Remove unused stages from shader programs

A stage is deemed unused if it has no main function after optimization,
or if a SPIR-V entry point's interface variables all become unused during
specialization.

diff --git a/source/core/module.cpp b/source/core/module.cpp
index 11d11af5d6485b1f7a80671f15dba95394554c21..f42a0da76a17d75f30c2da746fcf35f061a8e1ae 100644 (file)
--- a/source/core/module.cpp
+++ b/source/core/module.cpp
@@ -14,6 +14,7 @@ enum SpirVConstants
        OP_NAME = 5,
        OP_MEMBER_NAME = 6,
        OP_ENTRY_POINT = 15,
+       OP_EXECUTION_MODE = 16,
        OP_TYPE_VOID = 19,
        OP_TYPE_BOOL = 20,
        OP_TYPE_INT = 21,
@@ -269,6 +270,8 @@ SpirVModule *SpirVModule::specialize(const map<string, int> &spec_values) const
                }
        }
 
+       for(const EntryPoint &e: entry_points)
+               flags[e.id] = 0;
        for(const Variable &v: variables)
                flags[v.id] = 0;
        for(const InstructionBlock &b: blocks)
@@ -307,7 +310,8 @@ SpirVModule *SpirVModule::specialize(const map<string, int> &spec_values) const
                                unsigned start = new_code.size();
                                new_code.push_back(opcode);
                                new_code.push_back(*(op+1));
-                               new_code.push_back(*(op+2));
+                               unsigned func_id = *(op+2);
+                               new_code.push_back(func_id);
 
                                unsigned i=3;
                                while(i<word_count)
@@ -318,17 +322,29 @@ SpirVModule *SpirVModule::specialize(const map<string, int> &spec_values) const
                                                break;
                                }
 
+                               unsigned var_count = 0;
                                for(; i<word_count; ++i)
                                {
                                        unsigned id = *(op+i);
                                        if(flags[id])
+                                       {
+                                               ++var_count;
                                                new_code.push_back(id);
+                                       }
                                }
 
-                               new_code[start] |= (new_code.size()-start)<<16;
+                               if(var_count)
+                               {
+                                       flags[func_id] = 1;
+                                       new_code[start] |= (new_code.size()-start)<<16;
+                               }
+                               else
+                                       new_code.resize(start);
 
                                copy = false;
                        }
+                       else if(opcode==OP_EXECUTION_MODE)
+                               copy = flags[*(op+1)];
                        else if(opcode==OP_SPEC_CONSTANT_TRUE || opcode==OP_SPEC_CONSTANT_FALSE)
                        {
                                unsigned id = *(op+2);

diff --git a/source/glsl/compiler.cpp b/source/glsl/compiler.cpp
index 4c8c1d03d893d277395b2f64b5def34aa7e55168..05bf421cd422428dbf1b09b5eef3d0daf737c3f9 100644 (file)
--- a/source/glsl/compiler.cpp
+++ b/source/glsl/compiler.cpp
@@ -107,6 +107,19 @@ void Compiler::compile(Mode mode)
                        ++i;
        }
 
+       Stage *prev_stage = 0;
+       for(auto i=module->stages.begin(); i!=module->stages.end(); )
+       {
+               if(i->functions.empty())
+                       i = module->stages.erase(i);
+               else
+               {
+                       i->previous = prev_stage;
+                       prev_stage = &*i;
+                       ++i;
+               }
+       }
+
        for(Stage &s: module->stages)
        {
                StructuralFeatureConverter().apply(s, features);