[x265] [PATCH 01/12] AArch64: Fix costCoeffNxN test on Apple Silicon

[Karam Singh]

Hello Hari,


Thank you for fixing the AARCH64 build issues. Can you please attach all
the patches?


Thanks & Regards,


Karam Singh
Senior Software (Video Codec) Engineer
MulticoreWare, India


On Tue, May 7, 2024 at 8:53 AM chen <chenm003 at 163.com> wrote:

> Hi Hari Limaye,
>
>
> Thank you fix AARCH64 build issues, these 12 patches looks good for me.
>
>
> Regards,
>
> Chen
>
> At 2024-05-03 05:19:36, "Hari Limaye" <hari.limaye at arm.com> wrote:
> >The assembly routine x265_costCoeffNxN_neon is buggy and produces an
> >incorrect result on Apple Silicon, causing the pixel testbench to fail
> >on these platforms.
> >
> >x265_costCoeffNxN assumes that parameter `int subPosBase`, the second
> >parameter of type `int` passed on the stack, is at position `sp + 8`;
> >this assumption is consistent with the AArch64 PCS, as arguments smaller
> >than 8 bytes are widened to 8 bytes (aapcs64 6.8.2 C.16).
> >However arm64e diverges from AAPCS64: 'Function arguments may consume
> >slots on the stack that are not multiples of 8 bytes'.
> >---
> > source/common/aarch64/asm.S        | 12 +++++++++++-
> > source/common/aarch64/pixel-util.S |  4 ++--
> > 2 files changed, 13 insertions(+), 3 deletions(-)
> >
> >diff --git a/source/common/aarch64/asm.S b/source/common/aarch64/asm.S
> >index ce0668103..742978631 100644
> >--- a/source/common/aarch64/asm.S
> >+++ b/source/common/aarch64/asm.S
> >@@ -72,6 +72,16 @@
> >
> > #define PFX_C(name)        JOIN(JOIN(JOIN(EXTERN_ASM, X265_NS), _), name)
> >
> >+// Alignment of stack arguments of size less than 8 bytes.
> >+#ifdef __APPLE__
> >+#define STACK_ARG_ALIGNMENT 4
> >+#else
> >+#define STACK_ARG_ALIGNMENT 8
> >+#endif
> >+
> >+// Get offset from SP of stack argument at index `idx`.
> >+#define STACK_ARG_OFFSET(idx) (idx * STACK_ARG_ALIGNMENT)
> >+
> > #ifdef __APPLE__
> > .macro endfunc
> > ELF .size \name, . - \name
> >@@ -184,4 +194,4 @@ ELF     .size   \name, . - \name
> >     vtrn            \t3, \t4, \s3, \s4
> > .endm
> >
> >-#endif
> >\ No newline at end of file
> >+#endif
> >diff --git a/source/common/aarch64/pixel-util.S b/source/common/aarch64/pixel-util.S
> >index 9b3c11504..378c6891c 100644
> >--- a/source/common/aarch64/pixel-util.S
> >+++ b/source/common/aarch64/pixel-util.S
> >@@ -2311,7 +2311,7 @@ endfunc
> > //    uint8_t *baseCtx,      // x6
> > //    int offset,            // x7
> > //    int scanPosSigOff,     // sp
> >-//    int subPosBase)        // sp + 8
> >+//    int subPosBase)        // sp + 8, or sp + 4 on APPLE
> > function PFX(costCoeffNxN_neon)
> >     // abs(coeff)
> >     add             x2, x2, x2
> >@@ -2410,7 +2410,7 @@ function PFX(costCoeffNxN_neon)
> >     add             x4, x4, x15
> >     str             h2, [x13]              // absCoeff[numNonZero] = tmpCoeff[blkPos]
> >
> >-    ldr             x9, [sp, #8]           // subPosBase
> >+    ldr             x9, [sp, #STACK_ARG_OFFSET(1)]           // subPosBase
> >     uxth            w9, w9
> >     cmp             w9, #0
> >     cset            x2, eq
> >--
> >2.42.1
> >
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