Cross Reference: /external/clang/lib/CodeGen/

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!

//===---------------------------------------------------------------------===//
Name	Date	Size
..	12-Mar-2015	4 KiB
ABIInfo.h	12-Mar-2015	2.3 KiB
Android.mk	12-Mar-2015	1.7 KiB
BackendUtil.cpp	12-Mar-2015	21.7 KiB
CGAtomic.cpp	12-Mar-2015	43.8 KiB
CGBlocks.cpp	12-Mar-2015	83.3 KiB
CGBlocks.h	12-Mar-2015	7.8 KiB
CGBuilder.h	12-Mar-2015	1.6 KiB
CGBuiltin.cpp	12-Mar-2015	254.5 KiB
CGCall.cpp	12-Mar-2015	116.9 KiB
CGCall.h	12-Mar-2015	5.2 KiB
CGClass.cpp	12-Mar-2015	81 KiB
CGCleanup.cpp	12-Mar-2015	41.7 KiB
CGCleanup.h	12-Mar-2015	16.1 KiB
CGCUDANV.cpp	12-Mar-2015	4.3 KiB
CGCUDARuntime.cpp	12-Mar-2015	1.9 KiB
CGCUDARuntime.h	12-Mar-2015	1.4 KiB
CGCXX.cpp	12-Mar-2015	14.2 KiB
CGCXXABI.cpp	12-Mar-2015	12 KiB
CGCXXABI.h	12-Mar-2015	22.9 KiB
CGDebugInfo.cpp	12-Mar-2015	128.4 KiB
CGDebugInfo.h	12-Mar-2015	19.6 KiB
CGDecl.cpp	12-Mar-2015	64.3 KiB
CGDeclCXX.cpp	12-Mar-2015	20.7 KiB
CGException.cpp	12-Mar-2015	58.4 KiB
CGExpr.cpp	12-Mar-2015	130 KiB
CGExprAgg.cpp	12-Mar-2015	55.3 KiB
CGExprComplex.cpp	12-Mar-2015	32.9 KiB
CGExprConstant.cpp	12-Mar-2015	52.8 KiB
CGExprCXX.cpp	12-Mar-2015	68.6 KiB
CGExprScalar.cpp	12-Mar-2015	126.8 KiB
CGLoopInfo.cpp	12-Mar-2015	3.6 KiB
CGLoopInfo.h	12-Mar-2015	4.3 KiB
CGObjC.cpp	12-Mar-2015	116.4 KiB
CGObjCGNU.cpp	12-Mar-2015	121.4 KiB
CGObjCMac.cpp	12-Mar-2015	277.2 KiB
CGObjCRuntime.cpp	12-Mar-2015	14.1 KiB
CGObjCRuntime.h	12-Mar-2015	12.9 KiB
CGOpenCLRuntime.cpp	12-Mar-2015	2.6 KiB
CGOpenCLRuntime.h	12-Mar-2015	1.4 KiB
CGOpenMPRuntime.cpp	12-Mar-2015	7 KiB
CGOpenMPRuntime.h	12-Mar-2015	6.7 KiB
CGRecordLayout.h	12-Mar-2015	7.9 KiB
CGRecordLayoutBuilder.cpp	12-Mar-2015	34.1 KiB
CGStmt.cpp	12-Mar-2015	77.9 KiB
CGStmtOpenMP.cpp	12-Mar-2015	3.8 KiB
CGValue.h	12-Mar-2015	15.4 KiB
CGVTables.cpp	12-Mar-2015	29.4 KiB
CGVTables.h	12-Mar-2015	4.5 KiB
CGVTT.cpp	12-Mar-2015	6.5 KiB
CMakeLists.txt	12-Mar-2015	1.1 KiB
CodeGenABITypes.cpp	12-Mar-2015	2.4 KiB
CodeGenAction.cpp	12-Mar-2015	27.3 KiB
CodeGenFunction.cpp	12-Mar-2015	61.1 KiB
CodeGenFunction.h	12-Mar-2015	114.1 KiB
CodeGenModule.cpp	12-Mar-2015	125.9 KiB
CodeGenModule.h	12-Mar-2015	41.3 KiB
CodeGenPGO.cpp	12-Mar-2015	36.2 KiB
CodeGenPGO.h	12-Mar-2015	9 KiB
CodeGenTBAA.cpp	12-Mar-2015	11.1 KiB
CodeGenTBAA.h	12-Mar-2015	5.4 KiB
CodeGenTypes.cpp	12-Mar-2015	26 KiB
CodeGenTypes.h	12-Mar-2015	11 KiB
EHScopeStack.h	12-Mar-2015	16.6 KiB
ItaniumCXXABI.cpp	12-Mar-2015	112.9 KiB
Makefile	12-Mar-2015	597
MicrosoftCXXABI.cpp	12-Mar-2015	116.6 KiB
ModuleBuilder.cpp	12-Mar-2015	6.2 KiB
README.txt	12-Mar-2015	1.8 KiB
SanitizerBlacklist.cpp	12-Mar-2015	1.7 KiB
SanitizerBlacklist.h	12-Mar-2015	1.3 KiB
TargetInfo.cpp	12-Mar-2015	238.5 KiB
TargetInfo.h	12-Mar-2015	8.6 KiB