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Fix the webp SSE4.1 kernels under the MSVC ABI #2

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Merged
beetlebugorg merged 1 commit into from
Aug 25, 2026
Merged

Fix the webp SSE4.1 kernels under the MSVC ABI #2

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15 changes: 13 additions & 2 deletions build/codecs.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -137,9 +137,20 @@ fn addWebp(b: *std.Build, mod: *std.Build.Module, target: std.Build.ResolvedTarg
switch (target.result.cpu.arch) {
.x86, .x86_64 => {
// SSE2 is baseline on x86_64 and the kernels guard themselves on
// 32-bit; SSE4.1 has to be asked for.
// 32-bit; SSE4.1 has to be asked for. It is asked for at the cc1
// level because zig resolves a C compile's cpu from the module
// target, and an -msse4.1 in cflags loses to it. The MSVC ABI is
// where that bites: clang defines _MSC_VER there, webp's cpu.h
// reads that as permission to use the SSE4.1 intrinsics (real
// MSVC needs no arch flag), and without the real features every
// kernel fails to compile. On the other ABIs nothing defines
// __SSE4_1__, so these units compile empty and the dispatcher
// stays on SSE2.
mod.addCSourceFiles(.{ .root = root, .files = &webp_dsp_sse2, .flags = &(base_flags ++ [_][]const u8{"-msse2"}) });
mod.addCSourceFiles(.{ .root = root, .files = &webp_dsp_sse41, .flags = &(base_flags ++ [_][]const u8{"-msse4.1"}) });
mod.addCSourceFiles(.{ .root = root, .files = &webp_dsp_sse41, .flags = &(base_flags ++ [_][]const u8{
"-Xclang", "-target-feature", "-Xclang", "+ssse3",
"-Xclang", "-target-feature", "-Xclang", "+sse4.1",
}) });
},
.aarch64, .aarch64_be => {
mod.addCSourceFiles(.{ .root = root, .files = &webp_dsp_neon, .flags = &base_flags });
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