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disallow preinc of a frameindex. This is not profitable and causes 2-addr
pass to explode. This fixes a bunch of llc-beta failures on ppc last night. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31661 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2750,14 +2750,20 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
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if (!TLI.getPreIndexedAddressParts(N, BasePtr, Offset, AM, DAG))
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return false;
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// Try turning it into a pre-indexed load / store except when
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// 1) If N is a store and the ptr is either the same as or is a
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// Try turning it into a pre-indexed load / store except when:
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// 1) The base is a frame index.
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// 2) If N is a store and the ptr is either the same as or is a
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// predecessor of the value being stored.
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// 2) Another use of base ptr is a predecessor of N. If ptr is folded
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// 3) Another use of base ptr is a predecessor of N. If ptr is folded
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// that would create a cycle.
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// 3) All uses are load / store ops that use it as base ptr.
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// 4) All uses are load / store ops that use it as base ptr.
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// Checking #1.
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// Check #1. Preinc'ing a frame index would require copying the stack pointer
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// (plus the implicit offset) to a register to preinc anyway.
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if (isa<FrameIndexSDNode>(BasePtr))
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return false;
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// Check #2.
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if (!isLoad) {
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SDOperand Val = cast<StoreSDNode>(N)->getValue();
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if (Val == Ptr || Ptr.Val->isPredecessor(Val.Val))
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