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Assure calling "cld" instruction in prologue of X86 interrupt handler function.

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Differential Revision: http://reviews.llvm.org/D18725


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269413 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Amjad Aboud 2016-05-13 12:46:57 +00:00
parent ce7190c29e
commit c0cc51c8de
2 changed files with 29 additions and 0 deletions
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12
lib/Target/X86/X86FrameLowering.cpp
View File

@ -1381,6 +1381,18 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
if (PushedRegs)
emitCalleeSavedFrameMoves(MBB, MBBI, DL);
}
// X86 Interrupt handling function cannot assume anything about the direction
// flag (DF in EFLAGS register). Clear this flag by creating "cld" instruction
// in each prologue of interrupt handler function.
//
// FIXME: Create "cld" instruction only in these cases:
// 1. The interrupt handling function uses any of the "rep" instructions.
// 2. Interrupt handling function calls another function.
//
if (Fn->getCallingConv() == CallingConv::X86_INTR)
BuildMI(MBB, MBBI, DL, TII.get(X86::CLD))
.setMIFlag(MachineInstr::FrameSetup);
}
bool X86FrameLowering::canUseLEAForSPInEpilogue(

17
test/CodeGen/X86/x86-interrupt_cld.ll Normal file
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@ -0,0 +1,17 @@
; RUN: llc -mtriple=x86_64-unknown-unknown < %s | FileCheck %s
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Checks that interrupt handler code calls cld before calling an external
;; function.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; CHECK: cld
; CHECK: call
define x86_intrcc void @foo(i8* %frame) {
call void @bar()
ret void
}
declare void @bar()