Improve MemCopyOpt heuristics to account for combinable stores #5
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Avoid changing multiple stores to 'memset' calls when when the stores can be combined into a smaller number of stores by SelectionDAG when some alignment information is available on some stores.
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For the following program,
$ cat t.c
struct t {
int (__attribute__((btf_type_tag("rcu"))) *f)();
int a;
};
int foo(struct t *arg) {
return arg->a;
}
Compiling with 'clang -g -O2 -S t.c' will cause a failure like below:
clang: /home/yhs/work/llvm-project/clang/lib/Sema/SemaType.cpp:6391: void {anonymous}::DeclaratorLocFiller::VisitParenTypeLoc(clang::ParenTypeLoc):
Assertion `Chunk.Kind == DeclaratorChunk::Paren' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
......
#5 0x00007f89e4280ea5 abort (/lib64/libc.so.6+0x21ea5)
#6 0x00007f89e4280d79 _nl_load_domain.cold.0 (/lib64/libc.so.6+0x21d79)
#7 0x00007f89e42a6456 (/lib64/libc.so.6+0x47456)
#8 0x00000000045c2596 GetTypeSourceInfoForDeclarator((anonymous namespace)::TypeProcessingState&, clang::QualType, clang::TypeSourceInfo*) SemaType.cpp:0:0
#9 0x00000000045ccfa5 GetFullTypeForDeclarator((anonymous namespace)::TypeProcessingState&, clang::QualType, clang::TypeSourceInfo*) SemaType.cpp:0:0
......
The reason of the failure is due to the mismatch of TypeLoc and D.getTypeObject().Kind. For example,
the TypeLoc is
BTFTagAttributedType 0x88614e0 'int btf_type_tag(rcu)()' sugar
|-ParenType 0x8861480 'int ()' sugar
| `-FunctionNoProtoType 0x8861450 'int ()' cdecl
| `-BuiltinType 0x87fd500 'int'
while corresponding D.getTypeObject().Kind points to DeclaratorChunk::Paren, and
this will cause later assertion.
To fix the issue, similar to AttributedTypeLoc, let us skip BTFTagAttributedTypeLoc in
GetTypeSourceInfoForDeclarator().
Differential Revision: https://reviews.llvm.org/D136807
farazs-github
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Mar 11, 2024
…euristics Improve MemCopyOpt heuristics to account for combinable stores
milica-lazarevic
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Jun 18, 2024
…euristics Improve MemCopyOpt heuristics to account for combinable stores
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Avoid changing multiple stores to 'memset' calls when when the stores can be combined into a smaller number of stores by SelectionDAG when some alignment information is available on some stores.