llvm-project/clang/lib/CodeGen
Alexander Potapenko 1b5e38a6c9 [CodeGen]: don't treat structures returned in registers as memory inputs
Summary:
The "=r" output constraint for a structure variable passed to inline asm
shouldn't be converted to "=*r", as this changes the asm directive
semantics and prevents DSE optimizations.
Instead, preserve the constraints and return such structures as integers
of corresponding size, which are converted back to structures when
storing the result.

Fixes PR42672.

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65234

llvm-svn: 370335
2019-08-29 11:21:41 +00:00
..
ABIInfo.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
Address.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
BackendUtil.cpp [LTO] Always mark regular LTO units with EnableSplitLTOUnit=1 under the new pass manager 2019-08-21 17:24:14 +00:00
CGAtomic.cpp add periods 2019-04-03 22:19:07 +00:00
CGBlocks.cpp [CodeGen][ObjC] Annotate retain-agnostic ObjC globals with attribute 2019-06-14 22:06:28 +00:00
CGBlocks.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGBuilder.h Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGBuiltin.cpp Builtins: Start adding half versions of math builtins 2019-08-06 03:28:37 +00:00
CGCUDANV.cpp [clang][CodeGen] Remove std::move on temporary 2019-06-17 14:23:06 +00:00
CGCUDARuntime.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGCUDARuntime.h [HIP] Add the interface deriving the stub name of device kernels. 2019-06-17 12:51:36 +00:00
CGCXX.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGCXXABI.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGCXXABI.h [OpenCL] Improve destructor support in C++ for OpenCL 2019-07-22 09:39:13 +00:00
CGCall.cpp [Clang] Migrate llvm::make_unique to std::make_unique 2019-08-14 23:04:18 +00:00
CGCall.h [opaque pointer types] Make EmitCall pass Function Types to 2019-02-07 01:15:41 +00:00
CGClass.cpp [OpenCL] Improve destructor support in C++ for OpenCL 2019-07-22 09:39:13 +00:00
CGCleanup.cpp [NFC] avoid AlignedCharArray in clang 2019-07-29 23:12:48 +00:00
CGCleanup.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGCoroutine.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGDebugInfo.cpp Debug Info: Support for DW_AT_export_symbols for anonymous structs 2019-08-27 20:17:35 +00:00
CGDebugInfo.h Revert "[CGDebugInfo] Simplify EmitFunctionDecl parameters, NFC" 2019-07-11 19:28:07 +00:00
CGDecl.cpp [OpenMP 5.0] Codegen support for user-defined mappers. 2019-08-05 18:43:21 +00:00
CGDeclCXX.cpp Revert r369458 "[DebugInfo] Add debug location to dynamic atexit destructor" 2019-08-22 09:07:25 +00:00
CGException.cpp Updated the signature for some stack related intrinsics (CLANG) 2019-07-22 12:50:30 +00:00
CGExpr.cpp Implement codegen for MSVC unions with reference members. 2019-08-27 12:42:45 +00:00
CGExprAgg.cpp Revert "Revert "CodeGen: ensure placeholder instruction for cleanup is created"" 2019-07-25 20:59:48 +00:00
CGExprCXX.cpp Recommit Devirtualize destructor of final class. 2019-08-08 18:00:49 +00:00
CGExprComplex.cpp [C++2a] Add __builtin_bit_cast, used to implement std::bit_cast 2019-07-02 18:28:13 +00:00
CGExprConstant.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGExprScalar.cpp Treat the range of representable values of floating-point types as [-inf, +inf] not as [-max, +max]. 2019-07-06 21:05:52 +00:00
CGGPUBuiltin.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGLoopInfo.cpp Don't keep stale pointers to LoopInfos. 2019-08-19 13:37:41 +00:00
CGLoopInfo.h Don't keep stale pointers to LoopInfos. 2019-08-19 13:37:41 +00:00
CGNonTrivialStruct.cpp Do a sweep of symbol internalization. NFC. 2019-08-23 19:59:23 +00:00
CGObjC.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CGObjCGNU.cpp [gnustep-objc] Make the GNUstep v2 ABI work for Windows DLLs. 2019-03-31 11:22:33 +00:00
CGObjCMac.cpp Silence gcc warning "control reaches end of non-void function" [NFCI] 2019-07-05 06:12:24 +00:00
CGObjCRuntime.cpp [opaque pointer types] Pass function types for runtime function calls. 2019-02-05 16:42:33 +00:00
CGObjCRuntime.h [opaque pointer types] Pass function types for runtime function calls. 2019-02-05 16:42:33 +00:00
CGOpenCLRuntime.cpp [OpenCL] Simplify LLVM IR generated for OpenCL blocks 2019-02-21 11:02:10 +00:00
CGOpenCLRuntime.h [OpenCL] Simplify LLVM IR generated for OpenCL blocks 2019-02-21 11:02:10 +00:00
CGOpenMPRuntime.cpp [OPENMP5]Use nonmonotonic modifier by default for non-static and 2019-08-23 19:52:05 +00:00
CGOpenMPRuntime.h [OpenMP 5.0] Codegen support for user-defined mappers. 2019-08-05 18:43:21 +00:00
CGOpenMPRuntimeNVPTX.cpp [OPENMP][NVPTX]Fix critical region codegen. 2019-08-26 19:07:48 +00:00
CGOpenMPRuntimeNVPTX.h [OpenMP] Add support for registering requires directives with the runtime 2019-05-21 19:42:01 +00:00
CGRecordLayout.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGRecordLayoutBuilder.cpp P0840R2: support for [[no_unique_address]] attribute 2019-06-20 20:44:45 +00:00
CGStmt.cpp [CodeGen]: don't treat structures returned in registers as memory inputs 2019-08-29 11:21:41 +00:00
CGStmtOpenMP.cpp [OPENMP5.0]Add support for device_type clause in declare target 2019-08-23 16:11:14 +00:00
CGVTT.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGVTables.cpp [CodeGen] Set construction vtable visibility after creating initializer 2019-02-11 20:13:42 +00:00
CGVTables.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CGValue.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CMakeLists.txt Make CodeGen depend on ASTMatchers 2019-06-26 14:13:43 +00:00
CodeGenABITypes.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CodeGenAction.cpp [Support][Time profiler] Make FE codegen blocks to be inside frontend blocks 2019-08-19 22:58:26 +00:00
CodeGenFunction.cpp Fix always_inline 'target' compatibility check code for Lambdas 2019-08-28 20:59:25 +00:00
CodeGenFunction.h [OpenCL] Improve destructor support in C++ for OpenCL 2019-07-22 09:39:13 +00:00
CodeGenModule.cpp [OPENMP5.0]Add support for device_type clause in declare target 2019-08-23 16:11:14 +00:00
CodeGenModule.h C++ DR712 and others: handle non-odr-use resulting from an lvalue-to-rvalue conversion applied to a member access or similar not-quite-trivial lvalue expression. 2019-06-14 17:46:37 +00:00
CodeGenPGO.cpp [Clang] Migrate llvm::make_unique to std::make_unique 2019-08-14 23:04:18 +00:00
CodeGenPGO.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CodeGenTBAA.cpp Fix TBAA representation for zero-sized fields and unnamed bit-fields. 2019-06-22 21:30:43 +00:00
CodeGenTBAA.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CodeGenTypeCache.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CodeGenTypes.cpp Add SVE opaque built-in types 2019-08-09 08:52:54 +00:00
CodeGenTypes.h IRGen: Remove StructorType; thread GlobalDecl through more code. NFCI. 2019-03-22 23:05:10 +00:00
ConstantEmitter.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
ConstantInitBuilder.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
CoverageMappingGen.cpp Fix parameter name comments using clang-tidy. NFC. 2019-07-16 04:46:31 +00:00
CoverageMappingGen.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
EHScopeStack.h Replace llvm::integer_sequence and friends with the C++14 standard version 2019-08-15 10:56:05 +00:00
ItaniumCXXABI.cpp Add SVE opaque built-in types 2019-08-09 08:52:54 +00:00
MacroPPCallbacks.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
MacroPPCallbacks.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
MicrosoftCXXABI.cpp [OpenCL] Improve destructor support in C++ for OpenCL 2019-07-22 09:39:13 +00:00
ModuleBuilder.cpp [OpenMP 5.0] Codegen support for user-defined mappers. 2019-08-05 18:43:21 +00:00
ObjectFilePCHContainerOperations.cpp [Clang] Migrate llvm::make_unique to std::make_unique 2019-08-14 23:04:18 +00:00
PatternInit.cpp CodeGet: Init 32bit pointers with 0xFFFFFFFF 2019-07-12 17:21:55 +00:00
PatternInit.h Variable auto-init: also auto-init alloca 2019-04-12 00:11:27 +00:00
README.txt
SanitizerMetadata.cpp ARM MTE stack sanitizer. 2019-07-15 20:02:23 +00:00
SanitizerMetadata.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
SwiftCallingConv.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
TargetInfo.cpp AMDGPU: Always emit amdgpu-flat-work-group-size 2019-08-27 19:25:40 +00:00
TargetInfo.h [OpenCL][PR41727] Prevent ICE on global dtors 2019-07-15 11:58:10 +00:00
VarBypassDetector.cpp Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
VarBypassDetector.h Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +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!

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