From cc846016bfa5bba6dad85cf48fc58ab16e56a9e7 Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Sun, 30 Jun 2013 13:47:43 +0000
Subject: [PATCH] ConstantFold: Check that truncating the other side is safe
 under a sext when trying to remove a sext from a compare.

Fixes PR16462.

llvm-svn: 185284
---
 llvm/lib/IR/ConstantFold.cpp                  |  4 ++--
 .../InstCombine/2010-03-03-ExtElim.ll         | 20 ++++++++++++++++---
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index bf93d4f95663..da9762fa627d 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -1857,9 +1857,9 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
         if (CE1Inverse == CE1Op0) {
           // Check whether we can safely truncate the right hand side.
           Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
-          if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) {
+          if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
+                                    C2->getType()) == C2)
             return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
-          }
         }
       }
     }
diff --git a/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
index bb3159e1e6fa..4b1930584c56 100644
--- a/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
+++ b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
@@ -1,5 +1,4 @@
 ; RUN: opt -instcombine -S < %s | FileCheck %s
-; PR6486
 
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
 target triple = "i386-unknown-linux-gnu"
@@ -7,8 +6,8 @@ target triple = "i386-unknown-linux-gnu"
 @g_92 = common global [2 x i32*] zeroinitializer, align 4 ; <[2 x i32*]*> [#uses=1]
 @g_177 = constant i32** bitcast (i8* getelementptr (i8* bitcast ([2 x i32*]* @g_92 to i8*), i64 4) to i32**), align 4 ; <i32***> [#uses=1]
 
-define i1 @test() nounwind {
-; CHECK: @test
+define i1 @PR6486() nounwind {
+; CHECK: @PR6486
   %tmp = load i32*** @g_177                       ; <i32**> [#uses=1]
   %cmp = icmp ne i32** null, %tmp                 ; <i1> [#uses=1]
   %conv = zext i1 %cmp to i32                     ; <i32> [#uses=1]
@@ -16,3 +15,18 @@ define i1 @test() nounwind {
   ret i1 %cmp1
 ; CHECK: ret i1 true
 }
+
+@d = common global i32 0, align 4
+@a = common global [1 x i32] zeroinitializer, align 4
+
+define i1 @PR16462_1() nounwind {
+; CHECK: @PR16462_1
+  ret i1 icmp sgt (i32 sext (i16 trunc (i32 select (i1 icmp eq (i32* getelementptr inbounds ([1 x i32]* @a, i32 0, i32 0), i32* @d), i32 0, i32 1) to i16) to i32), i32 65535)
+; CHECK: ret i1 icmp sgt (i32 sext (i16 trunc (i32 select (i1 icmp eq (i32* getelementptr inbounds ([1 x i32]* @a, i32 0, i32 0), i32* @d), i32 0, i32 1) to i16) to i32), i32 65535)
+}
+
+define i1 @PR16462_2() nounwind {
+; CHECK: @PR16462_2
+  ret i1 icmp sgt (i32 sext (i16 trunc (i32 select (i1 icmp eq (i32* getelementptr inbounds ([1 x i32]* @a, i32 0, i32 0), i32* @d), i32 0, i32 1) to i16) to i32), i32 42)
+; CHECK: ret i1 icmp sgt (i16 trunc (i32 select (i1 icmp eq (i32* getelementptr inbounds ([1 x i32]* @a, i32 0, i32 0), i32* @d), i32 0, i32 1) to i16), i16 42)
+}
-- 
2.34.1