[NFC ]Add a helper function isTailCall for getting libcall in SelectionDAG #155256
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@llvm/pr-subscribers-llvm-selectiondag Author: zhijian lin (diggerlin) ChangesBased on comment of #153600 (comment), Add a helper function isTailCall for getting libcall in SelectionDAG. Full diff: https://github.com/llvm/llvm-project/pull/155256.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 4b7fc45908119..cc9cd50e2c6f9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -9012,6 +9012,14 @@ static void checkAddrSpaceIsValidForLibcall(const TargetLowering *TLI,
}
}
+static bool isTailCall(const CallInst *CI, const SelectionDAG *SelDAG,
+ bool IsLowerToLibCall) {
+ bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI);
+ return CI && CI->isTailCall() &&
+ isInTailCallPosition(*CI, SelDAG->getTarget(),
+ ReturnsFirstArg && IsLowerToLibCall);
+}
+
std::pair<SDValue, SDValue>
SelectionDAG::getMemcmp(SDValue Chain, const SDLoc &dl, SDValue Mem0,
SDValue Mem1, SDValue Size, const CallInst *CI) {
@@ -9033,10 +9041,7 @@ SelectionDAG::getMemcmp(SDValue Chain, const SDLoc &dl, SDValue Mem0,
GetEntry(getDataLayout().getIntPtrType(*getContext()), Size)};
TargetLowering::CallLoweringInfo CLI(*this);
- bool IsTailCall = false;
- bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI);
- IsTailCall = CI && CI->isTailCall() &&
- isInTailCallPosition(*CI, getTarget(), ReturnsFirstArg);
+ bool IsTailCall = isTailCall(CI, this, /*LowerToLibCall*/ true);
CLI.setDebugLoc(dl)
.setChain(Chain)
@@ -9117,10 +9122,7 @@ SDValue SelectionDAG::getMemcpy(
IsTailCall = *OverrideTailCall;
} else {
bool LowersToMemcpy = StringRef(MemCpyName) == StringRef("memcpy");
- bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI);
- IsTailCall = CI && CI->isTailCall() &&
- isInTailCallPosition(*CI, getTarget(),
- ReturnsFirstArg && LowersToMemcpy);
+ IsTailCall = isTailCall(CI, this, LowersToMemcpy);
}
CLI.setDebugLoc(dl)
@@ -9234,10 +9236,7 @@ SDValue SelectionDAG::getMemmove(SDValue Chain, const SDLoc &dl, SDValue Dst,
} else {
bool LowersToMemmove =
TLI->getLibcallName(RTLIB::MEMMOVE) == StringRef("memmove");
- bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI);
- IsTailCall = CI && CI->isTailCall() &&
- isInTailCallPosition(*CI, getTarget(),
- ReturnsFirstArg && LowersToMemmove);
+ IsTailCall = isTailCall(CI, this, LowersToMemmove);
}
CLI.setDebugLoc(dl)
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| bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI); | ||
| return CI && CI->isTailCall() && | ||
| isInTailCallPosition(*CI, SelDAG->getTarget(), | ||
| ReturnsFirstArg && IsLowerToLibCall); |
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This requires explanation. The arguments for the calls that are generated are not changed by this condition. Why would ReturnsFirstArg be different?
| @@ -9012,6 +9012,14 @@ static void checkAddrSpaceIsValidForLibcall(const TargetLowering *TLI, | |||
| } | |||
| } | |||
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| static bool isTailCall(const CallInst *CI, const SelectionDAG *SelDAG, | |||
| bool IsLowerToLibCall) { | |||
| bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI); | |||
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This will always return false for a null CallInst, but you have 2 null checks on it. Tail call should be possible even without the CallInst? I thought we handled tail call of new calls already?
At least turn into early exit or pull the null checks into the caller
| @@ -9012,6 +9012,14 @@ static void checkAddrSpaceIsValidForLibcall(const TargetLowering *TLI, | |||
| } | |||
| } | |||
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| static bool isTailCall(const CallInst *CI, const SelectionDAG *SelDAG, | |||
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Name isn't quite right. This is more like an extended version of isInTailCallPosition.
| @@ -9012,6 +9012,14 @@ static void checkAddrSpaceIsValidForLibcall(const TargetLowering *TLI, | |||
| } | |||
| } | |||
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| static bool isTailCall(const CallInst *CI, const SelectionDAG *SelDAG, | |||
| bool IsLowerToLibCall) { | |||
| bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI); | |||
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On second thought, why do you need the IR analysis for funcReturnsFirstArgOfCall? You know that based on the properties of the known libcall without looking at the IR
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It's about what the caller returns, not what the library call returns, for tail call deliberations.
Based on comment of #153600 (comment), Add a helper function isTailCall for getting libcall in SelectionDAG.