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

[Nathan Gauër via llvm-commits]

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@@ -2078,6 +2249,109 @@ static void patchPhis(const Module &M, SPIRVGlobalRegistry *GR,
   }
 }
 
+static SmallVector<SPIRV::FPFastMathDefaultInfo, 3> &
+getOrCreateFPFastMathDefaultInfoVec(const Module &M,
+                                    SPIRV::ModuleAnalysisInfo &MAI,
+                                    const Function *F) {
+  auto it = MAI.FPFastMathDefaultInfoMap.find(F);
+  if (it != MAI.FPFastMathDefaultInfoMap.end())
+    return it->second;
+
+  // If the map does not contain the entry, create a new one. Initialize it to
+  // contain all 3 elements sorted by bit width of target type: {half, float,
+  // double}.
+  SmallVector<SPIRV::FPFastMathDefaultInfo, 3> FPFastMathDefaultInfoVec;
+  FPFastMathDefaultInfoVec.emplace_back(Type::getHalfTy(M.getContext()),
+                                        SPIRV::FPFastMathMode::None);
+  FPFastMathDefaultInfoVec.emplace_back(Type::getFloatTy(M.getContext()),
+                                        SPIRV::FPFastMathMode::None);
+  FPFastMathDefaultInfoVec.emplace_back(Type::getDoubleTy(M.getContext()),
+                                        SPIRV::FPFastMathMode::None);
+  return MAI.FPFastMathDefaultInfoMap[F] = std::move(FPFastMathDefaultInfoVec);
+}
+
+static SPIRV::FPFastMathDefaultInfo &getFPFastMathDefaultInfo(
+    SmallVector<SPIRV::FPFastMathDefaultInfo, 3> &FPFastMathDefaultInfoVec,
+    const Type *Ty) {
+  size_t BitWidth = Ty->getScalarSizeInBits();
+  int Index = computeFPFastMathDefaultInfoVecIndex(BitWidth);
+  assert(Index >= 0 && Index < 3 &&
+         "Expected FPFastMathDefaultInfo for half, float, or double");
+  assert(FPFastMathDefaultInfoVec.size() == 3 &&
+         "Expected FPFastMathDefaultInfoVec to have exactly 3 elements");
+  return FPFastMathDefaultInfoVec[Index];
+}
+
+static void collectFPFastMathDefaults(const Module &M,
+                                      SPIRV::ModuleAnalysisInfo &MAI,
+                                      const SPIRVSubtarget &ST) {
+  if (!ST.canUseExtension(SPIRV::Extension::SPV_KHR_float_controls2))
+    return;
+
+  // Store the FPFastMathDefaultInfo in the FPFastMathDefaultInfoMap.
+  // We need the entry point (function) as the key, and the target
+  // type and flags as the value.
+  // We also need to check ContractionOff and SignedZeroInfNanPreserve
+  // execution modes, as they are now deprecated and must be replaced
+  // with FPFastMathDefaultInfo.
+  auto Node = M.getNamedMetadata("spirv.ExecutionMode");
+  if (Node) {
----------------
Keenuts wrote:

nit: flip
```suggestion
  if (!Node)
      return;
```

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