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SCEVExpander fixes. Affects LSR and indvars.

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LSR has gradually been improved to more aggressively reuse existing code, particularly existing phi cycles. This exposed problems with the SCEVExpander's sloppy treatment of its insertion point. I applied some rigor to the insertion point problem that will hopefully avoid an endless bug cycle in this area. Changes:

- Always used properlyDominates to check safe code hoisting.

- The insertion point provided to SCEV is now considered a lower bound. This is usually a block terminator or the use itself. Under no cirumstance may SCEVExpander insert below this point.

- LSR is reponsible for finding a "canonical" insertion point across expansion of different expressions.

- Robust logic to determine whether IV increments are in "expanded" form and/or can be safely hoisted above some insertion point.

Fixes PR11783: SCEVExpander assert.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148535 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2012-01-20 07:41:13 +00:00
parent 0e2037ba2b
commit b5c26ef9da
6 changed files with 203 additions and 146 deletions
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8
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -846,7 +846,7 @@ protected:
const SCEVAddRecExpr* GetExtendedOperandRecurrence(NarrowIVDefUse DU);
Instruction *WidenIVUse(NarrowIVDefUse DU);
Instruction *WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter);
void pushNarrowIVUsers(Instruction *NarrowDef, Instruction *WideDef);
};
@ -990,7 +990,7 @@ const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
/// WidenIVUse - Determine whether an individual user of the narrow IV can be
/// widened. If so, return the wide clone of the user.
Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU) {
Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
// Stop traversing the def-use chain at inner-loop phis or post-loop phis.
if (isa<PHINode>(DU.NarrowUse) &&
@ -1058,7 +1058,7 @@ Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU) {
// NarrowUse.
Instruction *WideUse = 0;
if (WideAddRec == WideIncExpr
&& SCEVExpander::hoistStep(WideInc, DU.NarrowUse, DT))
&& Rewriter.hoistIVInc(WideInc, DU.NarrowUse))
WideUse = WideInc;
else {
WideUse = CloneIVUser(DU);
@ -1163,7 +1163,7 @@ PHINode *WidenIV::CreateWideIV(SCEVExpander &Rewriter) {
// Process a def-use edge. This may replace the use, so don't hold a
// use_iterator across it.
Instruction *WideUse = WidenIVUse(DU);
Instruction *WideUse = WidenIVUse(DU, Rewriter);
// Follow all def-use edges from the previous narrow use.
if (WideUse)