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Fix combiner-aa issue with bases which are different, but can alias.

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Previously, it treated GV+28 GV+0 as different bases, and assumed they could
not alias.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82753 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2009-09-25 06:05:26 +00:00
parent 6263778d2c
commit cc66cdd79c
1 changed files with 34 additions and 14 deletions
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48
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -6089,11 +6089,12 @@ SDValue DAGCombiner::BuildUDIV(SDNode *N) {
return S;
}
/// FindBaseOffset - Return true if base is known not to alias with anything
/// but itself. Provides base object and offset as results.
static bool FindBaseOffset(SDValue Ptr, SDValue &Base, int64_t &Offset) {
/// FindBaseOffset - Return true if base is a frame index, which is known not
// to alias with anything but itself. Provides base object and offset as results.
static bool FindBaseOffset(SDValue Ptr, SDValue &Base, int64_t &Offset,
GlobalValue *&GV, void *&CV) {
// Assume it is a primitive operation.
Base = Ptr; Offset = 0;
Base = Ptr; Offset = 0; GV = 0; CV = 0;
// If it's an adding a simple constant then integrate the offset.
if (Base.getOpcode() == ISD::ADD) {
@ -6102,11 +6103,27 @@ static bool FindBaseOffset(SDValue Ptr, SDValue &Base, int64_t &Offset) {
Offset += C->getZExtValue();
}
}
// Return the underlying GlobalValue, and update the Offset. Return false
// for GlobalAddressSDNode since the same GlobalAddress may be represented
// by multiple nodes with different offsets.
if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Base)) {
GV = G->getGlobal();
Offset += G->getOffset();
return false;
}
// Return the underlying Constant value, and update the Offset. Return false
// for ConstantSDNodes since the same constant pool entry may be represented
// by multiple nodes with different offsets.
if (ConstantPoolSDNode *C = dyn_cast<ConstantPoolSDNode>(Base)) {
CV = C->isMachineConstantPoolEntry() ? (void *)C->getMachineCPVal()
: (void *)C->getConstVal();
Offset += C->getOffset();
return false;
}
// If it's any of the following then it can't alias with anything but itself.
return isa<FrameIndexSDNode>(Base) ||
isa<ConstantPoolSDNode>(Base) ||
isa<GlobalAddressSDNode>(Base);
return isa<FrameIndexSDNode>(Base);
}
/// isAlias - Return true if there is any possibility that the two addresses
@ -6123,16 +6140,19 @@ bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1,
// Gather base node and offset information.
SDValue Base1, Base2;
int64_t Offset1, Offset2;
bool KnownBase1 = FindBaseOffset(Ptr1, Base1, Offset1);
bool KnownBase2 = FindBaseOffset(Ptr2, Base2, Offset2);
GlobalValue *GV1, *GV2;
void *CV1, *CV2;
bool isFrameIndex1 = FindBaseOffset(Ptr1, Base1, Offset1, GV1, CV1);
bool isFrameIndex2 = FindBaseOffset(Ptr2, Base2, Offset2, GV2, CV2);
// If they have a same base address then...
if (Base1 == Base2)
// Check to see if the addresses overlap.
// If they have a same base address then check to see if they overlap.
if (Base1 == Base2 || (GV1 && (GV1 == GV2)) || (CV1 && (CV1 == CV2)))
return !((Offset1 + Size1) <= Offset2 || (Offset2 + Size2) <= Offset1);
// If we know both bases then they can't alias.
if (KnownBase1 && KnownBase2) return false;
// If we know what the bases are, and they aren't identical, then we know they
// cannot alias.
if ((isFrameIndex1 || CV1 || GV1) && (isFrameIndex2 || CV2 || GV2))
return false;
// If we know required SrcValue1 and SrcValue2 have relatively large alignment
// compared to the size and offset of the access, we may be able to prove they