Win8 baseline: Improve STL Hardening codegen size - #5433
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Stephan T. Lavavej (StephanTLavavej) merged 2 commits intoApr 29, 2025
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…tin_verbose_trap`. + MSVC [`__fastfail`](https://learn.microsoft.com/en-us/cpp/intrinsics/fastfail?view=msvc-170): "Support for the native fast fail mechanism began in Windows 8." + Clang [`__builtin_verbose_trap`](https://clang.llvm.org/docs/LanguageExtensions.html#builtin-verbose-trap) + I measured `v[idx]` on x64 with `/O2`, and this reduced codegen size from 56 bytes to 29 bytes. Clang codegen was similarly improved. + In `<ranges>`, we need to avoid a Clang error: argument to `__builtin_verbose_trap` must be a pointer to a constant string
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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I pushed a commit to work around |
Zack Johnson (zacklj89)
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Stephan T. Lavavej (StephanTLavavej)
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🗺️ Overview
__fastfail:<intrin.h>. We generally try to avoid duplicating intrinsic declarations (due to calling convention madness) but in this one case I think it's fine. Because<yvals.h>is very central and special, moving the declaration into<intrin0.h>might still be overly impactful.FAST_FAIL_INVALID_ARGbecause there's no way we can drag in<winnt.h>.__builtin_verbose_trap:v[idx]on x64 with/O2:_invoke_watson()function call.<ranges>, we need to avoid a Clang error: "argument to__builtin_verbose_trapmust be a pointer to a constant string"./clr /std:c++20silent bad codegen with the__fastfailintrinsic".📜 Changelog
__fastfailintrinsic that was added in Windows 8, and the Clang__builtin_verbose_trapintrinsic.