InstSimplify: Optimize signed icmp of -(zext V)
Summary:
We know that -(zext V) will always be <= zero, simplify signed icmps
that have these.
Uncovered using http://www.cs.utah.edu/~regehr/souper/
Reviewers: nicholas
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D3754
llvm-svn: 208809
diff --git a/llvm/test/Transforms/InstSimplify/compare.ll b/llvm/test/Transforms/InstSimplify/compare.ll
index ee6be04..76cff90 100644
--- a/llvm/test/Transforms/InstSimplify/compare.ll
+++ b/llvm/test/Transforms/InstSimplify/compare.ll
@@ -757,3 +757,63 @@
; CHECK-LABEL: @vectorselectfold
; CHECK-NEXT: ret <4 x i8> %a
}
+
+define i1 @compare_always_true_slt(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp slt i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_true_slt
+; CHECK-NEXT: ret i1 true
+}
+
+define i1 @compare_always_true_sle(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sle i32 %2, 0
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_true_sle
+; CHECK-NEXT: ret i1 true
+}
+
+define i1 @compare_always_false_sgt(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sgt i32 %2, 0
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_sgt
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_sge(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sge i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_sge
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_eq(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp eq i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_eq
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_ne(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp ne i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_ne
+; CHECK-NEXT: ret i1 true
+}