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Revert r145273 and fix in SelectionDAG::InferPtrAlignment() instead. 

Conservatively returns zero when the GV does not specify an alignment nor is it
initialized. Previously it returns ABI alignment for type of the GV. However, 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.
rdar://10464621

llvm-svn: 145300
This commit is contained in:
Evan Cheng 2011-11-28 22:37:34 +00:00
parent 124d8ff0da
commit 4a5b2040e2
3 changed files with 18 additions and 28 deletions
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38
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -6206,20 +6206,13 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
// Try to infer better alignment information than the load already has.
if (OptLevel != CodeGenOpt::None && LD->isUnindexed()) {
unsigned ABIAlign = TLI.getTargetData()->
getABITypeAlignment(LD->getMemoryVT().getTypeForEVT(*DAG.getContext()));
unsigned LDAlign = LD->getAlignment();
// Do not touch loads with explicit alignments that are smaller than ABI
// alignment to avoid breaking loads from "packed" types.
if (!LDAlign || LDAlign >= ABIAlign) {
if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
if (Align > LDAlign)
return DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
LD->getValueType(0),
Chain, Ptr, LD->getPointerInfo(),
LD->getMemoryVT(),
LD->isVolatile(), LD->isNonTemporal(), Align);
}
if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
if (Align > LD->getAlignment())
return DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
LD->getValueType(0),
Chain, Ptr, LD->getPointerInfo(),
LD->getMemoryVT(),
LD->isVolatile(), LD->isNonTemporal(), Align);
}
}
@ -6676,18 +6669,11 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
// Try to infer better alignment information than the store already has.
if (OptLevel != CodeGenOpt::None && ST->isUnindexed()) {
unsigned ABIAlign = TLI.getTargetData()->
getABITypeAlignment(ST->getMemoryVT().getTypeForEVT(*DAG.getContext()));
unsigned STAlign = ST->getAlignment();
// Do not touch stores with explicit alignments that are smaller than ABI
// alignment to avoid breaking stores from "packed" types.
if (!STAlign || STAlign >= ABIAlign) {
if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
if (Align > STAlign)
return DAG.getTruncStore(Chain, N->getDebugLoc(), Value,
Ptr, ST->getPointerInfo(), ST->getMemoryVT(),
ST->isVolatile(), ST->isNonTemporal(),Align);
}
if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
if (Align > ST->getAlignment())
return DAG.getTruncStore(Chain, N->getDebugLoc(), Value,
Ptr, ST->getPointerInfo(), ST->getMemoryVT(),
ST->isVolatile(), ST->isNonTemporal(), Align);
}
}

6
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -6564,7 +6564,11 @@ unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
}
}
if (!Align)
Align = TLI.getTargetData()->getABITypeAlignment(GV->getType());
// 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);
}

2
llvm/test/CodeGen/X86/widen_load-1.ll
View File

@ -21,7 +21,7 @@ define void @reset(<2 x float>* noalias %garbage1) {
store i32 0, i32* %changed, align 4
%r2 = getelementptr float* bitcast ([20 x i64]* @compl to float*), i64 32 ; <float*> [#uses=1]
%r3 = bitcast float* %r2 to <2 x float>* ; <<2 x float>*> [#uses=1]
%r4 = load <2 x float>* %r3, align 8 ; <<2 x float>> [#uses=1]
%r4 = load <2 x float>* %r3, align 4 ; <<2 x float>> [#uses=1]
call void @killcommon(i32* %changed)
br label %"file complex.c, line 34, bb4"