From c41acffe2297585ad56aa772de75e82c132070bb Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Fri, 9 Jan 2015 03:01:31 +0000
Subject: [PATCH] RegisterCoalescer: Fix removeCopyByCommutingDef with subreg
 liveness

The code that eliminated additional coalescable copies in
removeCopyByCommutingDef() used MergeValueNumberInto() which internally
may merge A into B or B into A. In this case A and B had different Def
points, so we have to reset ValNo.Def to the intended one after merging.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225503 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/RegisterCoalescer.cpp           |  4 +-
 test/CodeGen/X86/coalesce_commute_subreg.ll | 51 +++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/coalesce_commute_subreg.ll

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 127ab45372b..bce469c2322 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -751,7 +751,9 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
       if (!SubDVNI)
         continue;
       VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
-      S.MergeValueNumberInto(SubBValNo, SubDVNI);
+      assert(SubBValNo->def == CopyIdx);
+      VNInfo *Merged = S.MergeValueNumberInto(SubBValNo, SubDVNI);
+      Merged->def = CopyIdx;
     }
 
     ErasedInstrs.insert(UseMI);
diff --git a/test/CodeGen/X86/coalesce_commute_subreg.ll b/test/CodeGen/X86/coalesce_commute_subreg.ll
new file mode 100644
index 00000000000..8d0a20cfebb
--- /dev/null
+++ b/test/CodeGen/X86/coalesce_commute_subreg.ll
@@ -0,0 +1,51 @@
+; RUN: llc -mtriple="x86_64-apple-darwin" -o - -verify-machineinstrs %s
+
+define void @make_wanted() #0 {
+entry:
+  br i1 undef, label %for.end20, label %for.cond1.preheader.lr.ph
+
+for.cond1.preheader.lr.ph:
+  br label %for.body3
+
+for.body3:
+  %cmp20.i = icmp eq i32 undef, 0
+  %.col.057 = select i1 %cmp20.i, i32 0, i32 undef
+  br i1 undef, label %while.cond.i, label %for.body5.lr.ph.i
+
+for.body5.lr.ph.i:
+  %0 = sext i32 %.col.057 to i64
+  %1 = sub i32 0, %.col.057
+  %2 = zext i32 %1 to i64
+  %3 = add nuw nsw i64 %2, 1
+  %n.vec110 = and i64 %3, 8589934588
+  %end.idx.rnd.down111 = add nsw i64 %n.vec110, %0
+  br i1 undef, label %middle.block105, label %vector.ph103
+
+vector.ph103:
+  br i1 undef, label %middle.block105, label %vector.body104
+
+vector.body104:
+  %4 = icmp eq i64 undef, %end.idx.rnd.down111
+  br i1 %4, label %middle.block105, label %vector.body104
+
+middle.block105:
+  %resume.val114 = phi i64 [ %0, %for.body5.lr.ph.i ], [ %end.idx.rnd.down111, %vector.body104 ], [ %end.idx.rnd.down111, %vector.ph103 ]
+  %cmp.n116 = icmp eq i64 undef, %resume.val114
+  br i1 %cmp.n116, label %while.cond.i, label %for.body5.i.preheader
+
+for.body5.i.preheader:
+  %lcmp.or182 = or i1 undef, undef
+  br i1 %lcmp.or182, label %for.body5.i.prol, label %while.cond.i
+
+for.body5.i.prol:
+  br i1 undef, label %for.body5.i.prol, label %while.cond.i
+
+while.cond.i:
+  br i1 undef, label %while.cond.i, label %if.then
+
+if.then:
+  br label %for.body3
+
+for.end20:
+  ret void
+}