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[EH] Fix the LSDA that we emit for unknown EH personalities

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We should have a single call site entry with no landing pad. This
indicates that no EH action should be taken and the unwinder should
unwind to the next frame.

We currently don't recognize __gxx_personality_seh0 as a known
personality, so we forcibly emit a table, and that table was wrong. This
was filed as PR33220. Now we emit a correct table for that personality.
The next step is to recognize that we can completely skip the table for
this personality.

llvm-svn: 304363
This commit is contained in:
Reid Kleckner 2017-05-31 22:18:49 +00:00
parent 24768dcf58
commit 0903842407
3 changed files with 48 additions and 5 deletions
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19
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View File

@ -949,6 +949,18 @@ void AsmPrinter::emitFrameAlloc(const MachineInstr &MI) {
MCConstantExpr::create(FrameOffset, OutContext));
}
static bool needFuncLabelsForEHOrDebugInfo(const MachineFunction &MF,
MachineModuleInfo *MMI) {
if (!MF.getLandingPads().empty() || MF.hasEHFunclets() || MMI->hasDebugInfo())
return true;
// We might emit an LSDA anyway if we have an EH personality.
const Constant *PerFn = MF.getFunction()->getPersonalityFn();
if (!PerFn)
return false;
return !isNoOpWithoutInvoke(classifyEHPersonality(PerFn));
}
/// EmitFunctionBody - This method emits the body and trailer for a
/// function.
void AsmPrinter::EmitFunctionBody() {
@ -1076,8 +1088,8 @@ void AsmPrinter::EmitFunctionBody() {
// Emit target-specific gunk after the function body.
EmitFunctionBodyEnd();
if (!MF->getLandingPads().empty() || MMI->hasDebugInfo() ||
MF->hasEHFunclets() || MAI->hasDotTypeDotSizeDirective()) {
if (needFuncLabelsForEHOrDebugInfo(*MF, MMI) ||
MAI->hasDotTypeDotSizeDirective()) {
// Create a symbol for the end of function.
CurrentFnEnd = createTempSymbol("func_end");
OutStreamer->EmitLabel(CurrentFnEnd);
@ -1402,8 +1414,7 @@ void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
CurrentFnBegin = nullptr;
CurExceptionSym = nullptr;
bool NeedsLocalForSize = MAI->needsLocalForSize();
if (!MF.getLandingPads().empty() || MMI->hasDebugInfo() ||
MF.hasEHFunclets() || NeedsLocalForSize) {
if (needFuncLabelsForEHOrDebugInfo(MF, MMI) || NeedsLocalForSize) {
CurrentFnBegin = createTempSymbol("func_begin");
if (NeedsLocalForSize)
CurrentFnSymForSize = CurrentFnBegin;

2
lib/CodeGen/AsmPrinter/EHStreamer.cpp
View File

@ -309,7 +309,7 @@ computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
// If some instruction between the previous try-range and the end of the
// function may throw, create a call-site entry with no landing pad for the
// region following the try-range.
if (SawPotentiallyThrowing && !IsSJLJ && LastLabel != nullptr) {
if (SawPotentiallyThrowing && !IsSJLJ) {
CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
CallSites.push_back(Site);
}

32
test/CodeGen/X86/eh-unknown.ll Normal file
View File

@ -0,0 +1,32 @@
; RUN: llc -mtriple=x86_64-windows-msvc < %s | FileCheck %s
; An unknown personality forces us to emit an Itanium LSDA. Make sure that the
; Itanium call site table actually tells the personality to keep unwinding,
; i.e. we have an entry and it says "has no landing pad".
declare void @throwit()
declare void @__unknown_ehpersonality(...)
define void @use_unknown_ehpersonality()
personality void (...)* @__unknown_ehpersonality {
entry:
call void @throwit()
unreachable
}
; CHECK-LABEL: use_unknown_ehpersonality:
; CHECK: .Lfunc_begin0:
; CHECK: .seh_handler __unknown_ehpersonality, @unwind, @except
; CHECK: callq throwit
; CHECK: .Lfunc_end0:
; CHECK: .seh_handlerdata
; CHECK: .Lexception0:
; CHECK: .byte 255 # @LPStart Encoding = omit
; CHECK: .byte 0 # @TType Encoding = absptr
; CHECK: .asciz "\217\200" # @TType base offset
; CHECK: .byte 3 # Call site Encoding = udata4
; CHECK: .byte 13 # Call site table length
; CHECK: .long .Lfunc_begin0-.Lfunc_begin0 # >> Call Site 1 <<
; CHECK: .long .Lfunc_end0-.Lfunc_begin0 # Call between .Lfunc_begin0 and .Lfunc_end0
; CHECK: .long 0 # has no landing pad
; CHECK: .byte 0 # On action: cleanup