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[ARM CodeGen] @llvm.debugtrap call may be removed when restoring callee saved registers 

Summary:
When ARMFrameLowering::emitPopInst generates a "pop" instruction to restore the callee saved registers, it checks if the LR register is among them. If so, the function may decide to remove the basic block's terminator and replace it with a "pop" to the PC register instead of LR.

This leads to a problem when the block's terminator is preceded by a "llvm.debugtrap" call. The MI iterator points to the trap in such a case, which is also a terminator. If the function decides to restore LR to PC, it erroneously removes the trap.

Reviewers: asl, rengolin

Subscribers: aemerson, jfb, rengolin, dschuff, llvm-commits

Differential Revision: http://reviews.llvm.org/D13672

llvm-svn: 251123
This commit is contained in:
Oleg Ranevskyy 2015-10-23 17:17:59 +00:00
parent 5f78c5c293
commit 6389dd9fa2
2 changed files with 22 additions and 1 deletions
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6
llvm/lib/Target/ARM/ARMFrameLowering.cpp
View File

@ -968,12 +968,16 @@ void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
DebugLoc DL;
bool isTailCall = false;
bool isInterrupt = false;
bool isTrap = false;
if (MBB.end() != MI) {
DL = MI->getDebugLoc();
unsigned RetOpcode = MI->getOpcode();
isTailCall = (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri);
isInterrupt =
RetOpcode == ARM::SUBS_PC_LR || RetOpcode == ARM::t2SUBS_PC_LR;
isTrap =
RetOpcode == ARM::TRAP || RetOpcode == ARM::TRAPNaCl ||
RetOpcode == ARM::tTRAP;
}
SmallVector<unsigned, 4> Regs;
@ -990,7 +994,7 @@ void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt &&
STI.hasV5TOps()) {
!isTrap && STI.hasV5TOps()) {
if (MBB.succ_empty()) {
Reg = ARM::PC;
DeleteRet = true;

17
llvm/test/CodeGen/ARM/debugtrap.ll Normal file
View File

@ -0,0 +1,17 @@
; This test ensures the @llvm.debugtrap() call is not removed when generating
; the 'pop' instruction to restore the callee saved registers on ARM.
; RUN: llc < %s -mtriple=armv7 -O0 -filetype=asm | FileCheck %s
declare void @llvm.debugtrap() nounwind
declare void @foo() nounwind
define void @test() nounwind {
entry:
; CHECK: bl foo
; CHECK-NEXT: pop
; CHECK-NEXT: trap
call void @foo()
call void @llvm.debugtrap()
ret void
}