Some ARM implementaions, e.g. A-series, does return stack prediction. That is,
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
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index aa51ced..ab84706 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1286,7 +1286,7 @@
SDValue
ARMTargetLowering::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,
@@ -1582,12 +1582,20 @@
if (Subtarget->isThumb()) {
if ((!isDirect || isARMFunc) && !Subtarget->hasV5TOps())
CallOpc = ARMISD::CALL_NOLINK;
+ else if (doesNotRet && !isARMFunc &&
+ Subtarget->hasRAS() && !Subtarget->isThumb1Only())
+ // "mov lr, pc; b _foo" to avoid confusing the RSP
+ CallOpc = ARMISD::CALL_NOLINK;
else
CallOpc = isARMFunc ? ARMISD::CALL : ARMISD::tCALL;
} else {
- CallOpc = (isDirect || Subtarget->hasV5TOps())
- ? (isLocalARMFunc ? ARMISD::CALL_PRED : ARMISD::CALL)
- : ARMISD::CALL_NOLINK;
+ if (!isDirect && !Subtarget->hasV5TOps()) {
+ CallOpc = ARMISD::CALL_NOLINK;
+ } else if (doesNotRet && Subtarget->hasRAS())
+ // "mov lr, pc; b _foo" to avoid confusing the RSP
+ CallOpc = ARMISD::CALL_NOLINK;
+ else
+ CallOpc = isLocalARMFunc ? ARMISD::CALL_PRED : ARMISD::CALL;
}
std::vector<SDValue> Ops;
@@ -2080,7 +2088,8 @@
std::pair<SDValue, SDValue> CallResult =
LowerCallTo(Chain, (Type *) Type::getInt32Ty(*DAG.getContext()),
false, false, false, false,
- 0, CallingConv::C, false, /*isReturnValueUsed=*/true,
+ 0, CallingConv::C, /*isTailCall=*/false,
+ /*doesNotRet=*/false, /*isReturnValueUsed=*/true,
DAG.getExternalSymbol("__tls_get_addr", PtrVT), Args, DAG, dl);
return CallResult.first;
}