[clang] [Clang] Add support for fp when using min_fetch/max_fetch atomics (PR #160330)

[Eli Friedman via cfe-commits]

================
@@ -507,6 +507,17 @@ static llvm::Value *EmitPostAtomicMinMax(CGBuilderTy &Builder,
                                          bool IsSigned,
                                          llvm::Value *OldVal,
                                          llvm::Value *RHS) {
+  const bool IsFP = OldVal->getType()->isFloatingPointTy();
+
+  if (IsFP) {
+    llvm::Intrinsic::ID IID = (Op == AtomicExpr::AO__atomic_max_fetch ||
+                               Op == AtomicExpr::AO__scoped_atomic_max_fetch)
+                                  ? llvm::Intrinsic::maxnum
+                                  : llvm::Intrinsic::minnum;
+
+    return Builder.CreateBinaryIntrinsic(IID, OldVal, RHS, nullptr, "newval");
----------------
efriedma-quic wrote:

```suggestion
    return Builder.CreateBinaryIntrinsic(IID, OldVal, RHS, FMFSource(), "newval");
```

nullptr technically works, but it unclear what the type of the value is supposed to be.

https://github.com/llvm/llvm-project/pull/160330