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pkg/highway: vendor and modify to remain all libc usage

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This commit is contained in:
Mitchell Hashimoto
2026-04-23 20:23:45 -07:00
parent bdb164a6e5
commit f3f9af6129
7 changed files with 210 additions and 93 deletions
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48
pkg/highway/src/cpp/targets.cpp
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@@ -1,35 +1,49 @@
#include <hwy/base.h>
#include <hwy/detect_targets.h>
#include <hwy/highway.h>
#include <hwy/targets.h>
// Vendored from google/highway hwy/targets.cc at commit:
// 66486a10623fa0d72fe91260f96c892e41aceb06
//
// Local modifications:
// - Dropped upstream CPU feature probing and platform-specific detection code
// in favor of Ghostty's Zig-provided ghostty_hwy_detect_targets().
// - Removed the HWY_WARN baseline-mismatch diagnostic path so this file does
// not depend on libc-backed formatting/logging.
// - Kept only the chosen-target bookkeeping and runtime dispatch state that
// Highway's HWY_DYNAMIC_DISPATCH machinery needs.
// - Added hwy_supported_targets() as a small C shim for Zig to query the final
// supported target mask.
//
// Why:
// - Ghostty wants a minimal vendored Highway runtime that avoids direct libc
// usage and lets Zig own target detection policy.
// - Narrowing this file to dispatch state makes the local fork easier to audit
// and maintain than carrying upstream's full platform detection surface.
#include "hwy/targets.h"
namespace hwy {
extern "C" int64_t ghostty_hwy_detect_targets();
// Vendored from Highway's hwy/targets.cc. Ghostty provides target detection in
// Zig, so this TU only retains the runtime dispatch/chosen-target state.
static int64_t DetectTargets() {
int64_t bits = HWY_SCALAR | HWY_EMU128;
#if (HWY_ARCH_X86 || HWY_ARCH_ARM) && HWY_HAVE_RUNTIME_DISPATCH
#if (HWY_ARCH_X86 || HWY_ARCH_ARM || HWY_ARCH_PPC || HWY_ARCH_S390X || \
HWY_ARCH_RISCV || HWY_ARCH_LOONGARCH) && \
HWY_HAVE_RUNTIME_DISPATCH
bits |= ghostty_hwy_detect_targets();
#else
bits |= HWY_ENABLED_BASELINE;
#endif
if ((bits & HWY_ENABLED_BASELINE) != HWY_ENABLED_BASELINE) {
const uint64_t bits_u = static_cast<uint64_t>(bits);
const uint64_t enabled = static_cast<uint64_t>(HWY_ENABLED_BASELINE);
HWY_WARN("CPU supports 0x%08x%08x, software requires 0x%08x%08x\n",
static_cast<uint32_t>(bits_u >> 32),
static_cast<uint32_t>(bits_u & 0xFFFFFFFF),
static_cast<uint32_t>(enabled >> 32),
static_cast<uint32_t>(enabled & 0xFFFFFFFF));
}
return bits;
}
// When running tests, this value can be set to the mocked supported targets
// mask. Only written to from a single thread before the test starts.
static int64_t supported_targets_for_test_ = 0;
// Mask of targets disabled at runtime with DisableTargets.
static int64_t supported_mask_ = LimitsMax<int64_t>();
HWY_DLLEXPORT void DisableTargets(int64_t disabled_targets) {
@@ -59,3 +73,7 @@ HWY_DLLEXPORT ChosenTarget& GetChosenTarget() {
}
} // namespace hwy
extern "C" int64_t hwy_supported_targets() {
return hwy::SupportedTargets();
}