This patch fixes a bug in method InstCombiner::FoldCmpCstShrCst where we
wrongly computed the distance between the highest bits set of two negative
values.
This fixes PR21222.
Differential Revision: http://reviews.llvm.org/D5700
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219406
91177308-0d34-0410-b5e6-
96231b3b80d8
// Get the distance between the highest bit that's set.
int Shift;
if (IsNegative)
- Shift = (-AP2).logBase2() - (-AP1).logBase2();
+ // Get the ones' complement of AP2 and AP1 when computing the distance.
+ Shift = (~AP2).logBase2() - (~AP1).logBase2();
else
Shift = AP2.logBase2() - AP1.logBase2();
%cmp = icmp ne i32 %shr, -5
ret i1 %cmp
}
+
+; CHECK-LABEL: @PR21222
+; CHECK: icmp eq i32 %B, 6
+define i1 @PR21222(i32 %B) {
+ %shr = ashr i32 -93, %B
+ %cmp = icmp eq i32 %shr, -2
+ ret i1 %cmp
+}