Use ScalarEvolution's new GetMinSignBits and GetMinLeadingZeros
in the loop backedge-taken count computation of the maximum
possible trip count.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73805 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 2dab2f3..465807e 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -3836,9 +3836,12 @@
: getUMaxExpr(RHS, Start);
// Determine the maximum constant end value.
- SCEVHandle MaxEnd = isa<SCEVConstant>(End) ? End :
- getConstant(isSigned ? APInt::getSignedMaxValue(BitWidth) :
- APInt::getMaxValue(BitWidth));
+ SCEVHandle MaxEnd =
+ isa<SCEVConstant>(End) ? End :
+ getConstant(isSigned ? APInt::getSignedMaxValue(BitWidth)
+ .ashr(GetMinSignBits(End) - 1) :
+ APInt::getMaxValue(BitWidth)
+ .lshr(GetMinLeadingZeros(End)));
// Finally, we subtract these two values and divide, rounding up, to get
// the number of times the backedge is executed.