[llvm] [SPIR-V] Implement SPV_KHR_float_controls2 (PR #146941)

[Marcos Maronas via llvm-commits]

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@@ -606,6 +664,73 @@ void SPIRVAsmPrinter::outputAnnotations(const Module &M) {
   }
 }
 
+void SPIRVAsmPrinter::outputFPFastMathDefaultInfo() {
+  // Collect the SPIRVTypes that are OpTypeFloat.
+  std::vector<const MachineInstr *> SPIRVFloatTypes;
+  for (const MachineInstr *MI : MAI->getMSInstrs(SPIRV::MB_TypeConstVars)) {
+    // Skip if the instruction is not OpTypeFloat.
+    if (MI->getOpcode() != SPIRV::OpTypeFloat)
+      continue;
+
+    // Collect the SPIRV type.
+    SPIRVFloatTypes.push_back(MI);
+  }
+
+  for (const auto &[Func, FPFastMathDefaultInfoVec] :
+       MAI->FPFastMathDefaultInfoMap) {
+    if (FPFastMathDefaultInfoVec.empty())
+      continue;
+
+    for (const MachineInstr *MI : SPIRVFloatTypes) {
+      unsigned OpTypeFloatSize = MI->getOperand(1).getImm();
+      unsigned Index = computeFPFastMathDefaultInfoVecIndex(OpTypeFloatSize);
+      assert(Index < FPFastMathDefaultInfoVec.size() &&
+             "Index out of bounds for FPFastMathDefaultInfoVec");
+      const auto &FPFastMathDefaultInfo = FPFastMathDefaultInfoVec[Index];
+      assert(FPFastMathDefaultInfo.Ty &&
+             "Expected target type for FPFastMathDefaultInfo");
+      assert(FPFastMathDefaultInfo.Ty->getScalarSizeInBits() ==
+                 OpTypeFloatSize &&
+             "Mismatched float type size");
+      MCInst Inst;
+      Inst.setOpcode(SPIRV::OpExecutionMode);
+      MCRegister FuncReg = MAI->getFuncReg(Func);
+      assert(FuncReg.isValid());
+      Inst.addOperand(MCOperand::createReg(FuncReg));
+      Inst.addOperand(
+          MCOperand::createImm(SPIRV::ExecutionMode::FPFastMathDefault));
+      MCRegister TypeReg =
+          MAI->getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
+      Inst.addOperand(MCOperand::createReg(TypeReg));
+      unsigned Flags = FPFastMathDefaultInfo.FastMathFlags;
+      if (FPFastMathDefaultInfo.ContractionOff &&
+          (Flags & SPIRV::FPFastMathMode::AllowContract) &&
+          FPFastMathDefaultInfo.FPFastMathDefault)
----------------
maarquitos14 wrote:

You're right, it's illegal. However, because `ContractionOff` --and `SignedZeroInfNanPreserve`--, is deprecated when `SPV_KHR_float_controls2` is enabled, and the spec suggests to use `FPFastMathDefault` instead, what we're doing is simply replacing the former with the latter. It is explained in https://github.com/llvm/llvm-project/blob/848611acb1917b292c890990c7ca44b172aec8be/llvm/lib/Target/SPIRV/SPIRVModuleAnalysis.h#L137C1-L145. Does that make sense?

https://github.com/llvm/llvm-project/pull/146941