[llvm] 662024d - [X86] Don't copy kill flag when expanding LCMPXCHG16B_SAVE_RBX

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2020-10-09T11:55:24-07:00
New Revision: 662024df331bd1f1a206678435e51232683e3cf6

URL: https://github.com/llvm/llvm-project/commit/662024df331bd1f1a206678435e51232683e3cf6
DIFF: https://github.com/llvm/llvm-project/commit/662024df331bd1f1a206678435e51232683e3cf6.diff

LOG: [X86] Don't copy kill flag when expanding LCMPXCHG16B_SAVE_RBX

The expansion code creates a copy to RBX before the real LCMPXCHG16B.
It's possible this copy uses a register that is also used by the
real LCMPXCHG16B. If we set the kill flag on the use in the copy,
then we'll fail the machine verifier on the use on the LCMPXCHG16B.

Differential Revision: https://reviews.llvm.org/D89151

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86ExpandPseudo.cpp
    llvm/test/CodeGen/X86/pr42064.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86ExpandPseudo.cpp b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
index d9c0964e9ed8..b1d15225eaaf 100644
--- a/llvm/lib/Target/X86/X86ExpandPseudo.cpp
+++ b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
@@ -346,7 +346,9 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
 
     // Copy the input argument of the pseudo into the argument of the
     // actual instruction.
-    TII->copyPhysReg(MBB, MBBI, DL, X86::RBX, InArg.getReg(), InArg.isKill());
+    // NOTE: We don't copy the kill flag since the input might be the same reg
+    // as one of the other operands of LCMPXCHG16B.
+    TII->copyPhysReg(MBB, MBBI, DL, X86::RBX, InArg.getReg(), false);
     // Create the actual instruction.
     MachineInstr *NewInstr = BuildMI(MBB, MBBI, DL, TII->get(X86::LCMPXCHG16B));
     // Copy the operands related to the address.

diff  --git a/llvm/test/CodeGen/X86/pr42064.ll b/llvm/test/CodeGen/X86/pr42064.ll
index 6269a59ff055..089895da18a1 100644
--- a/llvm/test/CodeGen/X86/pr42064.ll
+++ b/llvm/test/CodeGen/X86/pr42064.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=x86_64-pc-windows-msvc19.11.0 -mattr=+avx,+cx16 | FileCheck %s
+; RUN: llc < %s -verify-machineinstrs -mtriple=x86_64-pc-windows-msvc19.11.0 -mattr=+avx,+cx16 | FileCheck %s
 
 %struct.TestStruct = type { %union.Int128 }
 %union.Int128 = type { i128 }