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llvm-project/clang/test/CodeGen/semantic-interposition.c

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[Driver] Move -fsemantic-interposition decision from cc1 to driver And add test/Driver/fsemantic-interposition.c
2020-02-03 11:30:39 +08:00
// RUN: %clang_cc1 -emit-llvm -fsemantic-interposition %s -o - | FileCheck --check-prefix=INTERPOSITION %s
// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck --check-prefix=NO %s
Make explicit -fno-semantic-interposition (in -fpic mode) infer dso_local -fno-semantic-interposition is currently the CC1 default. (The opposite disables some interprocedural optimizations.) However, it does not infer dso_local: on most targets accesses to ExternalLinkage functions/variables defined in the current module still need PLT/GOT. This patch makes explicit -fno-semantic-interposition infer dso_local, so that PLT/GOT can be eliminated if targets implement local aliases for AsmPrinter::getSymbolPreferLocal (currently only x86). Currently we check whether the module flag "SemanticInterposition" is 0. If yes, infer dso_local. In the future, we can infer dso_local unless "SemanticInterposition" is 1: frontends other than clang will also benefit from the optimization if they don't bother setting the flag. (There will be risks if they do want ELF interposition: they need to set "SemanticInterposition" to 1.)
2020-05-26 06:05:35 +08:00
/// With explicit -fno-semantic-interposition, add a module flag to inform the
/// backend that dso_local can be inferred.
// RUN: %clang_cc1 -emit-llvm -fno-semantic-interposition %s -o - | FileCheck --check-prefix=EXPLICIT_NO %s
Implement -fsemantic-interposition First attempt at implementing -fsemantic-interposition. Rely on GlobalValue::isInterposable that already captures most of the expected behavior. Rely on a ModuleFlag to state whether we should respect SemanticInterposition or not. The default remains no. So this should be a no-op if -fsemantic-interposition isn't used, and if it is, isInterposable being already used in most optimisation, they should honor it properly. Note that it only impacts architecture compiled with -fPIC and no pie. Differential Revision: https://reviews.llvm.org/D72829
2020-01-16 18:56:41 +08:00
[Driver] Move -fsemantic-interposition decision from cc1 to driver And add test/Driver/fsemantic-interposition.c
2020-02-03 11:30:39 +08:00
// INTERPOSITION: !{{[0-9]+}} = !{i32 1, !"SemanticInterposition", i32 1}
// NO-NOT: "SemanticInterposition"
Make explicit -fno-semantic-interposition (in -fpic mode) infer dso_local -fno-semantic-interposition is currently the CC1 default. (The opposite disables some interprocedural optimizations.) However, it does not infer dso_local: on most targets accesses to ExternalLinkage functions/variables defined in the current module still need PLT/GOT. This patch makes explicit -fno-semantic-interposition infer dso_local, so that PLT/GOT can be eliminated if targets implement local aliases for AsmPrinter::getSymbolPreferLocal (currently only x86). Currently we check whether the module flag "SemanticInterposition" is 0. If yes, infer dso_local. In the future, we can infer dso_local unless "SemanticInterposition" is 1: frontends other than clang will also benefit from the optimization if they don't bother setting the flag. (There will be risks if they do want ELF interposition: they need to set "SemanticInterposition" to 1.)
2020-05-26 06:05:35 +08:00
// EXPLICIT_NO: !{{[0-9]+}} = !{i32 1, !"SemanticInterposition", i32 0}