From 21a70bf4a57568d64b535771fd20d25fc0ed9112 Mon Sep 17 00:00:00 2001
From: Cameron Zwarich <zwarich@apple.com>
Date: Fri, 20 May 2011 03:54:04 +0000
Subject: [PATCH] Fix PR9960 by teaching
 SimpleRegisterCoalescing::AdjustCopiesBackFrom() to preserve the phikill
 flag.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131717 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SimpleRegisterCoalescing.cpp      |  5 +++
 .../X86/2011-06-19-QuicksortCoalescerBug.ll   | 31 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 test/CodeGen/X86/2011-06-19-QuicksortCoalescerBug.ll

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 06ed66fee7d..c33ce24c5e8 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -252,7 +252,12 @@ bool SimpleRegisterCoalescing::AdjustCopiesBackFrom(const CoalescerPair &CP,
 
   // Okay, merge "B1" into the same value number as "B0".
   if (BValNo != ValLR->valno) {
+    // If B1 is killed by a PHI, then the merged live range must also be killed
+    // by the same PHI, as B0 and B1 can not overlap.
+    bool HasPHIKill = BValNo->hasPHIKill();
     IntB.MergeValueNumberInto(BValNo, ValLR->valno);
+    if (HasPHIKill)
+      ValLR->valno->setHasPHIKill(true);
   }
   DEBUG({
       dbgs() << "   result = ";
diff --git a/test/CodeGen/X86/2011-06-19-QuicksortCoalescerBug.ll b/test/CodeGen/X86/2011-06-19-QuicksortCoalescerBug.ll
new file mode 100644
index 00000000000..08178a302f2
--- /dev/null
+++ b/test/CodeGen/X86/2011-06-19-QuicksortCoalescerBug.ll
@@ -0,0 +1,31 @@
+; RUN: llc < %s -verify-coalescing
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-macosx10.7.0"
+
+define void @Quicksort(i32* %a, i32 %l, i32 %r) nounwind ssp {
+entry:
+  br label %tailrecurse
+
+tailrecurse:                                      ; preds = %do.cond, %entry
+  %l.tr = phi i32 [ %l, %entry ], [ %i.1, %do.cond ]
+  %r.tr = phi i32 [ %r, %entry ], [ %l.tr, %do.cond ]
+  %idxprom12 = sext i32 %r.tr to i64
+  %arrayidx14 = getelementptr inbounds i32* %a, i64 %idxprom12
+  br label %do.body
+
+do.body:                                          ; preds = %do.cond, %tailrecurse
+  %i.0 = phi i32 [ %l.tr, %tailrecurse ], [ %i.1, %do.cond ]
+  %add7 = add nsw i32 %i.0, 1
+  %cmp = icmp sgt i32 %add7, %r.tr
+  br i1 %cmp, label %do.cond, label %if.then
+
+if.then:                                          ; preds = %do.body
+  store i32 %add7, i32* %arrayidx14, align 4
+  %add16 = add i32 %i.0, 2
+  br label %do.cond
+
+do.cond:                                          ; preds = %do.body, %if.then
+  %i.1 = phi i32 [ %add16, %if.then ], [ %add7, %do.body ]
+  %cmp19 = icmp sgt i32 %i.1, %r.tr
+  br i1 %cmp19, label %tailrecurse, label %do.body
+}
-- 
2.34.1