[PATCH] D35256: [SCEV] Try harder to preserve NSW information for sext(sub) expressions

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy requested changes to this revision.
sanjoy added inline comments.
This revision now requires changes to proceed.


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Comment at: lib/Analysis/ScalarEvolution.cpp:5964
+      if (BO->Opcode == Instruction::Sub && BO->Op) {
+        SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op);
+        if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) {
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Why not use `BO->IsNSW`?


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Comment at: test/Analysis/ScalarEvolution/flags-from-poison.ll:612
 ; CHECK: %index64 =
-; CHECK: --> {(sext i32 (-1 * %sub) to i64),+,1}<nsw>
+; CHECK: --> {(-1 * (sext i32 %sub to i64))<nsw>,+,1}<nsw
   %index64 = sext i32 %index32 to i64
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Please add a test case that uses `Intrinsic::ssub_with_overflow`. 


Repository:
  rL LLVM

https://reviews.llvm.org/D35256