From ee5f4639a8f93d80faef1f864022bec2fde35997 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@intel.com>
Date: Thu, 13 Sep 2018 20:51:27 +0000
Subject: [PATCH] [MachineInstr] In addRegisterKilled and addRegisterDead,
 don't remove operands from inline assembly instructions if they have an
 associated flag operand.

INLINEASM instructions use extra operands to carry flags. If a register operand is removed without removing the flag operand, then the flags will no longer make sense.

This patch fixes this by preventing the removal when a flag operand is present.

The included test case was generated by MS inline assembly. Longer term maybe we should fix the inline assembly parsing to not generate redundant operands.

Differential Revision: https://reviews.llvm.org/D51829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342176 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineInstr.cpp                  |  6 +++--
 .../X86/ms-inline-asm-redundant-clobber.ll    | 24 +++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll

diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index 37e23aee000..2f323597741 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1766,7 +1766,8 @@ bool MachineInstr::addRegisterKilled(unsigned IncomingReg,
   // Trim unneeded kill operands.
   while (!DeadOps.empty()) {
     unsigned OpIdx = DeadOps.back();
-    if (getOperand(OpIdx).isImplicit())
+    if (getOperand(OpIdx).isImplicit() &&
+        (!isInlineAsm() || findInlineAsmFlagIdx(OpIdx) < 0))
       RemoveOperand(OpIdx);
     else
       getOperand(OpIdx).setIsKill(false);
@@ -1830,7 +1831,8 @@ bool MachineInstr::addRegisterDead(unsigned Reg,
   // Trim unneeded dead operands.
   while (!DeadOps.empty()) {
     unsigned OpIdx = DeadOps.back();
-    if (getOperand(OpIdx).isImplicit())
+    if (getOperand(OpIdx).isImplicit() &&
+        (!isInlineAsm() || findInlineAsmFlagIdx(OpIdx) < 0))
       RemoveOperand(OpIdx);
     else
       getOperand(OpIdx).setIsDead(false);
diff --git a/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll b/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll
new file mode 100644
index 00000000000..7b525e09851
--- /dev/null
+++ b/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll
@@ -0,0 +1,24 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+; This used to crash due to Live Variable analysis removing the redundant eax
+; and edx clobbers, but not removing the inline asm flag operands that proceed
+; them.
+
+@test_mem = dso_local global [16 x i8] c"UUUUUUUUUUUUUUUU", align 16
+
+; Function Attrs: nounwind uwtable
+define dso_local void @foo() local_unnamed_addr {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    #APP
+; CHECK:         clc
+; CHECK-NEXT:    cmpxchg8b {{.*}}(%rip)
+; CHECK-NEXT:    cmpxchg16b {{.*}}(%rip)
+; CHECK-NEXT:    clc
+; CHECK:         #NO_APP
+; CHECK-NEXT:    retq
+entry:
+  tail call void asm sideeffect inteldialect "clc\0A\09cmpxchg8b $0\0A\09cmpxchg16b $1\0A\09clc", "=*m,=*m,~{eax},~{edx},~{flags},~{rax},~{rdx},~{dirflag},~{fpsr},~{flags}"([16 x i8]* nonnull @test_mem, [16 x i8]* nonnull @test_mem) #1
+  ret void
+}