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When forming a pre-indexed store, make sure ptr isn't the same or is a pred of value being stored. It would cause a cycle.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31631 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2006-11-10 08:28:11 +00:00
parent a8423c1898
commit a7ff64d608
1 changed files with 16 additions and 7 deletions
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23
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -214,11 +214,20 @@ namespace {
ISD::MemIndexedMode AM = ISD::UNINDEXED;
if (TLI.getPreIndexedAddressParts(N, BasePtr, Offset, AM, DAG)) {
// Try turning it into a pre-indexed load / store except when
// 1) Another use of base ptr is a predecessor of N. If ptr is folded
// 1) If N is a store and the ptr is either the same as or is a
// predecessor of the value being stored.
// 2) Another use of base ptr is a predecessor of N. If ptr is folded
// that would create a cycle.
// 2) All uses are load / store ops that use it as base ptr.
// 3) All uses are load / store ops that use it as base ptr.
// Now check for #1 and #2.
// Checking #1.
if (!isLoad) {
SDOperand Val = cast<StoreSDNode>(N)->getValue();
if (Val == Ptr || Ptr.Val->isPredecessor(Val.Val))
return false;
}
// Now check for #2 and #3.
bool RealUse = false;
for (SDNode::use_iterator I = Ptr.Val->use_begin(),
E = Ptr.Val->use_end(); I != E; ++I) {
@ -323,12 +332,12 @@ namespace {
continue;
// Try turning it into a post-indexed load / store except when
// 1) Op must be independent of N, i.e. Op is neither a predecessor
// 1) All uses are load / store ops that use it as base ptr.
// 2) Op must be independent of N, i.e. Op is neither a predecessor
// nor a successor of N. Otherwise, if Op is folded that would
// create a cycle.
// 2) All uses are load / store ops that use it as base ptr.
// Check for #3.
// Check for #1.
bool TryNext = false;
for (SDNode::use_iterator II = BasePtr.Val->use_begin(),
EE = BasePtr.Val->use_end(); II != EE; ++II) {
@ -359,7 +368,7 @@ namespace {
if (TryNext)
continue;
// Check for #1
// Check for #2
if (!Op->isPredecessor(N) && !N->isPredecessor(Op)) {
SDOperand Result = isLoad
? DAG.getIndexedLoad(SDOperand(N,0), BasePtr, Offset, AM)