[cfe-commits] r101222 - in /cfe/trunk: lib/CodeGen/CGExpr.cpp test/CodeGen/bitfield-2.c
Daniel Dunbar
daniel at zuster.org
Tue Apr 13 21:08:03 PDT 2010
Author: ddunbar
Date: Tue Apr 13 23:08:03 2010
New Revision: 101222
URL: http://llvm.org/viewvc/llvm-project?rev=101222&view=rev
Log:
IRgen: Move EmitStoreThroughBitfieldLValue to use new CGBitfieldInfo::AccessInfo decomposition, instead of computing the access policy itself.
- Sadly, this doesn't seem to give any .ll size win so far. It is possible to make this routine significantly smarter & avoid various shifting, masking, and zext/sext, but I'm not really convinced it is worth it. It is tricky, and this is really instcombine's job.
- No intended functionality change; the test case is just to increase coverage & serves as a demo file, it worked before this commit.
Added:
cfe/trunk/test/CodeGen/bitfield-2.c
Modified:
cfe/trunk/lib/CodeGen/CGExpr.cpp
Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=101222&r1=101221&r2=101222&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExpr.cpp Tue Apr 13 23:08:03 2010
@@ -600,21 +600,6 @@
return EmitLoadOfKVCRefLValue(LV, ExprType);
}
-static llvm::Value *getBitFieldAddr(LValue LV, CGBuilderTy &Builder) {
- const CGBitFieldInfo &Info = LV.getBitFieldInfo();
-
- llvm::Value *BaseValue = LV.getBitFieldBaseAddr();
- const llvm::PointerType *BaseTy =
- cast<llvm::PointerType>(BaseValue->getType());
-
- // Cast to the type of the access we will perform.
- llvm::Value *V = Builder.CreateBitCast(
- BaseValue, llvm::PointerType::get(Info.FieldTy, BaseTy->getAddressSpace()));
-
- // Offset by the access index.
- return Builder.CreateConstGEP1_32(V, Info.FieldNo);
-}
-
RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV,
QualType ExprType) {
const CGBitFieldInfo &Info = LV.getBitFieldInfo();
@@ -656,7 +641,7 @@
// Shift out unused low bits and mask out unused high bits.
llvm::Value *Val = Load;
if (AI.FieldBitStart)
- Val = Builder.CreateAShr(Load, AI.FieldBitStart);
+ Val = Builder.CreateLShr(Load, AI.FieldBitStart);
Val = Builder.CreateAnd(Val, llvm::APInt::getLowBitsSet(AI.AccessWidth,
AI.TargetBitWidth),
"bf.clear");
@@ -678,7 +663,7 @@
// FIXME: This can easily be folded into the load of the high bits, which
// could also eliminate the mask of high bits in some situations.
if (Info.isSigned()) {
- unsigned ExtraBits = ResSizeInBits - Info.Size;
+ unsigned ExtraBits = ResSizeInBits - Info.getSize();
if (ExtraBits)
Res = Builder.CreateAShr(Builder.CreateShl(Res, ExtraBits),
ExtraBits, "bf.val.sext");
@@ -805,88 +790,97 @@
QualType Ty,
llvm::Value **Result) {
const CGBitFieldInfo &Info = Dst.getBitFieldInfo();
- unsigned StartBit = Info.Start;
- unsigned BitfieldSize = Info.Size;
- llvm::Value *Ptr = getBitFieldAddr(Dst, Builder);
-
- const llvm::Type *EltTy =
- cast<llvm::PointerType>(Ptr->getType())->getElementType();
- unsigned EltTySize = CGM.getTargetData().getTypeSizeInBits(EltTy);
- // Get the new value, cast to the appropriate type and masked to exactly the
- // size of the bit-field.
+ // Get the output type.
+ const llvm::Type *ResLTy = ConvertType(Ty);
+ unsigned ResSizeInBits = CGM.getTargetData().getTypeSizeInBits(ResLTy);
+
+ // Get the source value, truncated to the width of the bit-field.
llvm::Value *SrcVal = Src.getScalarVal();
- llvm::Value *NewVal = Builder.CreateIntCast(SrcVal, EltTy, false, "tmp");
- llvm::Constant *Mask = llvm::ConstantInt::get(VMContext,
- llvm::APInt::getLowBitsSet(EltTySize, BitfieldSize));
- NewVal = Builder.CreateAnd(NewVal, Mask, "bf.value");
+ SrcVal = Builder.CreateAnd(SrcVal, llvm::APInt::getLowBitsSet(ResSizeInBits,
+ Info.getSize()),
+ "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");
+ const llvm::Type *SrcTy = Src.getScalarVal()->getType();
+ llvm::Value *ReloadVal = Builder.CreateIntCast(SrcVal, SrcTy, false,
+ "bf.reload.val");
// Sign extend if necessary.
- if (Info.IsSigned) {
- 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");
+ if (Info.isSigned()) {
+ unsigned ExtraBits = ResSizeInBits - Info.getSize();
+ if (ExtraBits)
+ ReloadVal = Builder.CreateAShr(Builder.CreateShl(ReloadVal, ExtraBits),
+ ExtraBits, "bf.reload.sext");
}
- *Result = SrcTrunc;
+ *Result = ReloadVal;
}
- // 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.
- unsigned LowBits = std::min(BitfieldSize, EltTySize - StartBit);
- llvm::Value *LowVal = Builder.CreateLoad(Ptr, Dst.isVolatileQualified(),
- "bf.prev.low");
-
- // Compute the mask for zero-ing the low part of this bitfield.
- llvm::Constant *InvMask =
- llvm::ConstantInt::get(VMContext,
- ~llvm::APInt::getBitsSet(EltTySize, StartBit, StartBit + LowBits));
-
- // Compute the new low part as
- // LowVal = (LowVal & InvMask) | (NewVal << StartBit),
- // with the shift of NewVal implicitly stripping the high bits.
- llvm::Value *NewLowVal =
- Builder.CreateShl(NewVal, StartBit, "bf.value.lo");
- LowVal = Builder.CreateAnd(LowVal, InvMask, "bf.prev.lo.cleared");
- LowVal = Builder.CreateOr(LowVal, NewLowVal, "bf.new.lo");
-
- // Write back.
- Builder.CreateStore(LowVal, Ptr, Dst.isVolatileQualified());
-
- // If the low part doesn't cover the bitfield emit a high part.
- if (LowBits < BitfieldSize) {
- unsigned HighBits = BitfieldSize - LowBits;
- llvm::Value *HighPtr = Builder.CreateGEP(Ptr, llvm::ConstantInt::get(
- llvm::Type::getInt32Ty(VMContext), 1), "bf.ptr.hi");
- llvm::Value *HighVal = Builder.CreateLoad(HighPtr,
- Dst.isVolatileQualified(),
- "bf.prev.hi");
-
- // Compute the mask for zero-ing the high part of this bitfield.
- llvm::Constant *InvMask =
- llvm::ConstantInt::get(VMContext, ~llvm::APInt::getLowBitsSet(EltTySize,
- HighBits));
-
- // Compute the new high part as
- // HighVal = (HighVal & InvMask) | (NewVal lshr LowBits),
- // where the high bits of NewVal have already been cleared and the
- // shift stripping the low bits.
- llvm::Value *NewHighVal =
- Builder.CreateLShr(NewVal, LowBits, "bf.value.high");
- HighVal = Builder.CreateAnd(HighVal, InvMask, "bf.prev.hi.cleared");
- HighVal = Builder.CreateOr(HighVal, NewHighVal, "bf.new.hi");
+ // Iterate over the components, writing each piece to memory.
+ for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) {
+ const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i);
+
+ // Get the field pointer.
+ llvm::Value *Ptr = Dst.getBitFieldBaseAddr();
- // Write back.
- Builder.CreateStore(HighVal, HighPtr, Dst.isVolatileQualified());
+ // Only offset by the field index if used, so that incoming values are not
+ // required to be structures.
+ if (AI.FieldIndex)
+ Ptr = Builder.CreateStructGEP(Ptr, AI.FieldIndex, "bf.field");
+
+ // Offset by the byte offset, if used.
+ if (AI.FieldByteOffset) {
+ const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(VMContext);
+ Ptr = Builder.CreateBitCast(Ptr, i8PTy);
+ Ptr = Builder.CreateConstGEP1_32(Ptr, AI.FieldByteOffset,"bf.field.offs");
+ }
+
+ // Cast to the access type.
+ const llvm::Type *PTy = llvm::Type::getIntNPtrTy(VMContext, AI.AccessWidth,
+ Ty.getAddressSpace());
+ Ptr = Builder.CreateBitCast(Ptr, PTy);
+
+ // Extract the piece of the bit-field value to write in this access, shifted
+ // and masked for placement into memory.
+ llvm::Value *Val = SrcVal;
+ if (AI.TargetBitOffset)
+ Val = Builder.CreateLShr(Val, AI.TargetBitOffset);
+ Val = Builder.CreateAnd(Val, llvm::APInt::getLowBitsSet(ResSizeInBits,
+ AI.TargetBitWidth));
+ if (AI.FieldBitStart)
+ Val = Builder.CreateShl(Val, AI.FieldBitStart);
+
+ // Extend or truncate to the access size.
+ const llvm::Type *AccessLTy =
+ llvm::Type::getIntNTy(VMContext, AI.AccessWidth);
+ if (ResSizeInBits < AI.AccessWidth)
+ Val = Builder.CreateZExt(Val, AccessLTy);
+ else if (ResSizeInBits > AI.AccessWidth)
+ Val = Builder.CreateTrunc(Val, AccessLTy);
+
+ // If necessary, load and OR in bits that are outside of the bit-field.
+ if (AI.TargetBitWidth != AI.AccessWidth) {
+ llvm::LoadInst *Load = Builder.CreateLoad(Ptr, Dst.isVolatileQualified());
+ if (AI.AccessAlignment)
+ Load->setAlignment(AI.AccessAlignment);
+
+ // Compute the mask for zeroing the bits that are part of the bit-field.
+ llvm::APInt InvMask =
+ ~llvm::APInt::getBitsSet(AI.AccessWidth, AI.FieldBitStart,
+ AI.FieldBitStart + AI.TargetBitWidth);
+
+ // Apply the mask and OR in to the value to write.
+ Val = Builder.CreateOr(Val, Builder.CreateAnd(Load, InvMask));
+ }
+
+ // Write the value.
+ llvm::StoreInst *Store = Builder.CreateStore(Val, Ptr,
+ Dst.isVolatileQualified());
+ if (AI.AccessAlignment)
+ Store->setAlignment(AI.AccessAlignment);
}
}
Added: cfe/trunk/test/CodeGen/bitfield-2.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/bitfield-2.c?rev=101222&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/bitfield-2.c (added)
+++ cfe/trunk/test/CodeGen/bitfield-2.c Tue Apr 13 23:08:03 2010
@@ -0,0 +1,176 @@
+// RUN: %clang_cc1 -emit-llvm -triple x86_64 -O3 -o - %s | \
+// RUN: FileCheck -check-prefix=CHECK-OPT %s
+
+/****/
+
+// PR6176
+
+struct __attribute((packed)) s0 {
+ int f0 : 24;
+};
+
+struct s0 g0 = { 0xdeadbeef };
+
+int f0_load(struct s0 *a0) {
+ int size_check[sizeof(struct s0) == 3 ? 1 : -1];
+ return a0->f0;
+}
+int f0_store(struct s0 *a0) {
+ return (a0->f0 = 1);
+}
+int f0_reload(struct s0 *a0) {
+ return (a0->f0 += 1);
+}
+
+// CHECK-OPT: define i64 @test_0()
+// CHECK-OPT: ret i64 1
+// CHECK-OPT: }
+unsigned long long test_0() {
+ struct s0 g0 = { 0xdeadbeef };
+ unsigned long long res = 0;
+ res ^= g0.f0;
+ res ^= f0_load(&g0) ^ f0_store(&g0) ^ f0_reload(&g0);
+ res ^= g0.f0;
+ return res;
+}
+
+/****/
+
+// PR5591
+
+#pragma pack(push)
+#pragma pack(1)
+struct __attribute((packed)) s1 {
+ signed f0 : 10;
+ signed f1 : 10;
+};
+#pragma pack(pop)
+
+struct s1 g1 = { 0xdeadbeef, 0xdeadbeef };
+
+int f1_load(struct s1 *a0) {
+ int size_check[sizeof(struct s1) == 3 ? 1 : -1];
+ return a0->f1;
+}
+int f1_store(struct s1 *a0) {
+ return (a0->f1 = 1234);
+}
+int f1_reload(struct s1 *a0) {
+ return (a0->f1 += 1234);
+}
+
+// CHECK-OPT: define i64 @test_1()
+// CHECK-OPT: ret i64 210
+// CHECK-OPT: }
+unsigned long long test_1() {
+ struct s1 g1 = { 0xdeadbeef, 0xdeadbeef };
+ unsigned long long res = 0;
+ res ^= g1.f0 ^ g1.f1;
+ res ^= f1_load(&g1) ^ f1_store(&g1) ^ f1_reload(&g1);
+ res ^= g1.f0 ^ g1.f1;
+ return res;
+}
+
+/****/
+
+// PR5567
+
+union u2 {
+ unsigned long long f0 : 3;
+};
+
+union u2 g2 = { 0xdeadbeef };
+
+int f2_load(union u2 *a0) {
+ return a0->f0;
+}
+int f2_store(union u2 *a0) {
+ return (a0->f0 = 1234);
+}
+int f2_reload(union u2 *a0) {
+ return (a0->f0 += 1234);
+}
+
+// CHECK-OPT: define i64 @test_2()
+// CHECK-OPT: ret i64 2
+// CHECK-OPT: }
+unsigned long long test_2() {
+ union u2 g2 = { 0xdeadbeef };
+ unsigned long long res = 0;
+ res ^= g2.f0;
+ res ^= f2_load(&g2) ^ f2_store(&g2) ^ f2_reload(&g2);
+ res ^= g2.f0;
+ return res;
+}
+
+/***/
+
+// PR5039
+
+struct s3 {
+ long long f0 : 32;
+ long long f1 : 32;
+};
+
+struct s3 g3 = { 0xdeadbeef, 0xdeadbeef };
+
+int f3_load(struct s3 *a0) {
+ a0->f0 = 1;
+ return a0->f0;
+}
+int f3_store(struct s3 *a0) {
+ a0->f0 = 1;
+ return (a0->f0 = 1234);
+}
+int f3_reload(struct s3 *a0) {
+ a0->f0 = 1;
+ return (a0->f0 += 1234);
+}
+
+// CHECK-OPT: define i64 @test_3()
+// CHECK-OPT: ret i64 -559039940
+// CHECK-OPT: }
+unsigned long long test_3() {
+ struct s3 g3 = { 0xdeadbeef, 0xdeadbeef };
+ unsigned long long res = 0;
+ res ^= g3.f0 ^ g3.f1;
+ res ^= f3_load(&g3) ^ f3_store(&g3) ^ f3_reload(&g3);
+ res ^= g3.f0 ^ g3.f1;
+ return res;
+}
+
+/***/
+
+// This is a case where the bitfield access will straddle an alignment boundary
+// of its underlying type.
+
+struct s4 {
+ unsigned f0 : 16;
+ unsigned f1 : 28 __attribute__ ((packed));
+};
+
+struct s4 g4 = { 0xdeadbeef, 0xdeadbeef };
+
+int f4_load(struct s4 *a0) {
+ return a0->f0 ^ a0->f1;
+}
+int f4_store(struct s4 *a0) {
+ return (a0->f0 = 1234) ^ (a0->f1 = 5678);
+}
+int f4_reload(struct s4 *a0) {
+ return (a0->f0 += 1234) ^ (a0->f1 += 5678);
+}
+
+// CHECK-OPT: define i64 @test_4()
+// CHECK-OPT: ret i64 4860
+// CHECK-OPT: }
+unsigned long long test_4() {
+ struct s4 g4 = { 0xdeadbeef, 0xdeadbeef };
+ unsigned long long res = 0;
+ res ^= g4.f0 ^ g4.f1;
+ res ^= f4_load(&g4) ^ f4_store(&g4) ^ f4_reload(&g4);
+ res ^= g4.f0 ^ g4.f1;
+ return res;
+}
+
+/***/
More information about the cfe-commits
mailing list