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DAG combine should not increase alignment of loads / stores with alignment less

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than ABI alignment. These are loads / stores from / to "packed" data structures.
Their alignments are intentionally under-specified.

rdar://10301431

llvm-svn: 145273
This commit is contained in:
Evan Cheng 2011-11-28 20:42:56 +00:00
parent 1ed975b097
commit 567aa3dfb3
3 changed files with 66 additions and 13 deletions
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38
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -6206,13 +6206,20 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
// Try to infer better alignment information than the load already has.
if (OptLevel != CodeGenOpt::None && LD->isUnindexed()) {
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);
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);
}
}
}
@ -6669,11 +6676,18 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
// Try to infer better alignment information than the store already has.
if (OptLevel != CodeGenOpt::None && ST->isUnindexed()) {
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);
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);
}
}
}

38
test/CodeGen/ARM/2011-11-28-DAGCombineBug.ll Normal file
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@ -0,0 +1,38 @@
; RUN: llc < %s -mtriple=thumbv7-apple-ios5.0.0 | FileCheck %s
; rdar://10464621
; DAG combine increases loads from packed types. ARM load / store optimizer then
; combined them into a ldm which causes runtime exception.
%struct.InformationBlock = type <{ i32, %struct.FlagBits, %struct.FlagBits }>
%struct.FlagBits = type <{ [4 x i32] }>
@infoBlock = external global %struct.InformationBlock
define hidden void @foo() {
; CHECK: foo:
; CHECK: ldr.w
; CHECK: ldr.w
; CHECK-NOT: ldm
entry:
%tmp13 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 1, i32 0, i32 0), align 1
%tmp15 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 1, i32 0, i32 1), align 1
%tmp17 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 1, i32 0, i32 2), align 1
%tmp19 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 1, i32 0, i32 3), align 1
%tmp = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 2, i32 0, i32 0), align 1
%tmp3 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 2, i32 0, i32 1), align 1
%tmp4 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 2, i32 0, i32 2), align 1
%tmp5 = load i32* getelementptr inbounds (%struct.InformationBlock* @infoBlock, i32 0, i32 2, i32 0, i32 3), align 1
%insert21 = insertvalue [4 x i32] undef, i32 %tmp13, 0
%insert23 = insertvalue [4 x i32] %insert21, i32 %tmp15, 1
%insert25 = insertvalue [4 x i32] %insert23, i32 %tmp17, 2
%insert27 = insertvalue [4 x i32] %insert25, i32 %tmp19, 3
%insert = insertvalue [4 x i32] undef, i32 %tmp, 0
%insert7 = insertvalue [4 x i32] %insert, i32 %tmp3, 1
%insert9 = insertvalue [4 x i32] %insert7, i32 %tmp4, 2
%insert11 = insertvalue [4 x i32] %insert9, i32 %tmp5, 3
tail call void @bar([4 x i32] %insert27, [4 x i32] %insert11)
ret void
}
declare void @bar([4 x i32], [4 x i32])

3
test/CodeGen/X86/widen_load-1.ll
View File

@ -1,5 +1,6 @@
; RUN: llc %s -o - -march=x86-64 -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
; PR4891
; PR5626
; This load should be before the call, not after.
@ -20,7 +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 4 ; <<2 x float>> [#uses=1]
%r4 = load <2 x float>* %r3, align 8 ; <<2 x float>> [#uses=1]
call void @killcommon(i32* %changed)
br label %"file complex.c, line 34, bb4"