Fix redundant load of bit-fields on assignment (to get the updated
value).
- Use extra argument to EmitStoreThroughLValue to provide place to
write update bit-field value if caller requires it.
- This fixes several FIXMEs.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59615 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 95733ab..9328a53 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -392,7 +392,8 @@
}
void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
- QualType Ty) {
+ QualType Ty,
+ llvm::Value **Result) {
unsigned StartBit = Dst.getBitfieldStartBit();
unsigned BitfieldSize = Dst.getBitfieldSize();
llvm::Value *Ptr = Dst.getBitfieldAddr();
@@ -403,12 +404,31 @@
// Get the new value, cast to the appropriate type and masked to
// exactly the size of the bit-field.
- llvm::Value *NewVal = Src.getScalarVal();
- NewVal = Builder.CreateIntCast(NewVal, EltTy, false, "tmp");
+ llvm::Value *SrcVal = Src.getScalarVal();
+ llvm::Value *NewVal = Builder.CreateIntCast(SrcVal, EltTy, false, "tmp");
llvm::Constant *Mask =
llvm::ConstantInt::get(llvm::APInt::getLowBitsSet(EltTySize, BitfieldSize));
NewVal = Builder.CreateAnd(NewVal, Mask, "bf.value");
+ // Return the new value of the bit-field, if requested.
+ if (Result) {
+ // Cast back to the proper type for result.
+ const llvm::Type *SrcTy = SrcVal->getType();
+ llvm::Value *SrcTrunc = Builder.CreateIntCast(NewVal, SrcTy, false,
+ "bf.reload.val");
+
+ // Sign extend if necessary.
+ if (Dst.isBitfieldSigned()) {
+ unsigned SrcTySize = CGM.getTargetData().getTypeSizeInBits(SrcTy);
+ llvm::Value *ExtraBits = llvm::ConstantInt::get(SrcTy,
+ SrcTySize - BitfieldSize);
+ SrcTrunc = Builder.CreateAShr(Builder.CreateShl(SrcTrunc, ExtraBits),
+ ExtraBits, "bf.reload.sext");
+ }
+
+ *Result = SrcTrunc;
+ }
+
// In some cases the bitfield may straddle two memory locations.
// Emit the low part first and check to see if the high needs to be
// done.