InstSimplify: Improve handling of ashr/lshr

Summary:
Analyze the range of values produced by ashr/lshr cst, %V when it is
being used in an icmp.

Reviewers: nicholas

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D3774

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209000 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 40 insertions, 0 deletions

diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index 0e270bbe0f..1a62e27dd8 100644
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/test/Transforms/InstSimplify/compare.ll
@@ -826,3 +826,43 @@ define i1 @compare_dividend(i32 %a) {
 ; CHECK-LABEL: @compare_dividend
 ; CHECK-NEXT: ret i1 false
 }
+
+define i1 @lshr_ugt_false(i32 %a) {
+  %shr = lshr i32 1, %a
+  %cmp = icmp ugt i32 %shr, 1
+  ret i1 %cmp
+; CHECK-LABEL: @lshr_ugt_false
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @exact_lshr_ugt_false(i32 %a) {
+  %shr = lshr exact i32 30, %a
+  %cmp = icmp ult i32 %shr, 15
+  ret i1 %cmp
+; CHECK-LABEL: @exact_lshr_ugt_false
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @lshr_sgt_false(i32 %a) {
+  %shr = lshr i32 1, %a
+  %cmp = icmp sgt i32 %shr, 1
+  ret i1 %cmp
+; CHECK-LABEL: @lshr_sgt_false
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @ashr_sgt_false(i32 %a) {
+  %shr = ashr i32 -30, %a
+  %cmp = icmp sgt i32 %shr, -1
+  ret i1 %cmp
+; CHECK-LABEL: @ashr_sgt_false
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @exact_ashr_sgt_false(i32 %a) {
+  %shr = ashr exact i32 -30, %a
+  %cmp = icmp sgt i32 %shr, -15
+  ret i1 %cmp
+; CHECK-LABEL: @exact_ashr_sgt_false
+; CHECK-NEXT: ret i1 false
+}