[llvm] 0ffe83f - [SelectionDAG] Not issue TRAP node if naked function (#132147)
via llvm-commits
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Thu Mar 20 18:18:06 PDT 2025
Author: yonghong-song
Date: 2025-03-20T18:18:03-07:00
New Revision: 0ffe83feaca02cf1c7a25c559c72cc16813a2f86
URL: https://github.com/llvm/llvm-project/commit/0ffe83feaca02cf1c7a25c559c72cc16813a2f86
DIFF: https://github.com/llvm/llvm-project/commit/0ffe83feaca02cf1c7a25c559c72cc16813a2f86.diff
LOG: [SelectionDAG] Not issue TRAP node if naked function (#132147)
In [1], Nikita Popov suggested that during lowering 'unreachable' insn
should not generate extra code for naked functions, and this applies to
all architectures. Note that for naked functions, 'unreachable' insn is
necessary in IR since the basic block needs a terminator to end.
This patch checked whether a function is naked function or not. If it is
a naked function, 'unreachable' insn will not generate ISD::TRAP.
[1] https://github.com/llvm/llvm-project/pull/131731
Co-authored-by: Yonghong Song <yonghong.song at linux.dev>
Added:
llvm/test/CodeGen/X86/naked-fn-with-unreachable-trap.ll
Modified:
llvm/include/llvm/IR/Instructions.h
llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/lib/IR/Instructions.cpp
llvm/test/CodeGen/WebAssembly/naked-fn-with-frame-pointer.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index a1f964352207f..9a4fb2985264b 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -4497,6 +4497,9 @@ class UnreachableInst : public Instruction {
return isa<Instruction>(V) && classof(cast<Instruction>(V));
}
+ // Whether to do target lowering in SelectionDAG.
+ bool shouldLowerToTrap(bool TrapUnreachable, bool NoTrapAfterNoreturn) const;
+
private:
BasicBlock *getSuccessor(unsigned idx) const {
llvm_unreachable("UnreachableInst has no successors!");
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 6014f57d439f0..f8afb42bf5535 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -3143,21 +3143,12 @@ bool IRTranslator::translateVAArg(const User &U, MachineIRBuilder &MIRBuilder) {
return true;
}
-bool IRTranslator::translateUnreachable(const User &U, MachineIRBuilder &MIRBuilder) {
- if (!MF->getTarget().Options.TrapUnreachable)
- return true;
-
+bool IRTranslator::translateUnreachable(const User &U,
+ MachineIRBuilder &MIRBuilder) {
auto &UI = cast<UnreachableInst>(U);
-
- // We may be able to ignore unreachable behind a noreturn call.
- if (const CallInst *Call = dyn_cast_or_null<CallInst>(UI.getPrevNode());
- Call && Call->doesNotReturn()) {
- if (MF->getTarget().Options.NoTrapAfterNoreturn)
- return true;
- // Do not emit an additional trap instruction.
- if (Call->isNonContinuableTrap())
- return true;
- }
+ if (!UI.shouldLowerToTrap(MF->getTarget().Options.TrapUnreachable,
+ MF->getTarget().Options.NoTrapAfterNoreturn))
+ return true;
MIRBuilder.buildTrap();
return true;
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 33dd039c4ab2a..fbc0264961bc7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1854,17 +1854,12 @@ bool FastISel::selectOperator(const User *I, unsigned Opcode) {
}
case Instruction::Unreachable: {
- if (TM.Options.TrapUnreachable) {
- if (TM.Options.NoTrapAfterNoreturn) {
- const auto *Call =
- dyn_cast_or_null<CallInst>(cast<Instruction>(I)->getPrevNode());
- if (Call && Call->doesNotReturn())
- return true;
- }
+ auto UI = cast<UnreachableInst>(I);
+ if (!UI->shouldLowerToTrap(TM.Options.TrapUnreachable,
+ TM.Options.NoTrapAfterNoreturn))
+ return true;
- return fastEmit_(MVT::Other, MVT::Other, ISD::TRAP) != 0;
- }
- return true;
+ return fastEmit_(MVT::Other, MVT::Other, ISD::TRAP) != 0;
}
case Instruction::Alloca:
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 1d0a3f8294546..e3c34382d6354 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3501,19 +3501,10 @@ void SelectionDAGBuilder::visitIndirectBr(const IndirectBrInst &I) {
}
void SelectionDAGBuilder::visitUnreachable(const UnreachableInst &I) {
- if (!DAG.getTarget().Options.TrapUnreachable)
+ if (!I.shouldLowerToTrap(DAG.getTarget().Options.TrapUnreachable,
+ DAG.getTarget().Options.NoTrapAfterNoreturn))
return;
- // We may be able to ignore unreachable behind a noreturn call.
- if (const CallInst *Call = dyn_cast_or_null<CallInst>(I.getPrevNode());
- Call && Call->doesNotReturn()) {
- if (DAG.getTarget().Options.NoTrapAfterNoreturn)
- return;
- // Do not emit an additional trap instruction.
- if (Call->isNonContinuableTrap())
- return;
- }
-
DAG.setRoot(DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
}
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index d2cf0ae2c1778..18109bf107858 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -4529,6 +4529,27 @@ UnreachableInst *UnreachableInst::cloneImpl() const {
return new UnreachableInst(Context);
}
+bool UnreachableInst::shouldLowerToTrap(bool TrapUnreachable,
+ bool NoTrapAfterNoreturn) const {
+ if (!TrapUnreachable)
+ return false;
+
+ // We may be able to ignore unreachable behind a noreturn call.
+ if (const CallInst *Call = dyn_cast_or_null<CallInst>(getPrevNode());
+ Call && Call->doesNotReturn()) {
+ if (NoTrapAfterNoreturn)
+ return false;
+ // Do not emit an additional trap instruction.
+ if (Call->isNonContinuableTrap())
+ return false;
+ }
+
+ if (getFunction()->hasFnAttribute(Attribute::Naked))
+ return false;
+
+ return true;
+}
+
FreezeInst *FreezeInst::cloneImpl() const {
return new FreezeInst(getOperand(0));
}
diff --git a/llvm/test/CodeGen/WebAssembly/naked-fn-with-frame-pointer.ll b/llvm/test/CodeGen/WebAssembly/naked-fn-with-frame-pointer.ll
index fcd42e8cbfb9f..d50cf0b201229 100644
--- a/llvm/test/CodeGen/WebAssembly/naked-fn-with-frame-pointer.ll
+++ b/llvm/test/CodeGen/WebAssembly/naked-fn-with-frame-pointer.ll
@@ -9,13 +9,11 @@ define dso_local void @naked() naked "frame-pointer"="all" {
; CHECK-32: .functype naked () -> ()
; CHECK-32-NEXT: # %bb.0:
; CHECK-32-NEXT: call main
-; CHECK-32-NEXT: unreachable
;
; CHECK-64-LABEL: naked:
; CHECK-64: .functype naked () -> ()
; CHECK-64-NEXT: # %bb.0:
; CHECK-64-NEXT: call main
-; CHECK-64-NEXT: unreachable
call void @main()
unreachable
}
diff --git a/llvm/test/CodeGen/X86/naked-fn-with-unreachable-trap.ll b/llvm/test/CodeGen/X86/naked-fn-with-unreachable-trap.ll
new file mode 100644
index 0000000000000..94274fcb1c160
--- /dev/null
+++ b/llvm/test/CodeGen/X86/naked-fn-with-unreachable-trap.ll
@@ -0,0 +1,11 @@
+; RUN: llc -o - %s -mtriple=x86_64-linux-gnu -trap-unreachable | FileCheck %s
+; RUN: llc -o - %s -mtriple=x86_64-linux-gnu -trap-unreachable -fast-isel | FileCheck %s
+
+define dso_local void @foo() #0 {
+entry:
+ tail call void asm sideeffect "movl 3,%eax", "~{dirflag},~{fpsr},~{flags}"()
+ unreachable
+}
+; CHECK-NOT: ud2
+
+attributes #0 = { naked }
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