5508a97976
3.5 snapshot (which around 60% of them did).. r203025, r203050, r203054, r203281, r203581, r203719, r203818, r204155, r204304, r205067, r205630, r205738, r207990, r208501. ok matthew@
46 lines
1.9 KiB
Plaintext
46 lines
1.9 KiB
Plaintext
$OpenBSD: patch-lib_Analysis_IVUsers_cpp,v 1.1 2014/07/10 22:46:37 brad Exp $
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r203719
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PR17473: Don't normalize an expression during postinc transformation unless it's
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invertible.
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--- lib/Analysis/IVUsers.cpp.orig Sun Mar 2 21:57:38 2014
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+++ lib/Analysis/IVUsers.cpp Sat Jun 14 03:56:54 2014
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@@ -186,15 +186,34 @@ bool IVUsers::AddUsersImpl(Instruction *I,
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if (AddUserToIVUsers) {
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// Okay, we found a user that we cannot reduce.
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- IVUses.push_back(new IVStrideUse(this, User, I));
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- IVStrideUse &NewUse = IVUses.back();
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+ IVStrideUse &NewUse = AddUser(User, I);
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// Autodetect the post-inc loop set, populating NewUse.PostIncLoops.
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// The regular return value here is discarded; instead of recording
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// it, we just recompute it when we need it.
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+ const SCEV *OriginalISE = ISE;
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ISE = TransformForPostIncUse(NormalizeAutodetect,
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ISE, User, I,
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NewUse.PostIncLoops,
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*SE, *DT);
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+
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+ // PostIncNormalization effectively simplifies the expression under
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+ // pre-increment assumptions. Those assumptions (no wrapping) might not
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+ // hold for the post-inc value. Catch such cases by making sure the
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+ // transformation is invertible.
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+ if (OriginalISE != ISE) {
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+ const SCEV *DenormalizedISE =
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+ TransformForPostIncUse(Denormalize, ISE, User, I,
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+ NewUse.PostIncLoops, *SE, *DT);
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+
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+ // If we normalized the expression, but denormalization doesn't give the
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+ // original one, discard this user.
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+ if (OriginalISE != DenormalizedISE) {
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+ DEBUG(dbgs() << " DISCARDING (NORMALIZATION ISN'T INVERTIBLE): "
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+ << *ISE << '\n');
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+ IVUses.pop_back();
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+ return false;
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+ }
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+ }
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DEBUG(if (SE->getSCEV(I) != ISE)
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dbgs() << " NORMALIZED TO: " << *ISE << '\n');
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}
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