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Make SelectionDAG::InferPtrAlignment use llvm::ComputeMaskedBits instead of duplicating the logic for globals. Make llvm::ComputeMaskedBits handle GlobalVariables slightly more aggressively, to match what InferPtrAlignment knew how to do.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145304 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2011-11-28 22:48:22 +00:00
parent ed1c0c7f58
commit c4c2a02485
3 changed files with 22 additions and 29 deletions
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18
lib/Analysis/ValueTracking.cpp
View File

@ -103,14 +103,16 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) {
Type *ObjectType = GV->getType()->getElementType();
// If the object is defined in the current Module, we'll be giving
// it the preferred alignment. Otherwise, we have to assume that it
// may only have the minimum ABI alignment.
if (!GV->isDeclaration() && !GV->mayBeOverridden())
Align = TD->getPrefTypeAlignment(ObjectType);
else
Align = TD->getABITypeAlignment(ObjectType);
if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
Type *ObjectType = GVar->getType()->getElementType();
// If the object is defined in the current Module, we'll be giving
// it the preferred alignment. Otherwise, we have to assume that it
// may only have the minimum ABI alignment.
if (!GVar->isDeclaration() && !GVar->mayBeOverridden())
Align = TD->getPreferredAlignment(GVar);
else
Align = TD->getABITypeAlignment(ObjectType);
}
}
if (Align > 0)
KnownZero = Mask & APInt::getLowBitsSet(BitWidth,

27
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -6553,24 +6553,15 @@ unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
const GlobalValue *GV;
int64_t GVOffset = 0;
if (TLI.isGAPlusOffset(Ptr.getNode(), GV, GVOffset)) {
// If GV has specified alignment, then use it. Otherwise, use the preferred
// alignment.
unsigned Align = GV->getAlignment();
if (!Align) {
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
if (GVar->hasInitializer()) {
const TargetData *TD = TLI.getTargetData();
Align = TD->getPreferredAlignment(GVar);
}
}
if (!Align)
// Conservatively returns zero here instead of using ABI alignment for
// type of the GV. If the type is a "packed" type, then the under-
// specified alignments is attached to the load / store instructions.
// In that case, the alignment of the type cannot be trusted.
return 0;
}
return MinAlign(Align, GVOffset);
unsigned PtrWidth = TLI.getPointerTy().getSizeInBits();
APInt AllOnes = APInt::getAllOnesValue(PtrWidth);
APInt KnownZero(PtrWidth, 0), KnownOne(PtrWidth, 0);
llvm::ComputeMaskedBits(const_cast<GlobalValue*>(GV), AllOnes,
KnownZero, KnownOne, TLI.getTargetData());
unsigned AlignBits = KnownZero.countTrailingOnes();
unsigned Align = AlignBits ? 1 << std::min(31U, AlignBits) : 0;
if (Align)
return MinAlign(Align, GVOffset);
}
// If this is a direct reference to a stack slot, use information about the

6
test/Transforms/InstCombine/constant-fold-gep.ll
View File

@ -9,7 +9,7 @@ target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f3
@Y = internal global [3 x %struct.X] zeroinitializer
define void @frob() {
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 0), align 8
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 0), align 16
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 0), align 4
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 1), align 4
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 1), align 4
@ -33,7 +33,7 @@ define void @frob() {
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 10), align 4
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 1, i32 1, i64 2), align 4
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 11), align 4
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 2, i32 0, i64 0), align 8
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 2, i32 0, i64 0), align 16
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 12), align 4
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 2, i32 0, i64 1), align 4
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 13), align 4
@ -47,7 +47,7 @@ define void @frob() {
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 17), align 8
; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 1, i64 0, i32 0, i64 0), align 8
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 18), align 8
; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 2, i64 0, i32 0, i64 0), align 8
; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 2, i64 0, i32 0, i64 0), align 16
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 36), align 8
; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 1, i64 0, i32 0, i64 1), align 8
store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 19), align 8