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X86FrameLowering: Check subregs when deciding prolog kill flags 

llvm-svn: 274057
This commit is contained in:
Matthias Braun 2016-06-28 20:31:56 +00:00
parent 91c66275e9
commit 0b9a07883d
2 changed files with 36 additions and 3 deletions
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18
llvm/lib/Target/X86/X86FrameLowering.cpp
View File

@ -1893,17 +1893,29 @@ bool X86FrameLowering::spillCalleeSavedRegisters(
if (!X86::GR64RegClass.contains(Reg) && !X86::GR32RegClass.contains(Reg))
continue;
bool isLiveIn = MF.getRegInfo().isLiveIn(Reg);
const MachineRegisterInfo &MRI = MF.getRegInfo();
bool isLiveIn = MRI.isLiveIn(Reg);
if (!isLiveIn)
MBB.addLiveIn(Reg);
// Decide whether we can add a kill flag to the use.
bool CanKill = !isLiveIn;
// Check if any subregister is live-in
if (CanKill) {
for (MCRegAliasIterator AReg(Reg, TRI, false); AReg.isValid(); ++AReg) {
if (MRI.isLiveIn(*AReg)) {
CanKill = false;
break;
}
}
}
// Do not set a kill flag on values that are also marked as live-in. This
// happens with the @llvm-returnaddress intrinsic and with arguments
// passed in callee saved registers.
// Omitting the kill flags is conservatively correct even if the live-in
// is not used after all.
bool isKill = !isLiveIn;
BuildMI(MBB, MI, DL, TII.get(Opc)).addReg(Reg, getKillRegState(isKill))
BuildMI(MBB, MI, DL, TII.get(Opc)).addReg(Reg, getKillRegState(CanKill))
.setMIFlag(MachineInstr::FrameSetup);
}

21
llvm/test/CodeGen/X86/no-prolog-kill.ll Normal file
View File

@ -0,0 +1,21 @@
; RUN: llc -verify-machineinstrs -o - %s | FileCheck %s
target triple = "x86_64--"
; This function gets a AL live-in and at same time saves+restores RAX. We must
; not add a kill flag to the "PUSHQ %rax" or the machine verifier will complain.
; CHECK-LABEL: test:
; CHECK: pushq %rax
; CHECK: testb %al, %al
; CHECK: je .LBB
define void @test(i64 %a, i8* %b, ...) {
entry:
%bar = alloca i8
call void @llvm.va_start(i8* %bar)
call void @llvm.eh.unwind.init()
call void @llvm.eh.return.i64(i64 %a, i8* %b)
unreachable
}
declare void @llvm.eh.return.i64(i64, i8*)
declare void @llvm.eh.unwind.init()
declare void @llvm.va_start(i8*)