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the processor keeps a return addresses stack (RAS) which stores the address and the instruction execution state of the instruction after a function-call type branch instruction. Calling a "noreturn" function with normal call instructions (e.g. bl) can corrupt RAS and causes 100% return misprediction so LLVM should use a unconditional branch instead. i.e. mov lr, pc b _foo The "mov lr, pc" is issued in order to get proper backtrace. rdar://8979299 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151623 91177308-0d34-0410-b5e6-96231b3b80d8
31 lines
598 B
LLVM
31 lines
598 B
LLVM
; RUN: llc < %s -mtriple=armv7-apple-ios -mcpu=cortex-a8 | FileCheck %s -check-prefix=ARM
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; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 | FileCheck %s -check-prefix=T2
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; rdar://8979299
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define void @t1() noreturn nounwind ssp {
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entry:
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; ARM: t1:
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; ARM: mov lr, pc
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; ARM: b _bar
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; T2: t1:
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; T2: blx _bar
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tail call void @bar() noreturn nounwind
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unreachable
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}
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define void @t2() noreturn nounwind ssp {
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entry:
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; ARM: t2:
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; ARM: mov lr, pc
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; ARM: b _t1
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; T2: t2:
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; T2: mov lr, pc
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; T2: b.w _t1
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tail call void @t1() noreturn nounwind
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unreachable
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}
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declare void @bar() noreturn
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