llvm-project/clang/lib/CodeGen
Douglas Gregor 7ae2d7758f Rework base and member initialization in constructors, with several
(necessarily simultaneous) changes:

  - CXXBaseOrMemberInitializer now contains only a single initializer
    rather than a set of initialiation arguments + a constructor. The
    single initializer covers all aspects of initialization, including
    constructor calls as necessary but also cleanup of temporaries
    created by the initializer (which we never handled
    before!).

  - Rework + simplify code generation for CXXBaseOrMemberInitializers,
    since we can now just emit the initializer as an initializer.

  - Switched base and member initialization over to the new
    initialization code (InitializationSequence), so that it

  - Improved diagnostics for the new initialization code when
    initializing bases and members, to match the diagnostics produced
    by the previous (special-purpose) code.

  - Simplify the representation of type-checked constructor initializers in
    templates; instead of keeping the fully-type-checked AST, which is
    rather hard to undo at template instantiation time, throw away the
    type-checked AST and store the raw expressions in the AST. This
    simplifies instantiation, but loses a little but of information in
    the AST.

  - When type-checking implicit base or member initializers within a
    dependent context, don't add the generated initializers into the
    AST, because they'll look like they were explicit.

  - Record in CXXConstructExpr when the constructor call is to
  initialize a base class, so that CodeGen does not have to infer it
  from context. This ensures that we call the right kind of
  constructor.

There are also a few "opportunity" fixes here that were needed to not
regress, for example:

  - Diagnose default-initialization of a const-qualified class that
    does not have a user-declared default constructor. We had this
    diagnostic specifically for bases and members, but missed it for
    variables. That's fixed now.

  - When defining the implicit constructors, destructor, and
    copy-assignment operator, set the CurContext to that constructor
    when we're defining the body.

llvm-svn: 94952
2010-01-31 09:12:51 +00:00
..
ABIInfo.h x86-64 ABI: If a type is a C++ record with either a non-trivial destructor or a non-trivial copy constructor, it should be passed in a pointer. Daniel, plz review. 2009-09-16 15:53:40 +00:00
CGBlocks.cpp Change the return type of ASTContext::getDeclAlignInBytes() to CharUnits and, 2010-01-27 17:10:57 +00:00
CGBlocks.h Use CharUnits for alignments in character units. 2010-01-26 19:13:33 +00:00
CGBuilder.h Disable generation of basic block names in NDEBUG mode. 2008-11-12 00:01:12 +00:00
CGBuiltin.cpp Add bzero builtin; this should help codegen quality for code using this 2010-01-23 19:00:10 +00:00
CGCXX.cpp Move a few more functions away from CGCXX and to CGClass and CGExprCXX. 2010-01-01 20:29:01 +00:00
CGCXX.h Remove tabs, and whitespace cleanups. 2009-09-09 15:08:12 +00:00
CGCall.cpp Simplify EmitLValueForField - we can get whether the field is part of a union or not from the FieldDecl (through its DeclContext). 2010-01-29 05:05:36 +00:00
CGCall.h Fill in the return value slot in CGExprAgg::VisitCallExpr. This takes us halfway towards fixing PR5824. 2009-12-24 20:40:36 +00:00
CGClass.cpp Rework base and member initialization in constructors, with several 2010-01-31 09:12:51 +00:00
CGDebugInfo.cpp Use appropriate context for typedefs. 2010-01-29 22:29:31 +00:00
CGDebugInfo.h Maintain a map of regions (lexical scopes) and use it to find context for a global variable. 2010-01-29 18:11:03 +00:00
CGDecl.cpp Change the return type of ASTContext::getDeclAlignInBytes() to CharUnits and, 2010-01-27 17:10:57 +00:00
CGDeclCXX.cpp global variable that binds reference to a non-lvalue reproted 2010-01-25 21:40:39 +00:00
CGException.cpp Fix last patch, catch of reference to non-pointer. 2010-01-01 03:20:32 +00:00
CGExpr.cpp Add a new EmitLValueForFieldInitialization that will be used for initializing fields (and reference type fields in particular). 2010-01-29 05:24:29 +00:00
CGExprAgg.cpp Some class related cleanup. 2010-01-31 01:36:53 +00:00
CGExprCXX.cpp Rework base and member initialization in constructors, with several 2010-01-31 09:12:51 +00:00
CGExprComplex.cpp refactor pre/postinc logic into CGF and require the caller to pass in the 2010-01-09 21:40:03 +00:00
CGExprConstant.cpp Some class related cleanup. 2010-01-31 01:36:53 +00:00
CGExprScalar.cpp Some class related cleanup. 2010-01-31 01:36:53 +00:00
CGObjC.cpp Created __builtin___NSStringMakeConstantString() builtin, which generates constant Objective-C strings. 2010-01-23 02:40:42 +00:00
CGObjCGNU.cpp Unique ObjC strings (GNU Runtime); fix for PR6142. Note: Doing this in the runtime-specific code is a bit ugly. It would be a good idea to hoist all of the string / protocol uniqueing code up into CGObjCRuntime or CodeGenModule and only handle emitting the original versions in the runtime-specific code. 2010-01-27 12:49:23 +00:00
CGObjCMac.cpp Created __builtin___NSStringMakeConstantString() builtin, which generates constant Objective-C strings. 2010-01-23 02:40:42 +00:00
CGObjCRuntime.h Created __builtin___NSStringMakeConstantString() builtin, which generates constant Objective-C strings. 2010-01-23 02:40:42 +00:00
CGRTTI.cpp Fix linkage for RTTI names by re-using the logic for computing the 2010-01-06 22:00:56 +00:00
CGRecordLayoutBuilder.cpp Fix an incorrect union layout assert. Fixes PR6164. 2010-01-28 18:22:03 +00:00
CGRecordLayoutBuilder.h Baby steps towards fixing PR5589. If a class needs a vtable pointer, add one. 2009-12-16 17:27:20 +00:00
CGStmt.cpp More asm cleanup. 2010-01-30 20:05:21 +00:00
CGTemporaries.cpp Fix double-destruction assertion to account for temporaries in conditionals 2009-12-24 18:16:21 +00:00
CGVTT.cpp Move the VTT related code into its own file, CGVTT.cpp 2010-01-21 16:50:45 +00:00
CGValue.h Fix documentation. 2009-11-03 16:11:57 +00:00
CGVtable.cpp Refine the non-virtual this adjustments for thunks by using the offset 2010-01-26 22:44:01 +00:00
CGVtable.h Store the address points for constructor vtables directly in the VTT builder, because that's the only time they're needed. 2010-01-14 02:29:07 +00:00
CMakeLists.txt Move the VTT related code into its own file, CGVTT.cpp 2010-01-21 16:50:45 +00:00
CodeGenFunction.cpp Fix a nasty bug where temporaries weren't marked as being conditional in some cases. 2010-01-24 00:20:05 +00:00
CodeGenFunction.h Some class related cleanup. 2010-01-31 01:36:53 +00:00
CodeGenModule.cpp Change the return type of ASTContext::getDeclAlignInBytes() to CharUnits and, 2010-01-27 17:10:57 +00:00
CodeGenModule.h Some class related cleanup. 2010-01-31 01:36:53 +00:00
CodeGenTypes.cpp Use the new isInteger() method in a couple places, some random cleanup, and 2010-01-11 19:58:10 +00:00
CodeGenTypes.h Generalize target weirdness handling having proper layering in mind: 2010-01-10 12:58:08 +00:00
GlobalDecl.h update to match LLVM API change: 2009-12-15 07:26:51 +00:00
Makefile -fno-rtti is now the default. 2010-01-24 20:43:31 +00:00
Mangle.cpp Name mangling for cast expressions, from Matthias Schiffer! Fixes PR5876. 2010-01-29 16:37:09 +00:00
Mangle.h Work-in-progress: teach mangler how to mangle thunks for destructors. 2009-12-03 00:03:05 +00:00
ModuleBuilder.cpp Remove ';' after method definition. Noticed by clang++, which one would think 2009-12-19 17:50:07 +00:00
README.txt These IRgen improvements have been done. 2009-07-23 03:03:07 +00:00
TargetInfo.cpp ARM/APCS ABI: Fix some problems with bit-fields in structures. After rereading 2010-01-29 03:22:29 +00:00
TargetInfo.h Eliminate some Clang warnings 2010-01-22 15:41:14 +00:00

README.txt

IRgen optimization opportunities.

//===---------------------------------------------------------------------===//

The common pattern of
--
short x; // or char, etc
(x == 10)
--
generates an zext/sext of x which can easily be avoided.

//===---------------------------------------------------------------------===//

Bitfields accesses can be shifted to simplify masking and sign
extension. For example, if the bitfield width is 8 and it is
appropriately aligned then is is a lot shorter to just load the char
directly.

//===---------------------------------------------------------------------===//

It may be worth avoiding creation of alloca's for formal arguments
for the common situation where the argument is never written to or has
its address taken. The idea would be to begin generating code by using
the argument directly and if its address is taken or it is stored to
then generate the alloca and patch up the existing code.

In theory, the same optimization could be a win for block local
variables as long as the declaration dominates all statements in the
block.

NOTE: The main case we care about this for is for -O0 -g compile time
performance, and in that scenario we will need to emit the alloca
anyway currently to emit proper debug info. So this is blocked by
being able to emit debug information which refers to an LLVM
temporary, not an alloca.

//===---------------------------------------------------------------------===//

We should try and avoid generating basic blocks which only contain
jumps. At -O0, this penalizes us all the way from IRgen (malloc &
instruction overhead), all the way down through code generation and
assembly time.

On 176.gcc:expr.ll, it looks like over 12% of basic blocks are just
direct branches!

//===---------------------------------------------------------------------===//