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disallow preinc of a frameindex. This is not profitable and causes 2-addr

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pass to explode.  This fixes a bunch of llc-beta failures on ppc last night.

llvm-svn: 31661
This commit is contained in:
Chris Lattner 2006-11-11 01:00:15 +00:00
parent bf0c3e3a02
commit edfc824673
1 changed files with 11 additions and 5 deletions
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16
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2750,14 +2750,20 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
if (!TLI.getPreIndexedAddressParts(N, BasePtr, Offset, AM, DAG))
return false;
// Try turning it into a pre-indexed load / store except when
// 1) If N is a store and the ptr is either the same as or is a
// Try turning it into a pre-indexed load / store except when:
// 1) The base is a frame index.
// 2) 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
// 3) Another use of base ptr is a predecessor of N. If ptr is folded
// that would create a cycle.
// 3) All uses are load / store ops that use it as base ptr.
// 4) All uses are load / store ops that use it as base ptr.
// Checking #1.
// Check #1. Preinc'ing a frame index would require copying the stack pointer
// (plus the implicit offset) to a register to preinc anyway.
if (isa<FrameIndexSDNode>(BasePtr))
return false;
// Check #2.
if (!isLoad) {
SDOperand Val = cast<StoreSDNode>(N)->getValue();
if (Val == Ptr || Ptr.Val->isPredecessor(Val.Val))