Transform any logical shift of a power of two into an exact/NUW shift when

in a known-non-zero context.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131887 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll
index bded68ac47..d9ac9cbfe9 100644
--- a/test/Transforms/InstCombine/shift.ll
+++ b/test/Transforms/InstCombine/shift.ll
@@ -506,3 +506,24 @@ define i32 @test41(i32 %a, i32 %b) nounwind {
 ; CHECK-NEXT: shl i32 8, %b
 ; CHECK-NEXT: ret i32
 }
+
+define i32 @test42(i32 %a, i32 %b) nounwind {
+  %div = lshr i32 4096, %b    ; must be exact otherwise we'd divide by zero
+  %div2 = udiv i32 %a, %div
+  ret i32 %div2
+; CHECK: @test42
+; CHECK-NEXT: lshr exact i32 4096, %b
+}
+
+define i32 @test43(i32 %a, i32 %b) nounwind {
+  %div = shl i32 4096, %b    ; must be exact otherwise we'd divide by zero
+  %div2 = udiv i32 %a, %div
+  ret i32 %div2
+; CHECK: @test43
+; CHECK-NEXT: add i32 %b, 12
+; CHECK-NEXT: lshr
+; CHECK-NEXT: ret
+}
+
+
+