From 5b85ca5317f28a73eadf10d604d2a7421b84bed8 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Wed, 1 Nov 2023 10:01:09 +0100 Subject: [PATCH] avutil/x86/pixelutils: Empty MMX state in ff_pixelutils_sad_8x8_mmxext We currently mostly do not empty the MMX state in our MMX DSP functions; instead we only do so before code that might be using x87 code. This is a violation of the System V i386 ABI (and maybe of other ABIs, too): "The CPU shall be in x87 mode upon entry to a function. Therefore, every function that uses the MMX registers is required to issue an emms or femms instruction after using MMX registers, before returning or calling another function." (See 2.2.1 in [1]) This patch does not intend to change all these functions to abide by the ABI; it only does so for ff_pixelutils_sad_8x8_mmxext, as this function can by called by external users, because it is exported via the pixelutils API. Without this, the following fragment will assert (on x86/x64): uint8_t src1[8 * 8], src2[8 * 8]; av_pixelutils_sad_fn fn = av_pixelutils_get_sad_fn(3, 3, 0, NULL); fn(src1, 8, src2, 8); av_assert0_fpu(); [1]: https://raw.githubusercontent.com/wiki/hjl-tools/x86-psABI/intel386-psABI-1.1.pdf Signed-off-by: Andreas Rheinhardt --- libavutil/x86/pixelutils.asm | 1 + 1 file changed, 1 insertion(+) diff --git a/libavutil/x86/pixelutils.asm b/libavutil/x86/pixelutils.asm index fbe9b45971..0bcccb51f5 100644 --- a/libavutil/x86/pixelutils.asm +++ b/libavutil/x86/pixelutils.asm @@ -43,6 +43,7 @@ cglobal pixelutils_sad_8x8, 4,4,0, src1, stride1, src2, stride2 lea src2q, [src2q + 2*stride2q] %endrep movd eax, m2 + emms RET ;-------------------------------------------------------------------------------