forked from OSchip/llvm-project
7dc5c17d92
that is in an anonymous namespace, give that function or variable
internal linkage.
This change models an oddity of the C++ standard, where names declared
in an anonymous namespace have external linkage but, because anonymous
namespace are really "uniquely-named" namespaces, the names cannot be
referenced from other translation units. That means that they have
external linkage for semantic analysis, but the only sensible
implementation for code generation is to give them internal
linkage. We now model this notion via the UniqueExternalLinkage
linkage type. There are several changes here:
- Extended NamedDecl::getLinkage() to produce UniqueExternalLinkage
when the declaration is in an anonymous namespace.
- Added Type::getLinkage() to determine the linkage of a type, which
is defined as the minimum linkage of the types (when we're dealing
with a compound type that is not a struct/class/union).
- Extended NamedDecl::getLinkage() to consider the linkage of the
template arguments and template parameters of function template
specializations and class template specializations.
- Taught code generation to rely on NamedDecl::getLinkage() when
determining the linkage of variables and functions, also
considering the linkage of the types of those variables and
functions (C++ only). Map UniqueExternalLinkage to internal
linkage, taking out the explicit checks for
isInAnonymousNamespace().
This fixes much of PR5792, which, as discovered by Anders Carlsson, is
actually the reason behind the pass-manager assertion that causes the
majority of clang-on-clang regression test failures. With this fix,
Clang-built-Clang+LLVM passes 88% of its regression tests (up from
67%). The specific numbers are:
LLVM:
Expected Passes : 4006
Expected Failures : 32
Unsupported Tests : 40
Unexpected Failures: 736
Clang:
Expected Passes : 1903
Expected Failures : 14
Unexpected Failures: 75
Overall:
Expected Passes : 5909
Expected Failures : 46
Unsupported Tests : 40
Unexpected Failures: 811
Still to do:
- Improve testing
- Check whether we should allow the presence of types with
InternalLinkage (in addition to UniqueExternalLinkage) given
variables/functions internal linkage in C++, as mentioned in
PR5792.
- Determine how expensive the getLinkage() calls are in practice;
consider caching the result in NamedDecl.
- Assess the feasibility of Chris's idea in comment #1 of PR5792.
llvm-svn: 95216
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||
|---|---|---|
| .. | ||
| ABIInfo.h | ||
| CGBlocks.cpp | ||
| CGBlocks.h | ||
| CGBuilder.h | ||
| CGBuiltin.cpp | ||
| CGCXX.cpp | ||
| CGCXX.h | ||
| CGCall.cpp | ||
| CGCall.h | ||
| CGClass.cpp | ||
| CGDebugInfo.cpp | ||
| CGDebugInfo.h | ||
| CGDecl.cpp | ||
| CGDeclCXX.cpp | ||
| CGException.cpp | ||
| CGExpr.cpp | ||
| CGExprAgg.cpp | ||
| CGExprCXX.cpp | ||
| CGExprComplex.cpp | ||
| CGExprConstant.cpp | ||
| CGExprScalar.cpp | ||
| CGObjC.cpp | ||
| CGObjCGNU.cpp | ||
| CGObjCMac.cpp | ||
| CGObjCRuntime.h | ||
| CGRTTI.cpp | ||
| CGRecordLayoutBuilder.cpp | ||
| CGRecordLayoutBuilder.h | ||
| CGStmt.cpp | ||
| CGTemporaries.cpp | ||
| CGVTT.cpp | ||
| CGValue.h | ||
| CGVtable.cpp | ||
| CGVtable.h | ||
| CMakeLists.txt | ||
| CodeGenFunction.cpp | ||
| CodeGenFunction.h | ||
| CodeGenModule.cpp | ||
| CodeGenModule.h | ||
| CodeGenTypes.cpp | ||
| CodeGenTypes.h | ||
| GlobalDecl.h | ||
| Makefile | ||
| Mangle.cpp | ||
| Mangle.h | ||
| ModuleBuilder.cpp | ||
| README.txt | ||
| TargetInfo.cpp | ||
| TargetInfo.h | ||
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! //===---------------------------------------------------------------------===//