Validated by nightly-test runs on x86 and x86-64 darwin, including after
self-host. Hopefully these results hold up on different platforms.
I tried to keep the GNU ObjC runtime happy, but it's hard for me to test.
Reimplement how clang generates IR for exceptions. Instead of creating new
invoke destinations which sequentially chain to the previous destination,
push a more semantic representation of *why* we need the cleanup/catch/filter
behavior, then collect that information into a single landing pad upon request.
Also reorganizes how normal cleanups (i.e. cleanups triggered by non-exceptional
control flow) are generated, since it's actually fairly closely tied in with
the former. Remove the need to track which cleanup scope a block is associated
with.
Document a lot of previously poorly-understood (by me, at least) behavior.
The new framework implements the Horrible Hack (tm), which requires every
landing pad to have a catch-all so that inlining will work. Clang no longer
requires the Horrible Hack just to make exceptions flow correctly within
a function, however. The HH is an unfortunate requirement of LLVM's EH IR.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107631 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGException.h b/lib/CodeGen/CGException.h
new file mode 100644
index 0000000..8755dca
--- /dev/null
+++ b/lib/CodeGen/CGException.h
@@ -0,0 +1,342 @@
+//===-- CGException.h - Classes for exceptions IR generation ----*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// These classes support the generation of LLVM IR for exceptions in
+// C++ and Objective C.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CLANG_CODEGEN_CGEXCEPTION_H
+#define CLANG_CODEGEN_CGEXCEPTION_H
+
+/// EHScopeStack is defined in CodeGenFunction.h, but its
+/// implementation is in this file and in CGException.cpp.
+#include "CodeGenFunction.h"
+
+namespace llvm {
+ class Value;
+ class BasicBlock;
+}
+
+namespace clang {
+namespace CodeGen {
+
+/// A protected scope for zero-cost EH handling.
+class EHScope {
+ llvm::BasicBlock *CachedLandingPad;
+
+ unsigned K : 2;
+
+protected:
+ enum { BitsRemaining = 30 };
+
+public:
+ enum Kind { Cleanup, Catch, Terminate, Filter };
+
+ EHScope(Kind K) : CachedLandingPad(0), K(K) {}
+
+ Kind getKind() const { return static_cast<Kind>(K); }
+
+ llvm::BasicBlock *getCachedLandingPad() const {
+ return CachedLandingPad;
+ }
+
+ void setCachedLandingPad(llvm::BasicBlock *Block) {
+ CachedLandingPad = Block;
+ }
+};
+
+/// A scope which attempts to handle some, possibly all, types of
+/// exceptions.
+///
+/// Objective C @finally blocks are represented using a cleanup scope
+/// after the catch scope.
+class EHCatchScope : public EHScope {
+ unsigned NumHandlers : BitsRemaining;
+
+ // In effect, we have a flexible array member
+ // Handler Handlers[0];
+ // But that's only standard in C99, not C++, so we have to do
+ // annoying pointer arithmetic instead.
+
+public:
+ struct Handler {
+ /// A type info value, or null (C++ null, not an LLVM null pointer)
+ /// for a catch-all.
+ llvm::Value *Type;
+
+ /// The catch handler for this type.
+ llvm::BasicBlock *Block;
+
+ static Handler make(llvm::Value *Type, llvm::BasicBlock *Block) {
+ Handler Temp;
+ Temp.Type = Type;
+ Temp.Block = Block;
+ return Temp;
+ }
+ };
+
+private:
+ Handler *getHandlers() {
+ return reinterpret_cast<Handler*>(this+1);
+ }
+
+ const Handler *getHandlers() const {
+ return reinterpret_cast<const Handler*>(this+1);
+ }
+
+public:
+ static size_t getSizeForNumHandlers(unsigned N) {
+ return sizeof(EHCatchScope) + N * sizeof(Handler);
+ }
+
+ EHCatchScope(unsigned NumHandlers)
+ : EHScope(Catch), NumHandlers(NumHandlers) {
+ }
+
+ unsigned getNumHandlers() const {
+ return NumHandlers;
+ }
+
+ void setCatchAllHandler(unsigned I, llvm::BasicBlock *Block) {
+ setHandler(I, /*catchall*/ 0, Block);
+ }
+
+ void setHandler(unsigned I, llvm::Value *Type, llvm::BasicBlock *Block) {
+ assert(I < getNumHandlers());
+ getHandlers()[I] = Handler::make(Type, Block);
+ }
+
+ const Handler &getHandler(unsigned I) const {
+ assert(I < getNumHandlers());
+ return getHandlers()[I];
+ }
+
+ typedef const Handler *iterator;
+ iterator begin() const { return getHandlers(); }
+ iterator end() const { return getHandlers() + getNumHandlers(); }
+
+ static bool classof(const EHScope *Scope) {
+ return Scope->getKind() == Catch;
+ }
+};
+
+/// A scope which needs to execute some code if we try to unwind ---
+/// either normally, via the EH mechanism, or both --- through it.
+class EHCleanupScope : public EHScope {
+ /// The number of fixups required by enclosing scopes (not including
+ /// this one). If this is the top cleanup scope, all the fixups
+ /// from this index onwards belong to this scope.
+ unsigned FixupDepth : BitsRemaining;
+
+ /// The nearest normal cleanup scope enclosing this one.
+ EHScopeStack::stable_iterator EnclosingNormal;
+
+ /// The nearest EH cleanup scope enclosing this one.
+ EHScopeStack::stable_iterator EnclosingEH;
+
+ llvm::BasicBlock *NormalEntry;
+ llvm::BasicBlock *NormalExit;
+ llvm::BasicBlock *EHEntry;
+ llvm::BasicBlock *EHExit;
+
+public:
+ static size_t getSize() { return sizeof(EHCleanupScope); }
+
+ EHCleanupScope(unsigned FixupDepth,
+ EHScopeStack::stable_iterator EnclosingNormal,
+ EHScopeStack::stable_iterator EnclosingEH,
+ llvm::BasicBlock *NormalEntry, llvm::BasicBlock *NormalExit,
+ llvm::BasicBlock *EHEntry, llvm::BasicBlock *EHExit)
+ : EHScope(Cleanup), FixupDepth(FixupDepth),
+ EnclosingNormal(EnclosingNormal), EnclosingEH(EnclosingEH),
+ NormalEntry(NormalEntry), NormalExit(NormalExit),
+ EHEntry(EHEntry), EHExit(EHExit) {
+ assert((NormalEntry != 0) == (NormalExit != 0));
+ assert((EHEntry != 0) == (EHExit != 0));
+ }
+
+ bool isNormalCleanup() const { return NormalEntry != 0; }
+ bool isEHCleanup() const { return EHEntry != 0; }
+
+ llvm::BasicBlock *getNormalEntry() const { return NormalEntry; }
+ llvm::BasicBlock *getNormalExit() const { return NormalExit; }
+ llvm::BasicBlock *getEHEntry() const { return EHEntry; }
+ llvm::BasicBlock *getEHExit() const { return EHExit; }
+ unsigned getFixupDepth() const { return FixupDepth; }
+ EHScopeStack::stable_iterator getEnclosingNormalCleanup() const {
+ return EnclosingNormal;
+ }
+ EHScopeStack::stable_iterator getEnclosingEHCleanup() const {
+ return EnclosingEH;
+ }
+
+ static bool classof(const EHScope *Scope) {
+ return Scope->getKind() == Cleanup;
+ }
+};
+
+/// An exceptions scope which filters exceptions thrown through it.
+/// Only exceptions matching the filter types will be permitted to be
+/// thrown.
+///
+/// This is used to implement C++ exception specifications.
+class EHFilterScope : public EHScope {
+ unsigned NumFilters : BitsRemaining;
+
+ // Essentially ends in a flexible array member:
+ // llvm::Value *FilterTypes[0];
+
+ llvm::Value **getFilters() {
+ return reinterpret_cast<llvm::Value**>(this+1);
+ }
+
+ llvm::Value * const *getFilters() const {
+ return reinterpret_cast<llvm::Value* const *>(this+1);
+ }
+
+public:
+ EHFilterScope(unsigned NumFilters) :
+ EHScope(Filter), NumFilters(NumFilters) {}
+
+ static size_t getSizeForNumFilters(unsigned NumFilters) {
+ return sizeof(EHFilterScope) + NumFilters * sizeof(llvm::Value*);
+ }
+
+ unsigned getNumFilters() const { return NumFilters; }
+
+ void setFilter(unsigned I, llvm::Value *FilterValue) {
+ assert(I < getNumFilters());
+ getFilters()[I] = FilterValue;
+ }
+
+ llvm::Value *getFilter(unsigned I) const {
+ assert(I < getNumFilters());
+ return getFilters()[I];
+ }
+
+ static bool classof(const EHScope *Scope) {
+ return Scope->getKind() == Filter;
+ }
+};
+
+/// An exceptions scope which calls std::terminate if any exception
+/// reaches it.
+class EHTerminateScope : public EHScope {
+public:
+ EHTerminateScope() : EHScope(Terminate) {}
+ static size_t getSize() { return sizeof(EHTerminateScope); }
+
+ static bool classof(const EHScope *Scope) {
+ return Scope->getKind() == Terminate;
+ }
+};
+
+/// A non-stable pointer into the scope stack.
+class EHScopeStack::iterator {
+ char *Ptr;
+
+ friend class EHScopeStack;
+ explicit iterator(char *Ptr) : Ptr(Ptr) {}
+
+public:
+ iterator() : Ptr(0) {}
+
+ EHScope *get() const {
+ return reinterpret_cast<EHScope*>(Ptr);
+ }
+
+ EHScope *operator->() const { return get(); }
+ EHScope &operator*() const { return *get(); }
+
+ iterator &operator++() {
+ switch (get()->getKind()) {
+ case EHScope::Catch:
+ Ptr += EHCatchScope::getSizeForNumHandlers(
+ static_cast<const EHCatchScope*>(get())->getNumHandlers());
+ break;
+
+ case EHScope::Filter:
+ Ptr += EHFilterScope::getSizeForNumFilters(
+ static_cast<const EHFilterScope*>(get())->getNumFilters());
+ break;
+
+ case EHScope::Cleanup:
+ Ptr += EHCleanupScope::getSize();
+ break;
+
+ case EHScope::Terminate:
+ Ptr += EHTerminateScope::getSize();
+ break;
+ }
+
+ return *this;
+ }
+
+ iterator next() {
+ iterator copy = *this;
+ ++copy;
+ return copy;
+ }
+
+ iterator operator++(int) {
+ iterator copy = *this;
+ operator++();
+ return copy;
+ }
+
+ bool operator==(iterator other) const { return Ptr == other.Ptr; }
+ bool operator!=(iterator other) const { return Ptr != other.Ptr; }
+};
+
+inline EHScopeStack::iterator EHScopeStack::begin() const {
+ return iterator(StartOfData);
+}
+
+inline EHScopeStack::iterator EHScopeStack::end() const {
+ return iterator(EndOfBuffer);
+}
+
+inline void EHScopeStack::popCatch() {
+ assert(!empty() && "popping exception stack when not empty");
+
+ assert(isa<EHCatchScope>(*begin()));
+ StartOfData += EHCatchScope::getSizeForNumHandlers(
+ cast<EHCatchScope>(*begin()).getNumHandlers());
+
+ assert(CatchDepth > 0 && "mismatched catch/terminate push/pop");
+ CatchDepth--;
+}
+
+inline void EHScopeStack::popTerminate() {
+ assert(!empty() && "popping exception stack when not empty");
+
+ assert(isa<EHTerminateScope>(*begin()));
+ StartOfData += EHTerminateScope::getSize();
+
+ assert(CatchDepth > 0 && "mismatched catch/terminate push/pop");
+ CatchDepth--;
+}
+
+inline EHScopeStack::iterator EHScopeStack::find(stable_iterator sp) const {
+ assert(sp.isValid() && "finding invalid savepoint");
+ assert(sp.Size <= stable_begin().Size && "finding savepoint after pop");
+ return iterator(EndOfBuffer - sp.Size);
+}
+
+inline EHScopeStack::stable_iterator
+EHScopeStack::stabilize(iterator ir) const {
+ assert(StartOfData <= ir.Ptr && ir.Ptr <= EndOfBuffer);
+ return stable_iterator(EndOfBuffer - ir.Ptr);
+}
+
+}
+}
+
+#endif