Clear kill flags in InstrEmitter::EmitSubregNode().

When a local virtual register is made global, make sure to clear any
existing kill flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159461 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 38 insertions, 2 deletions

diff --git a/lib/CodeGen/SelectionDAG/InstrEmitter.cpp b/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
index a57d47ffb3..f154271894 100644
--- a/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
+++ b/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
@@ -470,6 +470,7 @@ void InstrEmitter::EmitSubregNode(SDNode *Node,
       VRBase = MRI->createVirtualRegister(TRC);
       BuildMI(*MBB, InsertPos, Node->getDebugLoc(),
               TII->get(TargetOpcode::COPY), VRBase).addReg(SrcReg);
+      MRI->clearKillFlags(SrcReg);
     } else {
       // VReg may not support a SubIdx sub-register, and we may need to
       // constrain its register class or issue a COPY to a compatible register
diff --git a/test/CodeGen/X86/crash.ll b/test/CodeGen/X86/crash.ll
index cf6e27d159..c71c6ec81d 100644
--- a/test/CodeGen/X86/crash.ll
+++ b/test/CodeGen/X86/crash.ll
@@ -1,5 +1,5 @@
-; RUN: llc -march=x86 %s -o -
-; RUN: llc -march=x86-64 %s -o -
+; RUN: llc -march=x86 < %s -verify-machineinstrs
+; RUN: llc -march=x86-64 < %s -verify-machineinstrs
 
 ; PR6497
 
@@ -391,3 +391,38 @@ if.end:
   %t11 = tail call i64 asm sideeffect "foo", "=*m,=A,{bx},{cx},1,~{memory},~{dirflag},~{fpsr},~{flags}"(i64* %t6, i32 0, i32 0, i64 0) nounwind
   ret void
 }
+
+; Avoid emitting wrong kill flags from InstrEmitter.
+; InstrEmitter::EmitSubregNode() may steal virtual registers from already
+; emitted blocks when isCoalescableExtInstr points out the opportunity.
+; Make sure kill flags are cleared on the newly global virtual register.
+define i64 @ov_read(i8* %vf, i8* nocapture %buffer, i32 %length, i32 %bigendianp, i32 %word, i32 %sgned, i32* %bitstream) nounwind uwtable ssp {
+entry:
+  br i1 undef, label %return, label %while.body.preheader
+
+while.body.preheader:                             ; preds = %entry
+  br i1 undef, label %if.then3, label %if.end7
+
+if.then3:                                         ; preds = %while.body.preheader
+  %0 = load i32* undef, align 4
+  br i1 undef, label %land.lhs.true.i255, label %if.end7
+
+land.lhs.true.i255:                               ; preds = %if.then3
+  br i1 undef, label %if.then.i256, label %if.end7
+
+if.then.i256:                                     ; preds = %land.lhs.true.i255
+  %sub.i = sub i32 0, %0
+  %conv = sext i32 %sub.i to i64
+  br i1 undef, label %if.end7, label %while.end
+
+if.end7:                                          ; preds = %if.then.i256, %land.lhs.true.i255, %if.then3, %while.body.preheader
+  unreachable
+
+while.end:                                        ; preds = %if.then.i256
+  %cmp18 = icmp sgt i32 %sub.i, 0
+  %.conv = select i1 %cmp18, i64 -131, i64 %conv
+  ret i64 %.conv
+
+return:                                           ; preds = %entry
+  ret i64 -131
+}