From 0af20d847ac89f797d613a8a4fc3e7127ccb0b36 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Sat, 13 Mar 2010 02:20:29 +0000
Subject: [PATCH] Fix a typo in ValueTracking that's causing instcombine to
 delete needed shift instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98416 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ValueTracking.cpp           |  2 +-
 test/Transforms/InstCombine/shift-sra.ll | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 92cbb7c95c0..5ae72f7aba9 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -779,7 +779,7 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD,
     for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
       if (Tmp == 1) return Tmp;
       Tmp = std::min(Tmp,
-                     ComputeNumSignBits(PN->getIncomingValue(1), TD, Depth+1));
+                     ComputeNumSignBits(PN->getIncomingValue(i), TD, Depth+1));
     }
     return Tmp;
   }
diff --git a/test/Transforms/InstCombine/shift-sra.ll b/test/Transforms/InstCombine/shift-sra.ll
index 58f322635c2..a578bbe4d4f 100644
--- a/test/Transforms/InstCombine/shift-sra.ll
+++ b/test/Transforms/InstCombine/shift-sra.ll
@@ -56,3 +56,23 @@ C:
 ; CHECK: %P = phi i64
 ; CHECK-NEXT: ret i64 %P
 }
+
+; rdar://7732987
+define i32 @test5(i32 %Y) {
+  br i1 undef, label %A, label %C
+A:
+  br i1 undef, label %B, label %D
+B:
+  br label %D
+C:
+  br i1 undef, label %D, label %E
+D:
+  %P = phi i32 [0, %A], [0, %B], [%Y, %C] 
+  %S = ashr i32 %P, 16
+  ret i32 %S
+; CHECK: @test5
+; CHECK: %P = phi i32
+; CHECK-NEXT: ashr i32 %P, 16
+E:
+  ret i32 0
+}