[clang] [clang] Lower modf builtin using `llvm.modf` intrinsic (PR #126750)

[Eli Friedman via cfe-commits]

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@@ -859,6 +859,24 @@ static void emitSincosBuiltin(CodeGenFunction &CGF, const CallExpr *E,
   StoreCos->setMetadata(LLVMContext::MD_noalias, AliasScopeList);
 }
 
+static llvm::Value *emitModfBuiltin(CodeGenFunction &CGF, const CallExpr *E,
+                                    llvm::Intrinsic::ID IntrinsicID) {
+  llvm::Value *Val = CGF.EmitScalarExpr(E->getArg(0));
+  llvm::Value *IntPartDest = CGF.EmitScalarExpr(E->getArg(1));
+
+  llvm::Value *Call =
+      CGF.Builder.CreateIntrinsic(IntrinsicID, {Val->getType()}, Val);
+
+  llvm::Value *FractionalResult = CGF.Builder.CreateExtractValue(Call, 0);
+  llvm::Value *IntegralResult = CGF.Builder.CreateExtractValue(Call, 1);
+
+  QualType DestPtrType = E->getArg(1)->getType()->getPointeeType();
+  LValue IntegralLV = CGF.MakeNaturalAlignAddrLValue(IntPartDest, DestPtrType);
+  CGF.Builder.CreateStore(IntegralResult, IntegralLV.getAddress());
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efriedma-quic wrote:

EmitStoreThroughLValue?

https://github.com/llvm/llvm-project/pull/126750