From 1fae19555797cad0af7db788a30dd4cc2bc63f6c Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Sun, 14 Apr 2013 21:15:43 +0000
Subject: Reorders two transforms that collide with each other

One performs: (X == 13 | X == 14) -> X-13 <u 2
The other: (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1

The problem is that there are certain values of C1 and C2 that
trigger both transforms but the first one blocks out the second,
this generates suboptimal code.

Reordering the transforms should be better in every case and
allows us to do interesting stuff like turn:
  %shr = lshr i32 %X, 4
  %and = and i32 %shr, 15
  %add = add i32 %and, -14
  %tobool = icmp ne i32 %add, 0

into:
  %and = and i32 %X, 240
  %tobool = icmp ne i32 %and, 224

llvm-svn: 179493
---
 llvm/test/Transforms/InstCombine/icmp.ll | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'llvm/test/Transforms/InstCombine/icmp.ll')

diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 74adbba42b4..c912a576c3d 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -964,3 +964,15 @@ define i1 @icmp_and_shl_neg_eq_0(i32 %A, i32 %B) {
   %cmp = icmp eq i32 %and, 0
   ret i1 %cmp
 }
+
+; CHECK: @icmp_add_and_shr_ne_0
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %X, 240
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp ne i32 [[AND]], 224
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_add_and_shr_ne_0(i32 %X) {
+  %shr = lshr i32 %X, 4
+  %and = and i32 %shr, 15
+  %add = add i32 %and, -14
+  %tobool = icmp ne i32 %add, 0
+  ret i1 %tobool
+}
-- 
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