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[X86] Don't add implicit REP prefix to VIA PadLock xstore

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Commit 8fa3e8fa1492 added an implicit REP prefix to all VIA PadLock
instructions, but GNU as doesn't add one to xstore, only all the others.
This resulted in a kernel panic regression in FreeBSD upon updating to
LLVM 11 (https://bugs.freebsd.org/259218) which includes the commit in
question. This partially reverts that commit.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D112355
This commit is contained in:
Jessica Clarke 2021-10-23 01:56:05 +01:00
parent b432583d28
commit 2d8c18fbbd
2 changed files with 5 additions and 2 deletions
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2
llvm/lib/Target/X86/X86InstrSystem.td
View File

@ -584,7 +584,7 @@ def XRSTORS64 : RI<0xC7, MRM3m, (outs), (ins opaquemem:$dst),
//===----------------------------------------------------------------------===//
// VIA PadLock crypto instructions
let Defs = [RAX, RDI], Uses = [RDX, RDI], SchedRW = [WriteSystem] in
def XSTORE : I<0xa7, MRM_C0, (outs), (ins), "xstore", []>, TB, REP;
def XSTORE : I<0xa7, MRM_C0, (outs), (ins), "xstore", []>, TB;
def : InstAlias<"xstorerng", (XSTORE)>;

5
llvm/test/MC/X86/padlock.s
View File

@ -1,8 +1,11 @@
// RUN: llvm-mc -triple i386-unknown-unknown --show-encoding %s | FileCheck %s
/// Check xstore does not get an implicit REP prefix but all other PadLock
/// instructions do.
xstore
// CHECK: xstore
// CHECK: encoding: [0xf3,0x0f,0xa7,0xc0]
// CHECK: encoding: [0x0f,0xa7,0xc0]
xcryptecb
// CHECK: xcryptecb
// CHECK: encoding: [0xf3,0x0f,0xa7,0xc8]