From 02e08d5b4d9d368418debaf9ff2b3f07425ee0b6 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames@gmail.com>
Date: Thu, 2 Feb 2012 05:37:34 +0000
Subject: [PATCH] PR11868. The previous loop in LiveIntervals::join would
 sometimes fall over if more than two adjacent ranges needed to be merged. The
 new version should be able to handle an arbitrary sequence of adjancent
 ranges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149588 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LiveInterval.cpp                  | 23 ++++++++--------
 .../Generic/2012-02-01-CoalescerBug.ll        | 26 +++++++++++++++++++
 2 files changed, 38 insertions(+), 11 deletions(-)
 create mode 100644 test/CodeGen/Generic/2012-02-01-CoalescerBug.ll

diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index a85639f9c19..0dbaaf804b6 100644
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -389,29 +389,30 @@ void LiveInterval::join(LiveInterval &Other,
   // now.
   if (MustMapCurValNos) {
     // Map the first live range.
+
     iterator OutIt = begin();
     OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
-    ++OutIt;
-    for (iterator I = OutIt, E = end(); I != E; ++I) {
-      OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
+    for (iterator I = next(OutIt), E = end(); I != E; ++I) {
+      VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
+      assert(nextValNo != 0 && "Huh?");
 
       // If this live range has the same value # as its immediate predecessor,
       // and if they are neighbors, remove one LiveRange.  This happens when we
-      // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
-      if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
-        (OutIt-1)->end = OutIt->end;
+      // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
+      if (OutIt->valno == nextValNo && OutIt->end == I->start) {
+        OutIt->end = I->end;
       } else {
-        if (I != OutIt) {
+        // Didn't merge. Move OutIt to the next interval,
+        ++OutIt;
+        OutIt->valno = nextValNo;
+        if (OutIt != I) {
           OutIt->start = I->start;
           OutIt->end = I->end;
         }
-
-        // Didn't merge, on to the next one.
-        ++OutIt;
       }
     }
-
     // If we merge some live ranges, chop off the end.
+    ++OutIt;
     ranges.erase(OutIt, end());
   }
 
diff --git a/test/CodeGen/Generic/2012-02-01-CoalescerBug.ll b/test/CodeGen/Generic/2012-02-01-CoalescerBug.ll
new file mode 100644
index 00000000000..6c7aaad7c69
--- /dev/null
+++ b/test/CodeGen/Generic/2012-02-01-CoalescerBug.ll
@@ -0,0 +1,26 @@
+; RUN: llc -verify-coalescing < %s
+; PR11868
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:64:128-a0:0:64-n32-S64"
+target triple = "armv7-none-linux-gnueabi"
+
+%0 = type { <4 x float> }
+%1 = type { <4 x float> }
+
+@foo = external global %0, align 16
+
+define arm_aapcs_vfpcc void @bar(float, i1 zeroext, i1 zeroext) nounwind {
+  %4 = load <4 x float>* getelementptr inbounds (%0* @foo, i32 0, i32 0), align 16
+  %5 = extractelement <4 x float> %4, i32 0
+  %6 = extractelement <4 x float> %4, i32 1
+  %7 = extractelement <4 x float> %4, i32 2
+  %8 = insertelement <4 x float> undef, float %5, i32 0
+  %9 = insertelement <4 x float> %8, float %6, i32 1
+  %10 = insertelement <4 x float> %9, float %7, i32 2
+  %11 = insertelement <4 x float> %10, float 0.000000e+00, i32 3
+  store <4 x float> %11, <4 x float>* undef, align 16 
+  call arm_aapcs_vfpcc  void @baz(%1* undef, float 0.000000e+00) nounwind
+  ret void
+}
+
+declare arm_aapcs_vfpcc void @baz(%1*, float)