[PATCH] D27795: [SCEV] Be less conservative when extending bitwidths for computing ranges.

[Michael Zolotukhin via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL290211: [SCEV] Be less conservative when extending bitwidths for computing ranges. (authored by mzolotukhin).

Changed prior to commit:
  https://reviews.llvm.org/D27795?vs=81519&id=82167#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D27795

Files:
  llvm/trunk/lib/Analysis/ScalarEvolution.cpp


Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -4679,19 +4679,18 @@
 
   MaxBECount = getNoopOrZeroExtend(MaxBECount, Start->getType());
   ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
-  ConstantRange ZExtMaxBECountRange =
-      MaxBECountRange.zextOrTrunc(BitWidth * 2 + 1);
+  ConstantRange ZExtMaxBECountRange = MaxBECountRange.zextOrTrunc(BitWidth * 2);
 
   ConstantRange StepSRange = getSignedRange(Step);
-  ConstantRange SExtStepSRange = StepSRange.sextOrTrunc(BitWidth * 2 + 1);
+  ConstantRange SExtStepSRange = StepSRange.sextOrTrunc(BitWidth * 2);
 
   ConstantRange StartURange = getUnsignedRange(Start);
   ConstantRange EndURange =
       StartURange.add(MaxBECountRange.multiply(StepSRange));
 
   // Check for unsigned overflow.
-  ConstantRange ZExtStartURange = StartURange.zextOrTrunc(BitWidth * 2 + 1);
-  ConstantRange ZExtEndURange = EndURange.zextOrTrunc(BitWidth * 2 + 1);
+  ConstantRange ZExtStartURange = StartURange.zextOrTrunc(BitWidth * 2);
+  ConstantRange ZExtEndURange = EndURange.zextOrTrunc(BitWidth * 2);
   if (ZExtStartURange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
       ZExtEndURange) {
     APInt Min = APIntOps::umin(StartURange.getUnsignedMin(),
@@ -4711,8 +4710,8 @@
   // Check for signed overflow. This must be done with ConstantRange
   // arithmetic because we could be called from within the ScalarEvolution
   // overflow checking code.
-  ConstantRange SExtStartSRange = StartSRange.sextOrTrunc(BitWidth * 2 + 1);
-  ConstantRange SExtEndSRange = EndSRange.sextOrTrunc(BitWidth * 2 + 1);
+  ConstantRange SExtStartSRange = StartSRange.sextOrTrunc(BitWidth * 2);
+  ConstantRange SExtEndSRange = EndSRange.sextOrTrunc(BitWidth * 2);
   if (SExtStartSRange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
       SExtEndSRange) {
     APInt Min =


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