From 3b156699381e266b8c620056c139b876524df2eb Mon Sep 17 00:00:00 2001
From: Andrea Di Biagio <Andrea_DiBiagio@sn.scee.net>
Date: Thu, 30 Apr 2015 21:03:29 +0000
Subject: [PATCH] Fix for PR23103. Correctly propagate the 'IsUndef' flag to
 the register operands of a commuted instruction.

Revision 220239 exposed a latent bug in method
'TargetInstrInfo::commuteInstruction'. When commuting the operands of a machine
instruction, method 'commuteInstruction' didn't correctly propagate the
'IsUndef' flag to the register operands of the new (commuted) instruction.

Before this patch, the following instruction:
  %vreg4<def> = VADDSDrr  %vreg14, %vreg5<undef>; FR64:%vreg4,%vreg14,%vreg5

was wrongly converted by method 'commuteInstruction' into:
  %vreg4<def> = VADDSDrr  %vreg5, %vreg14<undef>; FR64:%vreg4,%vreg5,%vreg14

The correct instruction should have been:
  %vreg4<def> = VADDSDrr  %vreg5<undef>, %vreg14; FR64:%vreg4,%vreg5,%vreg14

This patch fixes the problem in method 'TargetInstrInfo::commuteInstruction'.
When swapping the operands of a machine instruction, we now make sure that
'IsUndef' flags are correctly set.
Added test case 'pr23103.ll'.

Differential Revision: http://reviews.llvm.org/D9406


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236258 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/TargetInstrInfo.cpp |  4 ++++
 test/CodeGen/X86/pr23103.ll     | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 test/CodeGen/X86/pr23103.ll

diff --git a/lib/CodeGen/TargetInstrInfo.cpp b/lib/CodeGen/TargetInstrInfo.cpp
index 38725b53b37..165df0696ef 100644
--- a/lib/CodeGen/TargetInstrInfo.cpp
+++ b/lib/CodeGen/TargetInstrInfo.cpp
@@ -142,6 +142,8 @@ MachineInstr *TargetInstrInfo::commuteInstruction(MachineInstr *MI,
   unsigned SubReg2 = MI->getOperand(Idx2).getSubReg();
   bool Reg1IsKill = MI->getOperand(Idx1).isKill();
   bool Reg2IsKill = MI->getOperand(Idx2).isKill();
+  bool Reg1IsUndef = MI->getOperand(Idx1).isUndef();
+  bool Reg2IsUndef = MI->getOperand(Idx2).isUndef();
   // If destination is tied to either of the commuted source register, then
   // it must be updated.
   if (HasDef && Reg0 == Reg1 &&
@@ -172,6 +174,8 @@ MachineInstr *TargetInstrInfo::commuteInstruction(MachineInstr *MI,
   MI->getOperand(Idx1).setSubReg(SubReg2);
   MI->getOperand(Idx2).setIsKill(Reg1IsKill);
   MI->getOperand(Idx1).setIsKill(Reg2IsKill);
+  MI->getOperand(Idx2).setIsUndef(Reg1IsUndef);
+  MI->getOperand(Idx1).setIsUndef(Reg2IsUndef);
   return MI;
 }
 
diff --git a/test/CodeGen/X86/pr23103.ll b/test/CodeGen/X86/pr23103.ll
new file mode 100644
index 00000000000..e0508effac0
--- /dev/null
+++ b/test/CodeGen/X86/pr23103.ll
@@ -0,0 +1,21 @@
+; RUN: llc -verify-machineinstrs -mtriple=x86_64-unknown-unknown -mcpu=generic -mattr=+avx < %s | FileCheck %s
+
+; When commuting a VADDSDrr instruction, verify that the 'IsUndef' flag is
+; correctly propagated to the operands of the resulting instruction.
+; Test for PR23103;
+
+declare zeroext i1 @foo(<1 x double>)
+
+define <1 x double> @pr23103(<1 x double>* align 8 %Vp) {
+; CHECK-LABEL: pr23103:
+; CHECK:         vmovsd (%rdi), %xmm0
+; CHECK-NEXT:    vmovsd %xmm0, {{.*}}(%rsp) {{.*#+}} 8-byte Spill
+; CHECK-NEXT:    callq foo
+; CHECK-NEXT:    vaddsd {{.*}}(%rsp), %xmm0, %xmm0 {{.*#+}} 8-byte Folded Reload
+; CHECK:         retq
+entry:
+  %V = load <1 x double>, <1 x double>* %Vp, align 8
+  %call = call zeroext i1 @foo(<1 x double> %V)
+  %fadd = fadd <1 x double> %V, undef
+  ret <1 x double> %fadd
+}