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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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10
lib/Target/XCore/XCoreISelLowering.cpp
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@ -487,8 +487,8 @@ LowerLOAD(SDValue Op, SelectionDAG &DAG) const {
std::pair<SDValue, SDValue> CallResult =
LowerCallTo(Chain, IntPtrTy, false, false,
false, false, 0, CallingConv::C, false,
/*isReturnValueUsed=*/true,
false, false, 0, CallingConv::C, /*isTailCall=*/false,
/*doesNotRet=*/false, /*isReturnValueUsed=*/true,
DAG.getExternalSymbol("__misaligned_load", getPointerTy()),
Args, DAG, DL);
@ -549,8 +549,8 @@ LowerSTORE(SDValue Op, SelectionDAG &DAG) const
std::pair<SDValue, SDValue> CallResult =
LowerCallTo(Chain, Type::getVoidTy(*DAG.getContext()), false, false,
false, false, 0, CallingConv::C, false,
/*isReturnValueUsed=*/true,
false, false, 0, CallingConv::C, /*isTailCall=*/false,
/*doesNotRet=*/false, /*isReturnValueUsed=*/true,
DAG.getExternalSymbol("__misaligned_store", getPointerTy()),
Args, DAG, dl);
@ -875,7 +875,7 @@ LowerINIT_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const {
SDValue
XCoreTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
CallingConv::ID CallConv, bool isVarArg,
bool &isTailCall,
bool doesNotRet, bool &isTailCall,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals,
const SmallVectorImpl<ISD::InputArg> &Ins,