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[SCEV] Stop blindly propagating inbounds from GEPs to SCEV nodes - #9116
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Natalie Chouinard (sudonatalie) wants to merge 3 commits into
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ScalarEvolution::getGEPExpr previously converted a GEP instruction's inbounds flag into SCEV::FlagNSW on the index-by-size multiplication and base addition. When a GEP is guarded by control flow, its inbounds property may not hold across the entire loop, and attaching no-wrap flags to the resulting recurrence can pollute a globally uniqued SCEVAddRecExpr shared with another value (such as the loop's induction variable), causing IndVarSimplify to fold away live loop exit checks. This resolves the PR23527 FIXME in ScalarEvolution::getGEPExpr, matching createSCEV's handling of Add and Mul and backporting the fix from: llvm/llvm-project@2ca8a3f (PR23527, D109789)
Natalie Chouinard (sudonatalie)
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Steven Perron (s-perron)
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Couple small nits.
Co-authored-by: Chris B <beanz@abolishcrlf.org>
Co-authored-by: Chris B <beanz@abolishcrlf.org>
Natalie Chouinard (sudonatalie)
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ScalarEvolution::getGEPExpr previously converted a GEP instruction's inbounds flag into SCEV::FlagNSW on the index-by-size multiplication and base addition. When a GEP is guarded by control flow, its inbounds property may not hold across the entire loop, and attaching no-wrap flags to the resulting recurrence can pollute a globally uniqued SCEVAddRecExpr shared with another value (such as the loop's induction variable), causing IndVarSimplify to fold away live loop exit checks.
This resolves the PR23527 FIXME in ScalarEvolution::getGEPExpr, matching createSCEV's handling of Add and Mul and backporting the fix from: llvm/llvm-project@2ca8a3f (PR23527, D109789)