llvm-project/clang/lib/CodeGen
Akira Hatanaka 7828b1e604 Add support for function attribute 'disable_tail_calls'.
The ``disable_tail_calls`` attribute instructs the backend to not
perform tail call optimization inside the marked function.

For example, 

int callee(int);

int foo(int a) __attribute__((disable_tail_calls)) {
  return callee(a); // This call is not tail-call optimized.
}

Note that this attribute is different from 'not_tail_called', which
prevents tail-call optimization to the marked function.

rdar://problem/8973573

Differential Revision: http://reviews.llvm.org/D12547

llvm-svn: 252986
2015-11-13 00:42:21 +00:00
..
ABIInfo.h Support __builtin_ms_va_list. 2015-09-17 20:55:33 +00:00
Address.h PR25368: Replace workaround for build failure with modules enabled with a fix 2015-11-05 21:16:22 +00:00
BackendUtil.cpp [ASan] Allow -fsanitize-recover=address. 2015-11-11 10:45:48 +00:00
CGAtomic.cpp Correct atomic libcall support for __atomic_*_fetch builtins. 2015-11-12 18:37:29 +00:00
CGBlocks.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGBlocks.h Move BlockByrefHelpers back to CodeGenModule.h to placate MSVC. 2015-09-08 08:21:11 +00:00
CGBuilder.h Remove unnecessary braces; this resolves against a 2015-09-08 08:57:00 +00:00
CGBuiltin.cpp Move checkTargetFeatures to CodeGenFunction.cpp to make it 2015-11-12 00:44:07 +00:00
CGCUDANV.cpp Compute and preserve alignment more faithfully in IR-generation. 2015-09-08 08:05:57 +00:00
CGCUDARuntime.cpp Roll-back r250822. 2015-10-20 13:23:58 +00:00
CGCUDARuntime.h Revert r240270 ("Fixed/added namespace ending comments using clang-tidy"). 2015-06-22 23:07:51 +00:00
CGCXX.cpp [COFF] Don't try to emit weak aliases on COFF 2015-11-10 22:23:58 +00:00
CGCXXABI.cpp [MS ABI] Don't zero-initialize vbptrs in bases 2015-11-02 09:01:44 +00:00
CGCXXABI.h [MS ABI] Don't zero-initialize vbptrs in bases 2015-11-02 09:01:44 +00:00
CGCall.cpp Add support for function attribute 'disable_tail_calls'. 2015-11-13 00:42:21 +00:00
CGCall.h Don't emit exceptional stackrestore cleanups around inalloca functions 2015-10-08 00:17:45 +00:00
CGClass.cpp Fix Clang-tidy modernize-use-nullptr warnings in source directories; other minor cleanups 2015-10-06 23:40:43 +00:00
CGCleanup.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGCleanup.h [WinEH] Remove NewMSEH and enable its behavior by default 2015-10-08 01:13:52 +00:00
CGDebugInfo.cpp CodeGen: Update for debug info API change. 2015-11-05 22:04:14 +00:00
CGDebugInfo.h Put back doxygen comment accidentally dropped in r250418. 2015-10-15 16:46:25 +00:00
CGDecl.cpp [Sema] Implement __make_integer_seq 2015-11-04 03:40:30 +00:00
CGDeclCXX.cpp [TLS] move setting tls_guard in tls_init. 2015-11-11 19:19:26 +00:00
CGException.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGExpr.cpp Provide a frontend based error for always_inline functions that require 2015-11-12 00:44:12 +00:00
CGExprAgg.cpp Atomics: support __c11_* calls on _Atomic struct types. 2015-11-09 19:56:35 +00:00
CGExprCXX.cpp Remove unused #include 2015-11-03 16:32:15 +00:00
CGExprComplex.cpp [DEBUG INFO] Emit debug info for type used in explicit cast only. 2015-10-20 04:24:12 +00:00
CGExprConstant.cpp PR25368: Replace workaround for build failure with modules enabled with a fix 2015-11-05 21:16:22 +00:00
CGExprScalar.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGLoopInfo.cpp Add new llvm.loop.unroll.enable metadata for use with "#pragma unroll". 2015-08-10 17:29:39 +00:00
CGLoopInfo.h Add new llvm.loop.unroll.enable metadata for use with "#pragma unroll". 2015-08-10 17:29:39 +00:00
CGObjC.cpp [CodeGen] Attach function attributes to Objective-C and OpenMP 2015-10-28 02:30:47 +00:00
CGObjCGNU.cpp Watch and TV OS: wire up basic ABI choices 2015-10-30 16:30:36 +00:00
CGObjCMac.cpp Watch and TV OS: wire up basic ABI choices 2015-10-30 16:30:36 +00:00
CGObjCRuntime.cpp Initialize @catch variables correctly in fragile-runtime ARC. 2015-10-30 00:56:02 +00:00
CGObjCRuntime.h Initialize @catch variables correctly in fragile-runtime ARC. 2015-10-30 00:56:02 +00:00
CGOpenCLRuntime.cpp Roll-back r250822. 2015-10-20 13:23:58 +00:00
CGOpenCLRuntime.h Revert r240270 ("Fixed/added namespace ending comments using clang-tidy"). 2015-06-22 23:07:51 +00:00
CGOpenMPRuntime.cpp [CodeGen] Call SetInternalFunctionAttributes to attach function 2015-10-31 01:28:07 +00:00
CGOpenMPRuntime.h Roll-back r250822. 2015-10-20 13:23:58 +00:00
CGRecordLayout.h Respect alignment of nested bitfields 2015-07-10 17:30:00 +00:00
CGRecordLayoutBuilder.cpp [MS ABI] Don't crash when inheriting from base with trailing empty array member 2015-10-22 18:04:22 +00:00
CGStmt.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGStmtOpenMP.cpp CGStmtOpenMP.cpp: Prune redundant \param. [-Wdocumentation] 2015-10-08 16:41:42 +00:00
CGVTT.cpp Remove and forbid raw_svector_ostream::flush() calls. 2015-08-13 18:12:56 +00:00
CGVTables.cpp CodeGen: Remove implicit ilist iterator conversions, NFC 2015-11-06 23:00:41 +00:00
CGVTables.h [CodeGen] Remove dead code. NFC. 2015-10-15 15:29:40 +00:00
CGValue.h Introduce __builtin_nontemporal_store and __builtin_nontemporal_load. 2015-09-08 23:52:33 +00:00
CMakeLists.txt [CMake] Fill up required libs, corresponding to r241653. 2015-07-08 02:06:21 +00:00
CodeGenABITypes.cpp Put back dead code that's used out-of-tree. 2015-10-20 07:50:21 +00:00
CodeGenAction.cpp Allow linking multiple bitcode files. 2015-10-27 17:56:59 +00:00
CodeGenFunction.cpp [C++] Add the "norecurse" attribute to main() if in C++ mode 2015-11-12 15:36:04 +00:00
CodeGenFunction.h In preparation to use it in more places rename 2015-11-12 00:44:04 +00:00
CodeGenModule.cpp [TLS on Darwin] treat all Darwin platforms in the same way. 2015-11-11 23:08:18 +00:00
CodeGenModule.h Extract out a function onto CodeGenModule for getting the map of 2015-11-11 23:05:08 +00:00
CodeGenPGO.cpp [PGO] Code cleanup [NFC] 2015-11-09 00:04:16 +00:00
CodeGenPGO.h [CodeGen] Remove dead code. NFC. 2015-10-15 15:29:40 +00:00
CodeGenTBAA.cpp Roll-back r250822. 2015-10-20 13:23:58 +00:00
CodeGenTBAA.h Header guard canonicalization, clang part. 2014-08-13 16:25:19 +00:00
CodeGenTypeCache.h Compute and preserve alignment more faithfully in IR-generation. 2015-09-08 08:05:57 +00:00
CodeGenTypes.cpp [OpenCL] Add new types for OpenCL 2.0. 2015-09-15 11:18:52 +00:00
CodeGenTypes.h Remove superfluous private:, TypeCache is private by default. 2015-08-13 07:12:03 +00:00
CoverageMappingGen.cpp Use profile data template file for covmap func record (NFC) 2015-11-05 05:46:39 +00:00
CoverageMappingGen.h [cleanup] Re-sort *all* #include lines with llvm/utils/sort_includes.py 2015-01-14 11:29:14 +00:00
EHScopeStack.h [CodeGen] Remove dead code. NFC. 2015-10-15 15:29:40 +00:00
ItaniumCXXABI.cpp [TLS on Darwin] treat all Darwin platforms in the same way. 2015-11-11 23:08:18 +00:00
Makefile
MicrosoftCXXABI.cpp [MS ABI] Don't zero-initialize vbptrs in bases 2015-11-02 09:01:44 +00:00
ModuleBuilder.cpp [MSVC Compat] Enable ABI impacting non-conforming behavior independently of -fms-compatibility 2015-10-08 04:53:31 +00:00
ObjectFilePCHContainerOperations.cpp Module Debugging: Emit module debug info for types inside of Objective-C 2015-10-23 17:02:22 +00:00
README.txt
SanitizerMetadata.cpp [ASan] Initial support for Kernel AddressSanitizer 2015-06-19 12:19:07 +00:00
SanitizerMetadata.h Removing LLVM_DELETED_FUNCTION, as MSVC 2012 was the last reason for requiring the macro. NFC; Clang edition. 2015-02-15 22:54:08 +00:00
TargetInfo.cpp Remove some legacy mingw-w64 gcc struct info 2015-11-03 15:57:45 +00:00
TargetInfo.h Fix Clang-tidy modernize-use-nullptr warnings in headers and generated files; other minor cleanups. 2015-09-29 20:56:43 +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!

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