Remapper: handle embedded opcode in OpSpecConstantOp

SPIRV/SPVRemapper.cpp

@@ -464,8 +464,8 @@ namespace spv {
     {
         const auto     instructionStart = word;
         const unsigned wordCount = asWordCount(instructionStart);
-        const spv::Op  opCode    = asOpCode(instructionStart);
         const int      nextInst  = word++ + wordCount;
+        spv::Op  opCode    = asOpCode(instructionStart);
 
         if (nextInst > int(spv.size()))
             error("spir instruction terminated too early");
@@ -506,6 +506,18 @@ namespace spv {
 
         // Store IDs from instruction in our map
         for (int op = 0; numOperands > 0; ++op, --numOperands) {
+            // SpecConstantOp is special: it includes the operands of another opcode which is
+            // given as a literal in the 3rd word.  We will switch over to pretending that the
+            // opcode being processed is the literal opcode value of the SpecConstantOp.  See the
+            // SPIRV spec for details.  This way we will handle IDs and literals as appropriate for
+            // the embedded op.
+            if (opCode == spv::OpSpecConstantOp) {
+                if (op == 0) {
+                    opCode = asOpCode(word++);  // this is the opcode embedded in the SpecConstantOp.
+                    --numOperands;
+                }
+            }
+
             switch (spv::InstructionDesc[opCode].operands.getClass(op)) {
             case spv::OperandId:
             case spv::OperandScope:

Test/baseResults/remap.specconst.comp.out

+remap.specconst.comp
+Warning, version 450 is not yet complete; most version-specific features are present, but some are missing.
+
+// Module Version 10000
+// Generated by (magic number): 80001
+// Id's are bound by 16104
+
+                              Capability Shader
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint GLCompute 5663  "main"
+                              ExecutionMode 5663 LocalSize 1 1 1
+                              Decorate 2 SpecId 0
+                              Decorate 3 SpecId 1
+                              Decorate 4 SpecId 2
+                              Decorate 5 BuiltIn WorkgroupSize
+               8:             TypeVoid
+            1282:             TypeFunction 8
+              11:             TypeInt 32 0
+               2:     11(int) SpecConstant 1
+               3:     11(int) SpecConstant 1
+               4:     11(int) SpecConstant 1
+              20:             TypeVector 11(int) 3
+               5:   20(ivec3) SpecConstantComposite 2 3 4
+               6:     11(int) SpecConstantOp 81 5 0
+               7:     11(int) SpecConstantOp 81 5 1(GLSL.std.450)
+               9:     11(int) SpecConstantOp 81 5 2
+              10:     11(int) SpecConstantOp 132 7 9
+              12:     11(int) SpecConstantOp 128 6 10
+            5663:           8 Function None 1282
+           16103:             Label
+                              Return
+                              FunctionEnd

gtests/Remap.FromFile.cpp

@@ -89,6 +89,7 @@ INSTANTIATE_TEST_CASE_P(
             { "remap.basic.everything.frag",              "main", Source::GLSL, spv::spirvbin_t::DO_EVERYTHING },
             { "remap.basic.dcefunc.frag",                 "main", Source::GLSL, spv::spirvbin_t::DCE_FUNCS },
             { "remap.basic.strip.frag",                   "main", Source::GLSL, spv::spirvbin_t::STRIP },
+            { "remap.specconst.comp",                     "main", Source::GLSL, spv::spirvbin_t::DO_EVERYTHING },
             { "remap.switch.none.frag",                   "main", Source::GLSL, spv::spirvbin_t::NONE },
             { "remap.switch.everything.frag",             "main", Source::GLSL, spv::spirvbin_t::DO_EVERYTHING },
             { "remap.literal64.none.spv",                 "main", Source::GLSL, spv::spirvbin_t::NONE },