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Some ARM implementaions, e.g. A-series, does return stack prediction. That is,

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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
This commit is contained in:
Evan Cheng
2012-02-28 06:42:03 +00:00
parent 1f59523521
commit ec52aaa12f
36 changed files with 247 additions and 79 deletions
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6
lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
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@ -2311,8 +2311,10 @@ void DAGTypeLegalizer::ExpandIntRes_XMULO(SDNode *N,
SDValue Func = DAG.getExternalSymbol(TLI.getLibcallName(LC), PtrVT);
std::pair<SDValue, SDValue> CallInfo =
TLI.LowerCallTo(Chain, RetTy, true, false, false, false,
0, TLI.getLibcallCallingConv(LC), false,
true, Func, Args, DAG, dl);
0, TLI.getLibcallCallingConv(LC),
/*isTailCall=*/false,
/*doesNotReturn=*/false, /*isReturnValueUsed=*/true,
Func, Args, DAG, dl);
SplitInteger(CallInfo.first, Lo, Hi);
SDValue Temp2 = DAG.getLoad(PtrVT, dl, CallInfo.second, Temp,