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llvm-project/clang/test/CodeGenCXX/new-infallible.cpp

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[clang] Add support for optional flag -fnew-infallible to restrict exception propagation The declaration for the global new function in C++ is generated in the compiler front-end. When examining exception propagation, we found that this is the largest root throw site propagator requiring unwind code to be generated for callers up the stack. Allowing this to be handled immediately with termination stops upward propagation and leads to significantly less landing pads generated. This in turns leads to a performance and .text size win. With `-fnew-infallible` this annotates the declaration with `throw()` and `__attribute__((returns_nonnull))`. `throw()` allows the compiler to assume exceptions do not propagate out of new and eliminate it as a root throw site. Note that the definition of global new is user-replaceable so users should ensure that the one used follows these semantics. Measuring internally, we're seeing at 0.5% CPU win in one of our large internal FB workload. Measuring on clang self-build (cd0a1226b50081e86eb75a89d01e8782423971a0) we get: thinlto/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 153494, "dwarfehprepare.NumNoUnwind": 26309, thinlto_newinfallible/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 143660, "dwarfehprepare.NumNoUnwind": 28744, a 1-143660/153494 = 6.4% reduction in landing pads and a 28744/26309 = 9.3% increase in the number of nounwind functions. Testing: ninja check-all new test case to make sure these attributes are added correctly to global new. Reviewed By: urnathan Differential Revision: https://reviews.llvm.org/D105225
2021-08-03 06:44:10 +08:00
// RUN: %clang_cc1 -emit-llvm -triple x86_64-linux-gnu -fnew-infallible -o - %s | FileCheck %s
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions. I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default. Test updates are made as a separate patch: D108453 Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D105169 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2) This patch updates test files after D105169. Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows: (1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached. (2) The remaining tests are updated manually. Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D108453 Resolve lit failures in clang after 8ca4b3e's land Fix lit test failures in clang-ppc* and clang-x64-windows-msvc Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc Fix internal_clone(aarch64) inline assembly
2021-10-15 18:26:07 +08:00
// CHECK: call noalias noundef nonnull i8* @_Znwm(i64 noundef 4)
[clang] Add support for optional flag -fnew-infallible to restrict exception propagation The declaration for the global new function in C++ is generated in the compiler front-end. When examining exception propagation, we found that this is the largest root throw site propagator requiring unwind code to be generated for callers up the stack. Allowing this to be handled immediately with termination stops upward propagation and leads to significantly less landing pads generated. This in turns leads to a performance and .text size win. With `-fnew-infallible` this annotates the declaration with `throw()` and `__attribute__((returns_nonnull))`. `throw()` allows the compiler to assume exceptions do not propagate out of new and eliminate it as a root throw site. Note that the definition of global new is user-replaceable so users should ensure that the one used follows these semantics. Measuring internally, we're seeing at 0.5% CPU win in one of our large internal FB workload. Measuring on clang self-build (cd0a1226b50081e86eb75a89d01e8782423971a0) we get: thinlto/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 153494, "dwarfehprepare.NumNoUnwind": 26309, thinlto_newinfallible/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 143660, "dwarfehprepare.NumNoUnwind": 28744, a 1-143660/153494 = 6.4% reduction in landing pads and a 28744/26309 = 9.3% increase in the number of nounwind functions. Testing: ninja check-all new test case to make sure these attributes are added correctly to global new. Reviewed By: urnathan Differential Revision: https://reviews.llvm.org/D105225
2021-08-03 06:44:10 +08:00
// CHECK: ; Function Attrs: nobuiltin nounwind allocsize(0)
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions. I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default. Test updates are made as a separate patch: D108453 Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D105169 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2) This patch updates test files after D105169. Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows: (1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached. (2) The remaining tests are updated manually. Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D108453 Resolve lit failures in clang after 8ca4b3e's land Fix lit test failures in clang-ppc* and clang-x64-windows-msvc Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc Fix internal_clone(aarch64) inline assembly
2021-10-15 18:26:07 +08:00
// CHECK-NEXT: declare noundef nonnull i8* @_Znwm(i64 noundef)
[clang] Add support for optional flag -fnew-infallible to restrict exception propagation The declaration for the global new function in C++ is generated in the compiler front-end. When examining exception propagation, we found that this is the largest root throw site propagator requiring unwind code to be generated for callers up the stack. Allowing this to be handled immediately with termination stops upward propagation and leads to significantly less landing pads generated. This in turns leads to a performance and .text size win. With `-fnew-infallible` this annotates the declaration with `throw()` and `__attribute__((returns_nonnull))`. `throw()` allows the compiler to assume exceptions do not propagate out of new and eliminate it as a root throw site. Note that the definition of global new is user-replaceable so users should ensure that the one used follows these semantics. Measuring internally, we're seeing at 0.5% CPU win in one of our large internal FB workload. Measuring on clang self-build (cd0a1226b50081e86eb75a89d01e8782423971a0) we get: thinlto/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 153494, "dwarfehprepare.NumNoUnwind": 26309, thinlto_newinfallible/ "dwarfehprepare.NumCleanupLandingPadsRemaining": 143660, "dwarfehprepare.NumNoUnwind": 28744, a 1-143660/153494 = 6.4% reduction in landing pads and a 28744/26309 = 9.3% increase in the number of nounwind functions. Testing: ninja check-all new test case to make sure these attributes are added correctly to global new. Reviewed By: urnathan Differential Revision: https://reviews.llvm.org/D105225
2021-08-03 06:44:10 +08:00
int *new_infallible = new int;