[llvm] r176827 - Don't remove a landing pad if the invoke requires a table entry.

[Duncan Sands]

Hi Bill,

> Don't remove a landing pad if the invoke requires a table entry.
>
> An invoke may require a table entry. For instance, when the function it calls
> is expected to throw.
> <rdar://problem/13360379>

how about doing this at the codegen level instead?  I.e. in codegen, generate an
entry in the exception table when the callee has the UWTable attribute even if
it isn't an invoke.

Ciao, Duncan.

>
> Added:
>      llvm/trunk/test/Transforms/SimplifyCFG/trivial-throw.ll
> Modified:
>      llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>
> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=176827&r1=176826&r2=176827&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Mar 11 15:53:00 2013
> @@ -2789,9 +2789,20 @@ bool SimplifyCFGOpt::SimplifyResume(Resu
>         return false;
>
>     // Turn all invokes that unwind here into calls and delete the basic block.
> +  bool InvokeRequiresTableEntry = false;
> +  bool Changed = false;
>     for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
>       InvokeInst *II = cast<InvokeInst>((*PI++)->getTerminator());
> +
> +    if (II->hasFnAttr(Attribute::UWTable)) {
> +      // Don't remove an `invoke' instruction if the ABI requires an entry into
> +      // the table.
> +      InvokeRequiresTableEntry = true;
> +      continue;
> +    }
> +
>       SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
> +
>       // Insert a call instruction before the invoke.
>       CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II);
>       Call->takeName(II);
> @@ -2811,11 +2822,14 @@ bool SimplifyCFGOpt::SimplifyResume(Resu
>
>       // Finally, delete the invoke instruction!
>       II->eraseFromParent();
> +    Changed = true;
>     }
>
> -  // The landingpad is now unreachable.  Zap it.
> -  BB->eraseFromParent();
> -  return true;
> +  if (!InvokeRequiresTableEntry)
> +    // The landingpad is now unreachable.  Zap it.
> +    BB->eraseFromParent();
> +
> +  return Changed;
>   }
>
>   bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
>
> Added: llvm/trunk/test/Transforms/SimplifyCFG/trivial-throw.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/trivial-throw.ll?rev=176827&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/SimplifyCFG/trivial-throw.ll (added)
> +++ llvm/trunk/test/Transforms/SimplifyCFG/trivial-throw.ll Mon Mar 11 15:53:00 2013
> @@ -0,0 +1,77 @@
> +; RUN: opt -simplifycfg -S < %s | FileCheck %s
> +; <rdar://problem/13360379>
> +
> + at _ZTVN10__cxxabiv117__class_type_infoE = external global i8*
> + at _ZTS13TestException = linkonce_odr constant [16 x i8] c"13TestException\00"
> + at _ZTI13TestException = linkonce_odr unnamed_addr constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([16 x i8]* @_ZTS13TestException, i32 0, i32 0) }
> +
> +define void @throw(i32 %n) #0 {
> +entry:
> +  %exception = call i8* @__cxa_allocate_exception(i64 1) #4
> +  call void @__cxa_throw(i8* %exception, i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*), i8* null) #2
> +  unreachable
> +}
> +
> +define void @func() #0 {
> +entry:
> +; CHECK: func()
> +; CHECK: invoke void @throw
> +; CHECK-NOT: call void @throw
> +  invoke void @throw(i32 42) #0
> +          to label %exit unwind label %lpad
> +
> +lpad:
> +  %tmp0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
> +          cleanup
> +  resume { i8*, i32 } %tmp0
> +
> +exit:
> +  invoke void @abort() #2
> +          to label %invoke.cont unwind label %lpad1
> +
> +invoke.cont:
> +  unreachable
> +
> +lpad1:
> +  %tmp1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
> +          catch i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*)
> +  %tmp2 = extractvalue { i8*, i32 } %tmp1, 1
> +  %tmp3 = call i32 @llvm.eh.typeid.for(i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*)) #4
> +  %matches = icmp eq i32 %tmp2, %tmp3
> +  br i1 %matches, label %catch, label %eh.resume
> +
> +catch:
> +  ret void
> +
> +eh.resume:
> +  resume { i8*, i32 } %tmp1
> +}
> +
> +define linkonce_odr hidden void @__clang_call_terminate(i8*) #1 {
> +  %2 = call i8* @__cxa_begin_catch(i8* %0) #4
> +  call void @_ZSt9terminatev() #5
> +  unreachable
> +}
> +
> +declare void @abort() #2
> +
> +declare i32 @llvm.eh.typeid.for(i8*) #3
> +
> +declare void @__cxa_end_catch()
> +
> +declare i8* @__cxa_allocate_exception(i64)
> +
> +declare i32 @__gxx_personality_v0(...)
> +
> +declare void @__cxa_throw(i8*, i8*, i8*)
> +
> +declare i8* @__cxa_begin_catch(i8*)
> +
> +declare void @_ZSt9terminatev()
> +
> +attributes #0 = { ssp uwtable }
> +attributes #1 = { noinline noreturn nounwind }
> +attributes #2 = { noreturn }
> +attributes #3 = { nounwind readnone }
> +attributes #4 = { nounwind }
> +attributes #5 = { noreturn nounwind }
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>