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.

llvm-svn: 175270

2 files changed, 42 insertions, 3 deletions

diff --git a/llvm/test/Transforms/InstCombine/exact.ll b/llvm/test/Transforms/InstCombine/exact.ll
index 14741e3c1c3..88ca88c3b92 100644
--- a/llvm/test/Transforms/InstCombine/exact.ll
+++ b/llvm/test/Transforms/InstCombine/exact.ll
@@ -99,9 +99,9 @@ define i1 @ashr_icmp2(i64 %X) nounwind {
 ; PR9998
 ; Make sure we don't transform the ashr here into an sdiv
 ; CHECK: @pr9998
-; CHECK: = and i32 %V, 1
-; CHECK: %Z = icmp ne
-; CHECK: ret i1 %Z
+; CHECK:      [[BIT:%[A-Za-z0-9.]+]] = and i32 %V, 1
+; CHECK-NEXT: [[CMP:%[A-Za-z0-9.]+]] = icmp ne i32 [[BIT]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
 define i1 @pr9998(i32 %V) nounwind {
 entry:
   %W = shl i32 %V, 31
@@ -112,6 +112,7 @@ entry:
 }
 
 
+
 ; CHECK: @udiv_icmp1
 ; CHECK: icmp ne i64 %X, 0
 define i1 @udiv_icmp1(i64 %X) nounwind {
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 8fb6144c3f1..331eb3f21a9 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/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
+}