[Backport to 14] Add fast math flag translation for OpenCL std lib

lib/SPIRV/SPIRVReader.cpp

@@ -2460,8 +2460,11 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
   case OpExtInst: {
     auto *ExtInst = static_cast<SPIRVExtInst *>(BV);
     switch (ExtInst->getExtSetKind()) {
-    case SPIRVEIS_OpenCL:
-      return mapValue(BV, transOCLBuiltinFromExtInst(ExtInst, BB));
+    case SPIRVEIS_OpenCL: {
+      auto *V = mapValue(BV, transOCLBuiltinFromExtInst(ExtInst, BB));
+      applyFPFastMathModeDecorations(BV, static_cast<Instruction *>(V));
+      return V;
+    }
     case SPIRVEIS_Debug:
     case SPIRVEIS_OpenCL_DebugInfo_100:
     case SPIRVEIS_NonSemantic_Shader_DebugInfo_100:

lib/SPIRV/SPIRVUtil.cpp

@@ -787,6 +787,9 @@ CallInst *mutateCallInst(
   NewCI->copyMetadata(*CI);
   NewCI->setAttributes(CI->getAttributes());
   NewCI->setTailCall(CI->isTailCall());
+  if (isa<FPMathOperator>(CI))
+    NewCI->setFastMathFlags(CI->getFastMathFlags());
+
   if (CI->hasFnAttr("fpbuiltin-max-error")) {
     auto Attr = CI->getFnAttr("fpbuiltin-max-error");
     NewCI->addFnAttr(Attr);

lib/SPIRV/SPIRVWriter.cpp

@@ -2715,7 +2715,8 @@ bool LLVMToSPIRVBase::transDecoration(Value *V, SPIRVValue *BV) {
     if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub ||
         Opcode == Instruction::FMul || Opcode == Instruction::FDiv ||
         Opcode == Instruction::FRem ||
-        ((Opcode == Instruction::FNeg || Opcode == Instruction::FCmp) &&
+        ((Opcode == Instruction::FNeg || Opcode == Instruction::FCmp ||
+          BV->isExtInst()) &&
          BM->isAllowedToUseVersion(VersionNumber::SPIRV_1_6))) {
       FastMathFlags FMF = BVF->getFastMathFlags();
       SPIRVWord M{0};
@@ -2742,8 +2743,13 @@ bool LLVMToSPIRVBase::transDecoration(Value *V, SPIRVValue *BV) {
           }
         }
       }
-      if (M != 0)
+      if (M != 0) {
         BV->setFPFastMathMode(M);
+        if (Opcode == Instruction::FNeg || Opcode == Instruction::FCmp ||
+            BV->isExtInst())
+          BM->setMinSPIRVVersion(
+              static_cast<SPIRVWord>(VersionNumber::SPIRV_1_6));
+      }
     }
   }
   if (Instruction *Inst = dyn_cast<Instruction>(V)) {

test/transcoding/fast-math-opencl-builtins.ll

@@ -0,0 +1,41 @@
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv -spirv-text %t.bc -o - | FileCheck %s --check-prefix=CHECK-SPIRV
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r %t.spv -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-LLVM-OCL
+; RUN: llvm-spirv -r --spirv-target-env=SPV-IR %t.spv -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-LLVM-SPV
+
+; RUN: llvm-spirv -spirv-text --spirv-max-version=1.5 %t.bc -o - | FileCheck %s --check-prefix=CHECK-SPIRV-NEG
+
+; CHECK-SPIRV: Decorate [[#FPDec4:]] FPFastMathMode 16
+; CHECK-SPIRV: ExtInst [[#]] [[#FPDec4]] [[#]] fmax [[#]] [[#]]
+
+; CHECK-SPIRV-NEG-NOT: Decorate [[#]] FPFastMathMode [[#]]
+
+; CHECK-LLVM-OCL: call fast spir_func float @_Z4fmaxff(float %[[#]], float %[[#]])
+
+; CHECK-LLVM-SPV: call fast spir_func float @_Z16__spirv_ocl_fmaxff(float %[[#]], float %[[#]])
+
+; ModuleID = 'test.bc'
+source_filename = "test.cpp"
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+target triple = "spir64-unknown-unknown"
+
+@__spirv_BuiltInGlobalInvocationId = external dso_local local_unnamed_addr addrspace(1) constant <3 x i64>, align 32
+
+declare dso_local spir_func noundef float @_Z16__spirv_ocl_fmaxff(float noundef, float noundef) local_unnamed_addr
+
+define weak_odr dso_local spir_kernel void @nofpclass_fast(float addrspace(1)* noundef align 4 %_arg_data, float addrspace(1)* noundef align 4 %_arg_dat1, float addrspace(1)* noundef align 4 %_arg_dat2) local_unnamed_addr  {
+entry:
+  %0 = load <3 x i64>, <3 x i64> addrspace(1)* @__spirv_BuiltInGlobalInvocationId, align 32
+  %elem = extractelement <3 x i64> %0, i32 2
+  %arrayidx.i = getelementptr inbounds float, float addrspace(1)* %_arg_data, i64 %elem
+  %arrayidx3.i = getelementptr inbounds float, float addrspace(1)* %_arg_dat1, i64 %elem
+  %cmp.i = icmp ult i64 %elem, 2147483648
+  %arrayidx5.i = getelementptr inbounds float, float addrspace(1)* %_arg_dat2, i64 %elem
+  %1 = load float, float addrspace(1)* %arrayidx3.i, align 4
+  %2 = load float, float addrspace(1)* %arrayidx5.i, align 4
+  %call.i.i = tail call fast spir_func noundef float @_Z16__spirv_ocl_fmaxff(float noundef %1, float noundef %2)
+  store float %call.i.i, float addrspace(1)* %arrayidx.i, align 4
+  ret void
+}