summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat
-rw-r--r--clang/lib/CodeGen/CGExpr.cpp26
-rw-r--r--clang/lib/CodeGen/CGExprScalar.cpp29
-rw-r--r--clang/lib/CodeGen/CodeGenFunction.h11
-rw-r--r--clang/lib/CodeGen/README.txt5
-rw-r--r--clang/test/CodeGen/bitfield-assign.c44
-rw-r--r--clang/test/CodeGen/volatile.c4
6 files changed, 92 insertions, 27 deletions
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 95733abbab4..9328a535670 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -392,7 +392,8 @@ void CodeGenFunction::EmitStoreThroughLValue(RValue Src, LValue Dst,
}
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 @@ void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
// 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.
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index d87edc3e7b2..b236a6ad31e 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -786,15 +786,14 @@ Value *ScalarExprEmitter::EmitCompoundAssign(const CompoundAssignOperator *E,
// Convert the result back to the LHS type.
Result = EmitScalarConversion(Result, ResultTy, LHSTy);
- // Store the result value into the LHS lvalue.
- CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV, LHSTy);
-
- // For bitfields, we need the value in the bitfield. Note that
- // property references do not reload their value (even though the
- // setter may have changed it).
- // FIXME: This adds an extra bitfield load
+ // Store the result value into the LHS lvalue. Bit-fields are
+ // handled specially because the result is altered by the store.
if (LHSLV.isBitfield())
- Result = EmitLoadOfLValue(LHSLV, LHSTy);
+ CGF.EmitStoreThroughBitfieldLValue(RValue::get(Result), LHSLV, LHSTy,
+ &Result);
+ else
+ CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV, LHSTy);
+
return Result;
}
@@ -1003,16 +1002,14 @@ Value *ScalarExprEmitter::VisitBinAssign(const BinaryOperator *E) {
LValue LHS = EmitLValue(E->getLHS());
Value *RHS = Visit(E->getRHS());
- // Store the value into the LHS.
+ // Store the value into the LHS. Bit-fields are handled specially
+ // because the result is altered by the store.
// FIXME: Volatility!
- CGF.EmitStoreThroughLValue(RValue::get(RHS), LHS, E->getType());
-
- // For bitfields, we need the value in the bitfield. Note that
- // property references do not reload their value (even though the
- // setter may have changed it).
- // FIXME: This adds an extra bitfield load
if (LHS.isBitfield())
- return EmitLoadOfLValue(LHS, E->getLHS()->getType());
+ CGF.EmitStoreThroughBitfieldLValue(RValue::get(RHS), LHS, E->getType(),
+ &RHS);
+ else
+ CGF.EmitStoreThroughLValue(RValue::get(RHS), LHS, E->getType());
// Return the RHS.
return RHS;
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 5d99dba69a8..05b2793456b 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -32,6 +32,7 @@ namespace llvm {
class BasicBlock;
class Module;
class SwitchInst;
+ class Value;
}
namespace clang {
@@ -446,8 +447,16 @@ public:
void EmitStoreThroughLValue(RValue Src, LValue Dst, QualType Ty);
void EmitStoreThroughExtVectorComponentLValue(RValue Src, LValue Dst,
QualType Ty);
- void EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst, QualType Ty);
void EmitStoreThroughPropertyRefLValue(RValue Src, LValue Dst, QualType Ty);
+
+ /// EmitStoreThroughLValue - Store Src into Dst with same
+ /// constraints as EmitStoreThroughLValue.
+ ///
+ /// \param Result [out] - If non-null, this will be set to a Value*
+ /// for the bit-field contents after the store, appropriate for use
+ /// as the result of an assignment to the bit-field.
+ void EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst, QualType Ty,
+ llvm::Value **Result=0);
// Note: only availabe for agg return types
LValue EmitBinaryOperatorLValue(const BinaryOperator *E);
diff --git a/clang/lib/CodeGen/README.txt b/clang/lib/CodeGen/README.txt
index 33fbfdb744a..12a08e161b0 100644
--- a/clang/lib/CodeGen/README.txt
+++ b/clang/lib/CodeGen/README.txt
@@ -17,8 +17,3 @@ appropriately aligned then is is a lot shorter to just load the char
directly.
//===---------------------------------------------------------------------===//
-
-Bitfields should not reload the stored value just to return the
-correct result.
-
-//===---------------------------------------------------------------------===//
diff --git a/clang/test/CodeGen/bitfield-assign.c b/clang/test/CodeGen/bitfield-assign.c
new file mode 100644
index 00000000000..fc163b4d3ba
--- /dev/null
+++ b/clang/test/CodeGen/bitfield-assign.c
@@ -0,0 +1,44 @@
+/* Check that the result of a bitfield assignment is properly
+ truncated and does not generate a redundant load. */
+
+/* Check that we get one load for each simple assign and two for the
+ compound assign (load the old value before the add then load again
+ to store back). Also check that our g0 pattern is good. */
+// RUN: clang -O0 -emit-llvm -o %t %s &&
+// RUN: grep 'load ' %t | count 5 &&
+// RUN: grep "@g0" %t | count 4 &&
+
+// Check that we got the right value.
+// RUN: clang -O3 -emit-llvm -o %t %s &&
+// RUN: grep 'load ' %t | count 0 &&
+// RUN: grep "@g0" %t | count 0
+
+struct s0 {
+ int f0 : 2;
+ _Bool f1 : 1;
+ unsigned f2 : 2;
+};
+
+int g0();
+
+void f0(void) {
+ struct s0 s;
+ if ((s.f0 = 3) != -1) g0();
+}
+
+void f1(void) {
+ struct s0 s;
+ if ((s.f1 = 3) != 1) g0();
+}
+
+void f2(void) {
+ struct s0 s;
+ if ((s.f2 = 3) != 3) g0();
+}
+
+void f3(void) {
+ struct s0 s;
+ // Just check this one for load counts.
+ s.f0 += 3;
+}
+
diff --git a/clang/test/CodeGen/volatile.c b/clang/test/CodeGen/volatile.c
index 4db4a5d8431..ed0a33e9862 100644
--- a/clang/test/CodeGen/volatile.c
+++ b/clang/test/CodeGen/volatile.c
@@ -1,4 +1,4 @@
-// RUN: clang -emit-llvm < %s | grep volatile | count 26
+// RUN: clang -emit-llvm < %s | grep volatile | count 25
// The number 26 comes from the current codegen for volatile loads;
// if this number changes, it's not necessarily something wrong, but
@@ -76,7 +76,7 @@ void main() {
vpF2->x=i;
vF3.x.y=i;
BF.x=i;
- vBF.x=i; // FIXME: This generates an extra volatile load
+ vBF.x=i;
V[3]=i;
vV[3]=i;
OpenPOWER on IntegriCloud