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[X86] nocf_check: disable tail call #131487

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Merged
merged 2 commits into from
Mar 16, 2025
Merged

[X86] nocf_check: disable tail call #131487

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5d110b3
[𝘀𝗽𝗿] initial version
MaskRay Mar 16, 2025
27631f1
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MaskRay Mar 16, 2025
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12 changes: 9 additions & 3 deletions llvm/lib/Target/X86/X86ISelLoweringCall.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2034,11 +2034,17 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
X86MachineFunctionInfo *X86Info = MF.getInfo<X86MachineFunctionInfo>();
bool HasNCSR = (CB && isa<CallInst>(CB) &&
CB->hasFnAttr("no_caller_saved_registers"));
bool HasNoCfCheck = (CB && CB->doesNoCfCheck());
bool IsIndirectCall = (CB && isa<CallInst>(CB) && CB->isIndirectCall());
bool IsCFICall = IsIndirectCall && CLI.CFIType;
const Module *M = MF.getFunction().getParent();
Metadata *IsCFProtectionSupported = M->getModuleFlag("cf-protection-branch");

// If the indirect call target has the nocf_check attribute, the call needs
// the NOTRACK prefix. For simplicity just disable tail calls as there are
// so many variants.
bool IsNoTrackIndirectCall = IsIndirectCall && CB->doesNoCfCheck() &&
M->getModuleFlag("cf-protection-branch");
if (IsNoTrackIndirectCall)
isTailCall = false;

MachineFunction::CallSiteInfo CSInfo;
if (CallConv == CallingConv::X86_INTR)
Expand Down Expand Up @@ -2549,7 +2555,7 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,

// Returns a chain & a glue for retval copy to use.
SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
if (HasNoCfCheck && IsCFProtectionSupported && IsIndirectCall) {
if (IsNoTrackIndirectCall) {
Chain = DAG.getNode(X86ISD::NT_CALL, dl, NodeTys, Ops);
} else if (CLI.CB && objcarc::hasAttachedCallOpBundle(CLI.CB)) {
// Calls with a "clang.arc.attachedcall" bundle are special. They should be
Expand Down
23 changes: 23 additions & 0 deletions llvm/test/CodeGen/X86/nocf_check.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,29 @@ entry:
ret void
}

;; NOTRACK tail call is not implemented, so nocf_check just disables tail call.
define void @NoCfCheckTail(ptr %p) #1 {
; CHECK-LABEL: NoCfCheckTail:
; CHECK: notrack callq *%rax
%f = load ptr, ptr %p, align 4
tail call void %f() #2
ret void
}

define void @NoCfCheckTailCond(ptr %f, i1 %x) #1 {
; CHECK-LABEL: NoCfCheckTailCond:
; CHECK: notrack callq *%rdi
; CHECK: notrack callq *%rdi
entry:
br i1 %x, label %bb1, label %bb2
bb1:
tail call void %f() #2
ret void
bb2:
tail call void %f() #2
ret void
}

attributes #0 = { nocf_check noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nocf_check }
Expand Down
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