[llvm] r335877 - SelectionDAGBuilder, mach-o: Skip trap after noreturn call (for Mach-O)
Matthias Braun via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 28 10:00:46 PDT 2018
Author: matze
Date: Thu Jun 28 10:00:45 2018
New Revision: 335877
URL: http://llvm.org/viewvc/llvm-project?rev=335877&view=rev
Log:
SelectionDAGBuilder, mach-o: Skip trap after noreturn call (for Mach-O)
Add NoTrapAfterNoreturn target option which skips emission of traps
behind noreturn calls even if TrapUnreachable is enabled.
Enable the feature on Mach-O to save code size; Comments suggest it is
not possible to enable it for the other users of TrapUnreachable.
rdar://41530228
DifferentialRevision: https://reviews.llvm.org/D48674
Added:
llvm/trunk/test/CodeGen/X86/unreachable-trap.ll
Modified:
llvm/trunk/include/llvm/Target/TargetOptions.h
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp
llvm/trunk/lib/Target/X86/X86TargetMachine.cpp
llvm/trunk/test/CodeGen/X86/shadow-stack.ll
Modified: llvm/trunk/include/llvm/Target/TargetOptions.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetOptions.h?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetOptions.h (original)
+++ llvm/trunk/include/llvm/Target/TargetOptions.h Thu Jun 28 10:00:45 2018
@@ -108,6 +108,7 @@ namespace llvm {
DisableIntegratedAS(false), RelaxELFRelocations(false),
FunctionSections(false), DataSections(false),
UniqueSectionNames(true), TrapUnreachable(false),
+ NoTrapAfterNoreturn(false),
EmulatedTLS(false), ExplicitEmulatedTLS(false),
EnableIPRA(false), EmitStackSizeSection(false) {}
@@ -213,6 +214,10 @@ namespace llvm {
/// Emit target-specific trap instruction for 'unreachable' IR instructions.
unsigned TrapUnreachable : 1;
+ /// Do not emit a trap instruction for 'unreachable' IR instructions behind
+ /// noreturn calls, even if TrapUnreachable is true.
+ unsigned NoTrapAfterNoreturn : 1;
+
/// EmulatedTLS - This flag enables emulated TLS model, using emutls
/// function in the runtime library..
unsigned EmulatedTLS : 1;
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu Jun 28 10:00:45 2018
@@ -2625,9 +2625,23 @@ void SelectionDAGBuilder::visitIndirectB
}
void SelectionDAGBuilder::visitUnreachable(const UnreachableInst &I) {
- if (DAG.getTarget().Options.TrapUnreachable)
- DAG.setRoot(
- DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
+ if (!DAG.getTarget().Options.TrapUnreachable)
+ return;
+
+ // We may be able to ignore unreachable behind a noreturn call.
+ if (DAG.getTarget().Options.NoTrapAfterNoreturn) {
+ const BasicBlock &BB = *I.getParent();
+ if (&I != &BB.front()) {
+ BasicBlock::const_iterator PredI =
+ std::prev(BasicBlock::const_iterator(&I));
+ if (const CallInst *Call = dyn_cast<CallInst>(&*PredI)) {
+ if (Call->doesNotReturn())
+ return;
+ }
+ }
+ }
+
+ DAG.setRoot(DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
}
void SelectionDAGBuilder::visitFSub(const User &I) {
Modified: llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp Thu Jun 28 10:00:45 2018
@@ -244,8 +244,10 @@ AArch64TargetMachine::AArch64TargetMachi
TLOF(createTLOF(getTargetTriple())), isLittle(LittleEndian) {
initAsmInfo();
- if (TT.isOSBinFormatMachO())
+ if (TT.isOSBinFormatMachO()) {
this->Options.TrapUnreachable = true;
+ this->Options.NoTrapAfterNoreturn = true;
+ }
// Enable GlobalISel at or below EnableGlobalISelAt0.
if (getOptLevel() <= EnableGlobalISelAtO)
Modified: llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp Thu Jun 28 10:00:45 2018
@@ -239,8 +239,10 @@ ARMBaseTargetMachine::ARMBaseTargetMachi
this->Options.EABIVersion = EABI::EABI5;
}
- if (TT.isOSBinFormatMachO())
+ if (TT.isOSBinFormatMachO()) {
this->Options.TrapUnreachable = true;
+ this->Options.NoTrapAfterNoreturn = true;
+ }
initAsmInfo();
}
Modified: llvm/trunk/lib/Target/X86/X86TargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86TargetMachine.cpp?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86TargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86TargetMachine.cpp Thu Jun 28 10:00:45 2018
@@ -229,8 +229,10 @@ X86TargetMachine::X86TargetMachine(const
// to ever want to mix 32 and 64-bit windows code in a single module
// this should be fine.
if ((TT.isOSWindows() && TT.getArch() == Triple::x86_64) || TT.isPS4() ||
- TT.isOSBinFormatMachO())
+ TT.isOSBinFormatMachO()) {
this->Options.TrapUnreachable = true;
+ this->Options.NoTrapAfterNoreturn = TT.isOSBinFormatMachO();
+ }
initAsmInfo();
}
Modified: llvm/trunk/test/CodeGen/X86/shadow-stack.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/shadow-stack.ll?rev=335877&r1=335876&r2=335877&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/shadow-stack.ll (original)
+++ llvm/trunk/test/CodeGen/X86/shadow-stack.ll Thu Jun 28 10:00:45 2018
@@ -64,7 +64,6 @@ define i32 @bar(i32 %i) local_unnamed_ad
; X86_64-NEXT: movq 8(%rax), %rcx
; X86_64-NEXT: movq 16(%rax), %rsp
; X86_64-NEXT: jmpq *%rcx
-; X86_64-NEXT: ud2
;
; X86-LABEL: bar:
; X86: ## %bb.0: ## %entry
@@ -99,7 +98,6 @@ define i32 @bar(i32 %i) local_unnamed_ad
; X86-NEXT: movl 4(%eax), %ecx
; X86-NEXT: movl 8(%eax), %esp
; X86-NEXT: jmpl *%ecx
-; X86-NEXT: ud2
entry:
%0 = load i8*, i8** @buf, align 8
tail call void @llvm.eh.sjlj.longjmp(i8* %0)
Added: llvm/trunk/test/CodeGen/X86/unreachable-trap.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/unreachable-trap.ll?rev=335877&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/unreachable-trap.ll (added)
+++ llvm/trunk/test/CodeGen/X86/unreachable-trap.ll Thu Jun 28 10:00:45 2018
@@ -0,0 +1,29 @@
+; RUN: llc -o - %s -mtriple=x86_64-windows-msvc | FileCheck %s --check-prefixes=CHECK,TRAP_AFTER_NORETURN
+; RUN: llc -o - %s -mtriple=x86_64-apple-darwin | FileCheck %s --check-prefixes=CHECK,NO_TRAP_AFTER_NORETURN
+
+; CHECK-LABEL: call_exit:
+; CHECK: callq {{_?}}exit
+; TRAP_AFTER_NORETURN: ud2
+; NO_TRAP_AFTER_NORETURN-NOT: ud2
+define i32 @call_exit() noreturn nounwind {
+ tail call void @exit(i32 0)
+ unreachable
+}
+
+; CHECK-LABEL: trap:
+; CHECK: ud2
+; TRAP_AFTER_NORETURN: ud2
+; NO_TRAP_AFTER_NORETURN-NOT: ud2
+define i32 @trap() noreturn nounwind {
+ tail call void @llvm.trap()
+ unreachable
+}
+
+; CHECK-LABEL: unreachable:
+; CHECK: ud2
+define i32 @unreachable() noreturn nounwind {
+ unreachable
+}
+
+declare void @llvm.trap() nounwind noreturn
+declare void @exit(i32 %rc) nounwind noreturn
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