[clang] Don't do casting of atomic FP loads/stores in FE. (PR #83446)

[Matt Arsenault via cfe-commits]

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@@ -1953,13 +1966,22 @@ void CodeGenFunction::EmitAtomicStore(RValue rvalue, LValue dest,
     }
 
     // Okay, we're doing this natively.
-    llvm::Value *intValue = atomics.convertRValueToInt(rvalue);
+    llvm::Value *ValToStore =
+        atomics.convertRValueToInt(rvalue, /*CastFP=*/false);
 
     // Do the atomic store.
-    Address addr = atomics.castToAtomicIntPointer(atomics.getAtomicAddress());
-    intValue = Builder.CreateIntCast(
-        intValue, addr.getElementType(), /*isSigned=*/false);
-    llvm::StoreInst *store = Builder.CreateStore(intValue, addr);
+    Address Addr = atomics.getAtomicAddress();
+    bool ShouldCastToInt = true;
+    if (llvm::Value *Value = atomics.getScalarRValValueOrNull(rvalue))
+      if (isa<llvm::IntegerType>(Value->getType()) ||
+          Value->getType()->isIEEELikeFPTy())
+        ShouldCastToInt = false;
+    if (ShouldCastToInt) {
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arsenm wrote:

Factoring this into a shouldCastToInt helper function would be better, but it matters little if you're just going to remove this soon anyway 

https://github.com/llvm/llvm-project/pull/83446