[llvm-branch-commits] [cfe-branch] r83179 - /cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp
Bill Wendling
isanbard at gmail.com
Wed Sep 30 15:27:08 PDT 2009
Author: void
Date: Wed Sep 30 17:27:07 2009
New Revision: 83179
URL: http://llvm.org/viewvc/llvm-project?rev=83179&view=rev
Log:
This changes the Objective-C exception handling code gen. Instead of relying
upon exception handling tables, we write the exception handling explicitly in
the code. Conceptually, there is only one catch block: a catch-all. It then
checks the type thrown against the types that can be caught by all of the catch
blocks, if any. If one of them can catch, control is passed to it. If none
catch, the exception is rethrown. The @finally block is worked in there in the
usual fashion (*HAND WAVING* *HAND WAVING*).
What I wrote about the exception tables above isn't 100% correct. There will
still be exception handling tables. However, they will only have catch-all
entries in them.
Modified:
cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp
Modified: cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp?rev=83179&r1=83178&r2=83179&view=diff
==============================================================================
--- cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp (original)
+++ cfe/branches/eh-experiment/lib/CodeGen/CGObjCMac.cpp Wed Sep 30 17:27:07 2009
@@ -5420,109 +5420,117 @@
: cast<ObjCAtSynchronizedStmt>(S).getSynchBody());
CGF.EmitBranchThroughCleanup(FinallyEnd);
- // Emit the exception handler.
+ // Emit the exception handler. Organize the exception handling in this way:
+ //
+ // - Create a catch-all landing pad (try.handler), which creates the
+ // exception object and retrieves the type thrown.
+ // - Compare the type thrown to the type that a catch block can catch.
+ // - If they are equal, then execute the associated catch block.
+ // - If they aren't equal, check to see if the next catch block can catch
+ // it.
+ // - If we hit a catch-all block, then execute the associated catch block.
+ // - If none of the blocks can catch the exception, then call `unwind'.
+ //
+ // try.handler:
+ // .----------------------------------------------.
+ // | %eh_exc = eh.exception() |
+ // | %eh_sel = eh.landingpad(%eh_ptr, %per, null) |
+ // | %eh_tid1 = eh.typeid.for(...) |---> catch_body_1
+ // | %a = icmp ne %eh_sel, %eh_tid1 |
+ // | br %a, %next_tid_1, %catch_body_1 |
+ // `----------------------------------------------'
+ // |
+ // next_tid_1: v
+ // .----------------------------------------------.
+ // | %eh_tid2 = eh.typeid.for(...) |
+ // | %b = icmp ne %eh_sel, %eh_tid2 |---> catch_body_2
+ // | br %b, %next_tid_2, %catch_body_2 |
+ // `----------------------------------------------'
+ // |
+ // v
+ // ...
+ // |
+ // last: v
+ // .--------.
+ // | unwind | ; Only if no catch-all is present.
+ // `--------'
CGF.EmitBlock(TryHandler);
llvm::Value *llvm_eh_exception =
CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_exception);
- llvm::Value *llvm_eh_selector_i64 =
- CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_selector_i64);
+ llvm::Value *llvm_eh_landingpad_i64 =
+ CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_landingpad_i64);
llvm::Value *llvm_eh_typeid_for_i64 =
CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for_i64);
- llvm::Value *Exc = CGF.Builder.CreateCall(llvm_eh_exception, "exc");
+ llvm::Value *Exc = CGF.Builder.CreateCall(llvm_eh_exception, "eh_exc");
llvm::Value *RethrowPtr = CGF.CreateTempAlloca(Exc->getType(), "_rethrow");
+ // The landing pad is always a catch-all. We determine the appropriate catch
+ // block to call by explicitly checking the thrown type.
llvm::SmallVector<llvm::Value*, 8> SelectorArgs;
SelectorArgs.push_back(Exc);
SelectorArgs.push_back(ObjCTypes.getEHPersonalityPtr());
+ SelectorArgs.push_back(llvm::Constant::getNullValue(ObjCTypes.Int8PtrTy));
+
+ llvm::Value *Selector =
+ CGF.Builder.CreateCall(llvm_eh_landingpad_i64,
+ SelectorArgs.begin(), SelectorArgs.end(),
+ "eh_sel");
- // Construct the lists of (type, catch body) to handle.
- llvm::SmallVector<std::pair<const ParmVarDecl*, const Stmt*>, 8> Handlers;
- bool HasCatchAll = false;
if (isTry) {
- if (const ObjCAtCatchStmt* CatchStmt =
- cast<ObjCAtTryStmt>(S).getCatchStmts()) {
- for (; CatchStmt; CatchStmt = CatchStmt->getNextCatchStmt()) {
- const ParmVarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
- Handlers.push_back(std::make_pair(CatchDecl, CatchStmt->getCatchBody()));
-
- // catch(...) always matches.
- if (!CatchDecl) {
- // Use i8* null here to signal this is a catch all, not a cleanup.
- llvm::Value *Null = llvm::Constant::getNullValue(ObjCTypes.Int8PtrTy);
- SelectorArgs.push_back(Null);
- HasCatchAll = true;
- break;
- }
+ bool HasCatchAll = false;
+ const ObjCAtCatchStmt *CatchStmt = cast<ObjCAtTryStmt>(S).getCatchStmts();
+
+ for (; CatchStmt; CatchStmt = CatchStmt->getNextCatchStmt()) {
+ const ParmVarDecl *CatchParam = CatchStmt->getCatchParamDecl();
+ const Stmt *CatchBody = CatchStmt->getCatchBody();
+ llvm::BasicBlock *CatchNextChk = 0;
+
+ if (CatchParam) {
+ // This is *not* a catch-all block.
+ llvm::Value *ExcTyId = 0;
- if (CatchDecl->getType()->isObjCIdType() ||
- CatchDecl->getType()->isObjCQualifiedIdType()) {
- llvm::Value *IDEHType =
- CGM.getModule().getGlobalVariable("OBJC_EHTYPE_id");
- if (!IDEHType)
- IDEHType =
+ if (CatchParam->getType()->isObjCIdType() ||
+ CatchParam->getType()->isObjCQualifiedIdType()) {
+ // This is an Objective-C "id" type.
+ ExcTyId = CGM.getModule().getGlobalVariable("OBJC_EHTYPE_id");
+ if (!ExcTyId)
+ ExcTyId =
new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.EHTypeTy,
false,
llvm::GlobalValue::ExternalLinkage,
0, "OBJC_EHTYPE_id");
- SelectorArgs.push_back(IDEHType);
} else {
// All other types should be Objective-C interface pointer types.
const ObjCObjectPointerType *PT =
- CatchDecl->getType()->getAs<ObjCObjectPointerType>();
+ CatchParam->getType()->getAs<ObjCObjectPointerType>();
assert(PT && "Invalid @catch type.");
const ObjCInterfaceType *IT = PT->getInterfaceType();
assert(IT && "Invalid @catch type.");
- llvm::Value *EHType = GetInterfaceEHType(IT->getDecl(), false);
- SelectorArgs.push_back(EHType);
+ ExcTyId = GetInterfaceEHType(IT->getDecl(), false);
}
- }
- }
- }
-
- // We use a cleanup unless there was already a catch all.
- if (!HasCatchAll) {
- // Even though this is a cleanup, treat it as a catch all to avoid the C++
- // personality behavior of terminating the process if only cleanups are
- // found in the exception handling stack.
- SelectorArgs.push_back(llvm::Constant::getNullValue(ObjCTypes.Int8PtrTy));
- Handlers.push_back(std::make_pair((const ParmVarDecl*) 0, (const Stmt*) 0));
- }
-
- llvm::Value *Selector =
- CGF.Builder.CreateCall(llvm_eh_selector_i64,
- SelectorArgs.begin(), SelectorArgs.end(),
- "selector");
- for (unsigned i = 0, e = Handlers.size(); i != e; ++i) {
- const ParmVarDecl *CatchParam = Handlers[i].first;
- const Stmt *CatchBody = Handlers[i].second;
-
- llvm::BasicBlock *Next = 0;
-
- // The last handler always matches.
- if (i + 1 != e) {
- assert(CatchParam && "Only last handler can be a catch all.");
-
- llvm::BasicBlock *Match = CGF.createBasicBlock("match");
- Next = CGF.createBasicBlock("catch.next");
- llvm::Value *Id =
- CGF.Builder.CreateCall(llvm_eh_typeid_for_i64,
- CGF.Builder.CreateBitCast(SelectorArgs[i+2],
- ObjCTypes.Int8PtrTy));
- CGF.Builder.CreateCondBr(CGF.Builder.CreateICmpEQ(Selector, Id),
- Match, Next);
- CGF.EmitBlock(Match);
- }
+ // Compare the thrown type with the parameter type for this catch block.
+ CatchNextChk = CGF.createBasicBlock("next.catch.chk");
+ llvm::BasicBlock *Match = CGF.createBasicBlock("match");
+ llvm::Value *Id =
+ CGF.Builder.CreateCall(llvm_eh_typeid_for_i64,
+ CGF.Builder.CreateBitCast(ExcTyId,
+ ObjCTypes.Int8PtrTy),
+ "type_id");
+ CGF.Builder.CreateCondBr(CGF.Builder.CreateICmpEQ(Selector, Id,
+ "caught"),
+ Match, CatchNextChk);
+ CGF.EmitBlock(Match);
+ }
- if (CatchBody) {
llvm::BasicBlock *MatchEnd = CGF.createBasicBlock("match.end");
llvm::BasicBlock *MatchHandler = CGF.createBasicBlock("match.handler");
- // Cleanups must call objc_end_catch.
+ // Cleanups must call `objc_begin_catch' and `objc_end_catch'.
//
- // FIXME: It seems incorrect for objc_begin_catch to be inside this
+ // FIXME: It seems incorrect for `objc_begin_catch' to be inside this
// context, but this matches gcc.
CGF.PushCleanupBlock(MatchEnd);
CGF.setInvokeDest(MatchHandler);
@@ -5535,9 +5543,10 @@
ExcObject =
CGF.Builder.CreateBitCast(ExcObject,
CGF.ConvertType(CatchParam->getType()));
- // CatchParam is a ParmVarDecl because of the grammar
- // construction used to handle this, but for codegen purposes
- // we treat this as a local decl.
+
+ // CatchParam is a ParmVarDecl, because of the grammar construction used
+ // to handle this. However, for codegen purposes, we treat this as a
+ // local decl.
CGF.EmitLocalBlockVarDecl(*CatchParam);
CGF.Builder.CreateStore(ExcObject, CGF.GetAddrOfLocalVar(CatchParam));
}
@@ -5550,62 +5559,63 @@
CGF.EmitBlock(MatchHandler);
- llvm::Value *Exc = CGF.Builder.CreateCall(llvm_eh_exception, "exc");
- // We are required to emit this call to satisfy LLVM, even
- // though we don't use the result.
- llvm::SmallVector<llvm::Value*, 8> Args;
- Args.push_back(Exc);
- Args.push_back(ObjCTypes.getEHPersonalityPtr());
- Args.push_back(llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
- 0));
- CGF.Builder.CreateCall(llvm_eh_selector_i64, Args.begin(), Args.end());
- CGF.Builder.CreateStore(Exc, RethrowPtr);
CGF.EmitBranchThroughCleanup(FinallyRethrow);
CodeGenFunction::CleanupBlockInfo Info = CGF.PopCleanupBlock();
CGF.EmitBlock(MatchEnd);
- // Unfortunately, we also have to generate another EH frame here
- // in case this throws.
llvm::BasicBlock *MatchEndHandler =
CGF.createBasicBlock("match.end.handler");
llvm::BasicBlock *Cont = CGF.createBasicBlock("invoke.cont");
+ llvm::SmallVector<llvm::Value*, 1> Args;
CGF.Builder.CreateInvoke(ObjCTypes.getObjCEndCatchFn(),
Cont, MatchEndHandler,
Args.begin(), Args.begin());
-
CGF.EmitBlock(Cont);
+
if (Info.SwitchBlock)
CGF.EmitBlock(Info.SwitchBlock);
if (Info.EndBlock)
CGF.EmitBlock(Info.EndBlock);
CGF.EmitBlock(MatchEndHandler);
- Exc = CGF.Builder.CreateCall(llvm_eh_exception, "exc");
- // We are required to emit this call to satisfy LLVM, even
- // though we don't use the result.
- Args.clear();
- Args.push_back(Exc);
- Args.push_back(ObjCTypes.getEHPersonalityPtr());
- Args.push_back(llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
- 0));
- CGF.Builder.CreateCall(llvm_eh_selector_i64, Args.begin(), Args.end());
- CGF.Builder.CreateStore(Exc, RethrowPtr);
+
+ // Unfortunately, we also have to generate the eh.exception and
+ // eh.landingpad calls here in case the invoke above throws.
+ llvm::Value *RethrowExc =
+ CGF.Builder.CreateCall(llvm_eh_exception, "rethrow_exc");
+ llvm::SmallVector<llvm::Value*, 4> LPArgs;
+ LPArgs.push_back(Exc);
+ LPArgs.push_back(ObjCTypes.getEHPersonalityPtr());
+ LPArgs.push_back(llvm::Constant::getNullValue(ObjCTypes.Int8PtrTy));
+ CGF.Builder.CreateCall(llvm_eh_landingpad_i64,
+ LPArgs.begin(), LPArgs.end(), "rethrow_sel");
+ CGF.Builder.CreateStore(RethrowExc, RethrowPtr);
CGF.EmitBranchThroughCleanup(FinallyRethrow);
- if (Next)
- CGF.EmitBlock(Next);
- } else {
- assert(!Next && "catchup should be last handler.");
+ if (CatchNextChk)
+ CGF.EmitBlock(CatchNextChk);
+
+ if (!CatchParam) {
+ // This was the catch-all block. Nothing else can catch beyond this
+ // point.
+ HasCatchAll = true;
+ break;
+ }
+ }
+ // We use a cleanup unless there was already a catch all.
+ if (!HasCatchAll) {
+ // Even though this is a cleanup, treat it as a catch all to avoid the C++
+ // personality behavior of terminating the process if only cleanups are
+ // found in the exception handling stack.
CGF.Builder.CreateStore(Exc, RethrowPtr);
CGF.EmitBranchThroughCleanup(FinallyRethrow);
}
}
- // Pop the cleanup entry, the @finally is outside this cleanup
- // scope.
+ // Pop the cleanup entry, the @finally is outside this cleanup scope.
CodeGenFunction::CleanupBlockInfo Info = CGF.PopCleanupBlock();
CGF.setInvokeDest(PrevLandingPad);
@@ -5616,7 +5626,7 @@
cast<ObjCAtTryStmt>(S).getFinallyStmt())
CGF.EmitStmt(FinallyStmt->getFinallyBody());
} else {
- // Emit 'objc_sync_exit(expr)' as finally's sole statement for
+ // Emit `objc_sync_exit(expr)' as finally's sole statement for
// @synchronized.
CGF.Builder.CreateCall(ObjCTypes.getSyncExitFn(), SyncArg);
}
More information about the llvm-branch-commits
mailing list