From 2f88006cedd06b8e2be1e9d282ba7e3bf88f57ca 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

llvm-svn: 342176
---
 llvm/lib/CodeGen/MachineInstr.cpp                  |  6 ++++--
 .../CodeGen/X86/ms-inline-asm-redundant-clobber.ll | 24 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 37e23ae..2f32359 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/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/llvm/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll b/llvm/test/CodeGen/X86/ms-inline-asm-redundant-clobber.ll
new file mode 100644
index 0000000..7b525e0
--- /dev/null
+++ b/llvm/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
+}
-- 
2.7.4