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[X86] Fix a crash in FEntryInserter Pass.

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Summary:
FEntryInserter pass unconditionally derefs the first Instruction
in the first Basic Block. The pass crashes when the first
BasicBlock is empty. Fix the crash by not dereferencing the basic
Block iterator. This fixes an issue observed when building Linux kernel
4.4 with clang.

Fixes PR33971.

Reviewers: hfinkel, niravd, dblaikie

Reviewed By: niravd

Subscribers: davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D35979

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309694 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manoj Gupta 2017-08-01 15:39:12 +00:00
parent 2a519cbde9
commit f6fecfacea
2 changed files with 16 additions and 4 deletions
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4
lib/CodeGen/FEntryInserter.cpp
View File

@ -41,10 +41,8 @@ bool FEntryInserter::runOnMachineFunction(MachineFunction &MF) {
return false;
auto &FirstMBB = *MF.begin();
auto &FirstMI = *FirstMBB.begin();
auto *TII = MF.getSubtarget().getInstrInfo();
BuildMI(FirstMBB, FirstMI, FirstMI.getDebugLoc(),
BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(),
TII->get(TargetOpcode::FENTRY_CALL));
return true;
}

16
test/CodeGen/X86/fentry-insertion.ll
View File

@ -12,5 +12,19 @@ entry:
; CHECK: retq
}
attributes #0 = { "fentry-call"="true" }
define void @test2() #1 {
entry:
br label %bb1
bb1:
call void @address_taken(i64 ptrtoint (i8* blockaddress(@test2, %bb1) to i64), i32 512)
ret void
; CHECK-LABEL: @test2
; CHECK: callq __fentry__
; CHECK-NOT: mcount
; CHECK: retq
}
declare void @address_taken(i64, i32) local_unnamed_addr
attributes #0 = { "fentry-call"="true" }
attributes #1 = { inlinehint minsize noredzone nounwind optsize sspstrong "fentry-call"="true" }