Teach InstCombine to work with smaller legal types in icmp (shl %v, C1), C2

It enables to work with a smaller constant, which is target friendly for those which can compare to immediates.
It also avoids inserting a shift in favor of a trunc, which can be free on some targets.

This used to work until LLVM-3.1, but regressed with the 3.2 release.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175270 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 38 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index 8fb6144c3f..331eb3f21a 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -706,3 +706,41 @@ define i1 @test69(i32 %c) nounwind uwtable {
   %3 = or i1 %1, %2
   ret i1 %3
 }
+
+; CHECK: @icmp_sext16trunc
+; CHECK-NEXT: %1 = trunc i32 %x to i16
+; CHECK-NEXT: %cmp = icmp slt i16 %1, 36
+define i1 @icmp_sext16trunc(i32 %x) {
+  %trunc = trunc i32 %x to i16
+  %sext = sext i16 %trunc to i32
+  %cmp = icmp slt i32 %sext, 36
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_sext8trunc
+; CHECK-NEXT: %1 = trunc i32 %x to i8
+; CHECK-NEXT: %cmp = icmp slt i8 %1, 36
+define i1 @icmp_sext8trunc(i32 %x) {
+  %trunc = trunc i32 %x to i8
+  %sext = sext i8 %trunc to i32
+  %cmp = icmp slt i32 %sext, 36
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_shl16
+; CHECK-NEXT: %1 = trunc i32 %x to i16
+; CHECK-NEXT: %cmp = icmp slt i16 %1, 36
+define i1 @icmp_shl16(i32 %x) {
+  %shl = shl i32 %x, 16
+  %cmp = icmp slt i32 %shl, 2359296
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_shl24
+; CHECK-NEXT: %1 = trunc i32 %x to i8
+; CHECK-NEXT: %cmp = icmp slt i8 %1, 36
+define i1 @icmp_shl24(i32 %x) {
+  %shl = shl i32 %x, 24
+  %cmp = icmp slt i32 %shl, 603979776
+  ret i1 %cmp
+}