llvm-project/clang/lib/CodeGen
Eric Christopher 9c13eeac99 Update comments.
llvm-svn: 140531
2011-09-26 15:03:22 +00:00
..
ABIInfo.h clang side to match the LLVM IR type system rewrite patch. 2011-07-09 17:41:47 +00:00
BackendUtil.cpp Rename Diagnostic to DiagnosticsEngine as per issue 5397 2011-09-25 23:23:43 +00:00
CGBlocks.cpp Switch LangOptions over to a .def file that describes header of the 2011-09-13 17:21:33 +00:00
CGBlocks.h de-constify llvm::Type, patch by David Blaikie! 2011-07-18 04:24:23 +00:00
CGBuilder.h Make CGBuilderTy a typedef again; its functionality has been rolled back 2010-07-06 18:43:48 +00:00
CGBuiltin.cpp Switch assert(0/false) llvm_unreachable. 2011-09-23 05:06:16 +00:00
CGCXX.cpp Move all vtable layout data into new VTableLayout class 2011-09-26 01:56:50 +00:00
CGCXXABI.cpp Rename Diagnostic to DiagnosticsEngine as per issue 5397 2011-09-25 23:23:43 +00:00
CGCXXABI.h clean up forward declarations of raw_ostream to use the new LLVM.h 2011-07-23 10:35:09 +00:00
CGCall.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGCall.h now that we have a centralized place to do so, add some using declarations for 2011-07-20 06:58:45 +00:00
CGClass.cpp Move all vtable layout data into new VTableLayout class 2011-09-26 01:56:50 +00:00
CGCleanup.cpp Simplify EH control flow by observing that EH scopes form a simple 2011-08-11 02:22:43 +00:00
CGCleanup.h Simplify EH control flow by observing that EH scopes form a simple 2011-08-11 02:22:43 +00:00
CGDebugInfo.cpp Update comments. 2011-09-26 15:03:22 +00:00
CGDebugInfo.h Use new DIBuilder::finalize() at the end to wrap up debug info encoding for a translation unit. 2011-08-15 23:01:55 +00:00
CGDecl.cpp Switch assert(0/false) llvm_unreachable. 2011-09-23 05:06:16 +00:00
CGDeclCXX.cpp Extend the ASTContext constructor to delay the initialization of 2011-09-02 00:18:52 +00:00
CGException.cpp Don't remove filters. 2011-09-22 20:32:54 +00:00
CGException.h now that we have a centralized place to do so, add some using declarations for 2011-07-20 06:58:45 +00:00
CGExpr.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGExprAgg.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGExprCXX.cpp Rewrite this loop to use partial destruction; I'm not sure it's 2011-09-15 06:49:18 +00:00
CGExprComplex.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGExprConstant.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGExprScalar.cpp Treat list-initialization of scalars as a first-class citizen in C++11. 2011-09-24 17:48:14 +00:00
CGObjC.cpp Turn off the generation of unaligned atomic load/store; I'm going to explicitly error out on such cases in the backend, at least for the moment. 2011-09-13 20:48:30 +00:00
CGObjCGNU.cpp Switch assert(0/false) llvm_unreachable. 2011-09-23 05:06:16 +00:00
CGObjCMac.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CGObjCRuntime.cpp Refactor the load of the exception pointer and the exception selector from their 2011-09-15 18:57:19 +00:00
CGObjCRuntime.h Switch assert(0/false) llvm_unreachable. 2011-09-23 05:06:16 +00:00
CGOpenCLRuntime.cpp OpenCL: introduce support for function scope __local variables 2011-09-19 21:14:35 +00:00
CGOpenCLRuntime.h OpenCL: introduce support for function scope __local variables 2011-09-19 21:14:35 +00:00
CGRTTI.cpp Create a VTableContext class and start moving CodeGenVTables methods to it 2011-09-26 01:56:30 +00:00
CGRecordLayout.h clean up forward declarations of raw_ostream to use the new LLVM.h 2011-07-23 10:35:09 +00:00
CGRecordLayoutBuilder.cpp Extend the ASTContext constructor to delay the initialization of 2011-09-02 00:18:52 +00:00
CGStmt.cpp Fix comment to reflect reality. 2011-09-26 15:03:19 +00:00
CGTemporaries.cpp Generalize Cleanup::Emit's "isForEH" parameter into a set 2011-07-12 20:27:29 +00:00
CGVTT.cpp Move all vtable layout data into new VTableLayout class 2011-09-26 01:56:50 +00:00
CGVTables.cpp Move VTable builder to AST 2011-09-26 01:57:12 +00:00
CGVTables.h Move VTable builder to AST 2011-09-26 01:57:12 +00:00
CGValue.h What say we document some of these AggValueSlot flags a bit 2011-08-26 08:02:37 +00:00
CMakeLists.txt OpenCL: introduce support for function scope __local variables 2011-09-19 21:14:35 +00:00
CodeGenAction.cpp Rename Diagnostic to DiagnosticsEngine as per issue 5397 2011-09-25 23:23:43 +00:00
CodeGenFunction.cpp Throw the switch to convert clang to the new exception handling model! 2011-09-19 20:31:14 +00:00
CodeGenFunction.h Throw the switch to convert clang to the new exception handling model! 2011-09-19 20:31:14 +00:00
CodeGenModule.cpp Rename Diagnostic to DiagnosticsEngine as per issue 5397 2011-09-25 23:23:43 +00:00
CodeGenModule.h Create a VTableContext class and start moving CodeGenVTables methods to it 2011-09-26 01:56:30 +00:00
CodeGenTBAA.cpp remove unneeded llvm:: namespace qualifiers on some core types now that LLVM.h imports 2011-07-23 10:55:15 +00:00
CodeGenTBAA.h now that we have a centralized place to do so, add some using declarations for 2011-07-20 06:58:45 +00:00
CodeGenTypes.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
CodeGenTypes.h now that we have a centralized place to do so, add some using declarations for 2011-07-20 06:58:45 +00:00
ItaniumCXXABI.cpp Create a VTableContext class and start moving CodeGenVTables methods to it 2011-09-26 01:56:30 +00:00
Makefile BUILD_ARCHIVE is the default for libraries, no need to set it. 2010-07-18 00:14:47 +00:00
MicrosoftCXXABI.cpp remove unneeded llvm:: namespace qualifiers on some core types now that LLVM.h imports 2011-07-23 10:55:15 +00:00
ModuleBuilder.cpp Rename Diagnostic to DiagnosticsEngine as per issue 5397 2011-09-25 23:23:43 +00:00
README.txt These IRgen improvements have been done. 2009-07-23 03:03:07 +00:00
TargetInfo.cpp Removing a bunch of dead returns/breaks after llvm_unreachables. 2011-09-23 20:26:49 +00:00
TargetInfo.h ANSI C requires that a call to an unprototyped function type succeed 2011-09-21 08:08:30 +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!

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