + 2);
 //        }
 //    } else {
-        auto res = this->core.read(paddr, 4, reinterpret_cast<uint8_t*>(&instr));
+    auto res = this->core.read(paddr, 4, reinterpret_cast<uint8_t*>(&instr));
-        if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
+    if (res != iss::Ok) throw trap_access(TRAP_ID, pc.val);
 //    }
     if (instr == 0x0000006f || (instr&0xffff)==0xa001) throw simulation_stopped(0); // 'J 0' or 'C.J 0'
     // curr pc on stack
     ++inst_cnt;
-    auto f = decode_instr(root, instr);
+    uint32_t inst_index = instr_decoder.decode_instr(instr);
+    compile_func f = nullptr;
+    if(inst_index < instr_descr.size())
+        f = instr_descr[inst_index].op;
     if (f == nullptr) {
         f = &this_class::illegal_instruction;
     }