From: Arseniy Obolenskiy <arseniy.obolenskiy@amd.com>
Date: Thu, 9 Jul 2026 18:42:27 +0200
Subject: [03/13] [Backport to 22] Allow FPFastMathMode decoration on OpFmaKHR (#3820)
Origin: upstream, https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/39d3c567ef11eac8f8d8010ab24ebf4123dd1102

Inspired by https://github.com/llvm/llvm-project/pull/206143
---
 lib/SPIRV/SPIRVWriter.cpp              |  2 +-
 test/extensions/KHR/SPV_KHR_fma/fma.ll | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/SPIRV/SPIRVWriter.cpp b/lib/SPIRV/SPIRVWriter.cpp
index eab572d9..2f0b3a46 100644
--- a/lib/SPIRV/SPIRVWriter.cpp
+++ b/lib/SPIRV/SPIRVWriter.cpp
@@ -3203,7 +3203,7 @@ bool LLVMToSPIRVBase::transDecoration(Value *V, SPIRVValue *BV) {
     auto Opcode = BVF->getOpcode();
     if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub ||
         Opcode == Instruction::FMul || Opcode == Instruction::FDiv ||
-        Opcode == Instruction::FRem ||
+        Opcode == Instruction::FRem || BV->getOpCode() == OpFmaKHR ||
         ((Opcode == Instruction::FNeg || Opcode == Instruction::FCmp ||
           BV->isExtInst()) &&
          BM->isAllowedToUseVersion(VersionNumber::SPIRV_1_6))) {
diff --git a/test/extensions/KHR/SPV_KHR_fma/fma.ll b/test/extensions/KHR/SPV_KHR_fma/fma.ll
index 9fadfeb9..2a167079 100644
--- a/test/extensions/KHR/SPV_KHR_fma/fma.ll
+++ b/test/extensions/KHR/SPV_KHR_fma/fma.ll
@@ -7,6 +7,9 @@
 ; RUN: FileCheck < %t.rev.ll %s --check-prefix=CHECK-LLVM
 ; RUN: llvm-spirv -r %t.spv --spirv-target-env=SPV-IR -o - | llvm-dis -o %t.rev.ll
 ; RUN: FileCheck < %t.rev.ll %s --check-prefix=CHECK-LLVM
+; RUN: llvm-spirv %s --spirv-ext=+SPV_KHR_fma -o %t-fmf.spv
+; RUNx: spirv-val %t-fmf.spv
+; RUN: llvm-spirv %t-fmf.spv -to-text -o - | FileCheck %s --check-prefix=CHECK-SPIRV-FMF
 
 ; RUN: llvm-spirv %s -spirv-text -o %t.spt
 ; RUN: FileCheck < %t.spt %s --check-prefix=CHECK-SPIRV-NO-EXT
@@ -25,6 +28,9 @@
 ; CHECK-SPIRV: FmaKHR [[#TYPE_VEC]] [[#]]
 ; CHECK-SPIRV: FmaKHR [[#TYPE_FLOAT]] [[#]]
 
+; CHECK-SPIRV-FMF: Decorate [[#FMF_RES:]] FPFastMathMode 3
+; CHECK-SPIRV-FMF: FmaKHR [[#]] [[#FMF_RES]]
+
 ; CHECK-SPIRV-NO-EXT-NOT: Capability FMAKHR
 ; CHECK-SPIRV-NO-EXT-NOT: Extension "SPV_KHR_fma"
 ; CHECK-SPIRV-NO-EXT: TypeFloat [[#TYPE_FLOAT:]] 32
@@ -66,6 +72,12 @@ entry:
   ret float %result
 }
 
+define spir_func float @test_fma_fast_math(float %a, float %b, float %c) {
+entry:
+  %result = call nnan ninf float @llvm.fma.f32(float %a, float %b, float %c)
+  ret float %result
+}
+
 declare float @llvm.fma.f32(float, float, float)
 declare <4 x float> @llvm.fma.v4f32(<4 x float>, <4 x float>, <4 x float>)
 declare spir_func float @_Z15__spirv_ocl_fmafff(float, float, float)
-- 
2.55.0