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[DAGCombiner] Respect volatility when checking for aliases

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Making useAA() default to true for SystemZ showed that the combiner alias
analysis wasn't handling volatile accesses.  This hit many of the SystemZ
tests, but I arbitrarily picked one for the purpose of this patch.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193518 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Richard Sandiford 2013-10-28 12:00:00 +00:00
parent 66589dcc8f
commit a7be36c8eb
2 changed files with 27 additions and 19 deletions
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43
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -296,11 +296,11 @@ namespace {
/// isAlias - Return true if there is any possibility that the two addresses
/// overlap.
bool isAlias(SDValue Ptr1, int64_t Size1,
bool isAlias(SDValue Ptr1, int64_t Size1, bool IsVolatile1,
const Value *SrcValue1, int SrcValueOffset1,
unsigned SrcValueAlign1,
const MDNode *TBAAInfo1,
SDValue Ptr2, int64_t Size2,
SDValue Ptr2, int64_t Size2, bool IsVolatile2,
const Value *SrcValue2, int SrcValueOffset2,
unsigned SrcValueAlign2,
const MDNode *TBAAInfo2) const;
@ -312,7 +312,7 @@ namespace {
/// FindAliasInfo - Extracts the relevant alias information from the memory
/// node. Returns true if the operand was a load.
bool FindAliasInfo(SDNode *N,
SDValue &Ptr, int64_t &Size,
SDValue &Ptr, int64_t &Size, bool &IsVolatile,
const Value *&SrcValue, int &SrcValueOffset,
unsigned &SrcValueAlignment,
const MDNode *&TBAAInfo) const;
@ -10789,17 +10789,20 @@ static bool FindBaseOffset(SDValue Ptr, SDValue &Base, int64_t &Offset,
/// isAlias - Return true if there is any possibility that the two addresses
/// overlap.
bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1,
bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1, bool IsVolatile1,
const Value *SrcValue1, int SrcValueOffset1,
unsigned SrcValueAlign1,
const MDNode *TBAAInfo1,
SDValue Ptr2, int64_t Size2,
SDValue Ptr2, int64_t Size2, bool IsVolatile2,
const Value *SrcValue2, int SrcValueOffset2,
unsigned SrcValueAlign2,
const MDNode *TBAAInfo2) const {
// If they are the same then they must be aliases.
if (Ptr1 == Ptr2) return true;
// If they are both volatile then they cannot be reordered.
if (IsVolatile1 && IsVolatile2) return true;
// Gather base node and offset information.
SDValue Base1, Base2;
int64_t Offset1, Offset2;
@ -10865,24 +10868,25 @@ bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1,
bool DAGCombiner::isAlias(LSBaseSDNode *Op0, LSBaseSDNode *Op1) {
SDValue Ptr0, Ptr1;
int64_t Size0, Size1;
bool IsVolatile0, IsVolatile1;
const Value *SrcValue0, *SrcValue1;
int SrcValueOffset0, SrcValueOffset1;
unsigned SrcValueAlign0, SrcValueAlign1;
const MDNode *SrcTBAAInfo0, *SrcTBAAInfo1;
FindAliasInfo(Op0, Ptr0, Size0, SrcValue0, SrcValueOffset0,
FindAliasInfo(Op0, Ptr0, Size0, IsVolatile0, SrcValue0, SrcValueOffset0,
SrcValueAlign0, SrcTBAAInfo0);
FindAliasInfo(Op1, Ptr1, Size1, SrcValue1, SrcValueOffset1,
FindAliasInfo(Op1, Ptr1, Size1, IsVolatile1, SrcValue1, SrcValueOffset1,
SrcValueAlign1, SrcTBAAInfo1);
return isAlias(Ptr0, Size0, SrcValue0, SrcValueOffset0,
return isAlias(Ptr0, Size0, IsVolatile0, SrcValue0, SrcValueOffset0,
SrcValueAlign0, SrcTBAAInfo0,
Ptr1, Size1, SrcValue1, SrcValueOffset1,
Ptr1, Size1, IsVolatile1, SrcValue1, SrcValueOffset1,
SrcValueAlign1, SrcTBAAInfo1);
}
/// FindAliasInfo - Extracts the relevant alias information from the memory
/// node. Returns true if the operand was a load.
/// node. Returns true if the operand was a nonvolatile load.
bool DAGCombiner::FindAliasInfo(SDNode *N,
SDValue &Ptr, int64_t &Size,
SDValue &Ptr, int64_t &Size, bool &IsVolatile,
const Value *&SrcValue,
int &SrcValueOffset,
unsigned &SrcValueAlign,
@ -10891,11 +10895,12 @@ bool DAGCombiner::FindAliasInfo(SDNode *N,
Ptr = LS->getBasePtr();
Size = LS->getMemoryVT().getSizeInBits() >> 3;
IsVolatile = LS->isVolatile();
SrcValue = LS->getSrcValue();
SrcValueOffset = LS->getSrcValueOffset();
SrcValueAlign = LS->getOriginalAlignment();
TBAAInfo = LS->getTBAAInfo();
return isa<LoadSDNode>(LS);
return isa<LoadSDNode>(LS) && !IsVolatile;
}
/// GatherAllAliases - Walk up chain skipping non-aliasing memory nodes,
@ -10908,12 +10913,13 @@ void DAGCombiner::GatherAllAliases(SDNode *N, SDValue OriginalChain,
// Get alias information for node.
SDValue Ptr;
int64_t Size;
bool IsVolatile;
const Value *SrcValue;
int SrcValueOffset;
unsigned SrcValueAlign;
const MDNode *SrcTBAAInfo;
bool IsLoad = FindAliasInfo(N, Ptr, Size, SrcValue, SrcValueOffset,
SrcValueAlign, SrcTBAAInfo);
bool IsLoad = FindAliasInfo(N, Ptr, Size, IsVolatile, SrcValue,
SrcValueOffset, SrcValueAlign, SrcTBAAInfo);
// Starting off.
Chains.push_back(OriginalChain);
@ -10954,20 +10960,21 @@ void DAGCombiner::GatherAllAliases(SDNode *N, SDValue OriginalChain,
// Get alias information for Chain.
SDValue OpPtr;
int64_t OpSize;
bool OpIsVolatile;
const Value *OpSrcValue;
int OpSrcValueOffset;
unsigned OpSrcValueAlign;
const MDNode *OpSrcTBAAInfo;
bool IsOpLoad = FindAliasInfo(Chain.getNode(), OpPtr, OpSize,
OpSrcValue, OpSrcValueOffset,
OpIsVolatile, OpSrcValue, OpSrcValueOffset,
OpSrcValueAlign,
OpSrcTBAAInfo);
// If chain is alias then stop here.
if (!(IsLoad && IsOpLoad) &&
isAlias(Ptr, Size, SrcValue, SrcValueOffset, SrcValueAlign,
SrcTBAAInfo,
OpPtr, OpSize, OpSrcValue, OpSrcValueOffset,
isAlias(Ptr, Size, IsVolatile, SrcValue, SrcValueOffset,
SrcValueAlign, SrcTBAAInfo,
OpPtr, OpSize, OpIsVolatile, OpSrcValue, OpSrcValueOffset,
OpSrcValueAlign, OpSrcTBAAInfo)) {
Aliases.push_back(Chain);
} else {

3
test/CodeGen/SystemZ/bswap-02.ll
View File

@ -1,6 +1,7 @@
; Test 32-bit byteswaps from memory to registers.
;
; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
; RUN: llc < %s -mtriple=s390x-linux-gnu -combiner-alias-analysis \
; RUN: -combiner-global-alias-analysis | FileCheck %s
declare i32 @llvm.bswap.i32(i32 %a)