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While we have successfully implemented a funclet-oriented EH scheme on top of LLVM IR, our scheme has some notable deficiencies: - catchendpad and cleanupendpad are necessary in the current design but they are difficult to explain to others, even to seasoned LLVM experts. - catchendpad and cleanupendpad are optimization barriers. They cannot be split and force all potentially throwing call-sites to be invokes. This has a noticable effect on the quality of our code generation. - catchpad, while similar in some aspects to invoke, is fairly awkward. It is unsplittable, starts a funclet, and has control flow to other funclets. - The nesting relationship between funclets is currently a property of control flow edges. Because of this, we are forced to carefully analyze the flow graph to see if there might potentially exist illegal nesting among funclets. While we have logic to clone funclets when they are illegally nested, it would be nicer if we had a representation which forbade them upfront. Let's clean this up a bit by doing the following: - Instead, make catchpad more like cleanuppad and landingpad: no control flow, just a bunch of simple operands; catchpad would be splittable. - Introduce catchswitch, a control flow instruction designed to model the constraints of funclet oriented EH. - Make funclet scoping explicit by having funclet instructions consume the token produced by the funclet which contains them. - Remove catchendpad and cleanupendpad. Their presence can be inferred implicitly using coloring information. N.B. The state numbering code for the CLR has been updated but the veracity of it's output cannot be spoken for. An expert should take a look to make sure the results are reasonable. Reviewers: rnk, JosephTremoulet, andrew.w.kaylor Differential Revision: http://reviews.llvm.org/D15139 llvm-svn: 255422
95 lines
2.6 KiB
C++
95 lines
2.6 KiB
C++
//===- EHPersonalities.h - Compute EH-related information -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_EHPERSONALITIES_H
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#define LLVM_ANALYSIS_EHPERSONALITIES_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/TinyPtrVector.h"
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#include "llvm/Support/ErrorHandling.h"
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namespace llvm {
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class BasicBlock;
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class Function;
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class Value;
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enum class EHPersonality {
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Unknown,
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GNU_Ada,
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GNU_C,
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GNU_CXX,
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GNU_ObjC,
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MSVC_X86SEH,
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MSVC_Win64SEH,
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MSVC_CXX,
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CoreCLR
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};
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/// \brief See if the given exception handling personality function is one
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/// that we understand. If so, return a description of it; otherwise return
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/// Unknown.
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EHPersonality classifyEHPersonality(const Value *Pers);
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/// \brief Returns true if this personality function catches asynchronous
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/// exceptions.
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inline bool isAsynchronousEHPersonality(EHPersonality Pers) {
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// The two SEH personality functions can catch asynch exceptions. We assume
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// unknown personalities don't catch asynch exceptions.
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switch (Pers) {
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case EHPersonality::MSVC_X86SEH:
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case EHPersonality::MSVC_Win64SEH:
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return true;
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default:
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return false;
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}
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llvm_unreachable("invalid enum");
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}
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/// \brief Returns true if this is a personality function that invokes
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/// handler funclets (which must return to it).
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inline bool isFuncletEHPersonality(EHPersonality Pers) {
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switch (Pers) {
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case EHPersonality::MSVC_CXX:
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case EHPersonality::MSVC_X86SEH:
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case EHPersonality::MSVC_Win64SEH:
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case EHPersonality::CoreCLR:
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return true;
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default:
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return false;
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}
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llvm_unreachable("invalid enum");
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}
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/// \brief Return true if this personality may be safely removed if there
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/// are no invoke instructions remaining in the current function.
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inline bool isNoOpWithoutInvoke(EHPersonality Pers) {
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switch (Pers) {
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case EHPersonality::Unknown:
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return false;
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// All known personalities currently have this behavior
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default:
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return true;
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}
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llvm_unreachable("invalid enum");
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}
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bool canSimplifyInvokeNoUnwind(const Function *F);
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typedef TinyPtrVector<BasicBlock *> ColorVector;
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/// \brief If an EH funclet personality is in use (see isFuncletEHPersonality),
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/// this will recompute which blocks are in which funclet. It is possible that
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/// some blocks are in multiple funclets. Consider this analysis to be
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/// expensive.
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DenseMap<BasicBlock *, ColorVector> colorEHFunclets(Function &F);
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} // end namespace llvm
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#endif
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