[FFmpeg-devel] [PATCH 1/4] x86inc: Support arbitrary stack alignments
Dewangan, Hitesh Kumar
hitesh.dewangan at pearson.com
Mon Aug 3 16:54:01 CEST 2015
Hi all,
Can you please remove me from this group.
Thanks,
Hitesh
On Aug 3, 2015 2:14 AM, "Henrik Gramner" <henrik at gramner.com> wrote:
> Change ALLOC_STACK to always align the stack before allocating stack space
> for
> consistency. Previously alignment would occur either before or after
> allocating
> stack space depending on whether manual alignment was required or not.
> ---
> libavcodec/x86/h264_deblock.asm | 4 +--
> libavutil/x86/x86inc.asm | 62
> ++++++++++++++++++++++++++---------------
> 2 files changed, 42 insertions(+), 24 deletions(-)
>
> diff --git a/libavcodec/x86/h264_deblock.asm
> b/libavcodec/x86/h264_deblock.asm
> index 14c8205..5151f3c 100644
> --- a/libavcodec/x86/h264_deblock.asm
> +++ b/libavcodec/x86/h264_deblock.asm
> @@ -446,13 +446,13 @@ cglobal deblock_%1_luma_8, 5,5,8,2*%2
> ; int8_t *tc0)
>
> ;-----------------------------------------------------------------------------
> INIT_MMX cpuname
> -cglobal deblock_h_luma_8, 0,5,8,0x60+HAVE_ALIGNED_STACK*12
> +cglobal deblock_h_luma_8, 0,5,8,0x60+12
> mov r0, r0mp
> mov r3, r1m
> lea r4, [r3*3]
> sub r0, 4
> lea r1, [r0+r4]
> -%define pix_tmp esp+12*HAVE_ALIGNED_STACK
> +%define pix_tmp esp+12
>
> ; transpose 6x16 -> tmp space
> TRANSPOSE6x8_MEM PASS8ROWS(r0, r1, r3, r4), pix_tmp
> diff --git a/libavutil/x86/x86inc.asm b/libavutil/x86/x86inc.asm
> index 12779f5..e176715 100644
> --- a/libavutil/x86/x86inc.asm
> +++ b/libavutil/x86/x86inc.asm
> @@ -42,6 +42,17 @@
> %define public_prefix private_prefix
> %endif
>
> +%if HAVE_ALIGNED_STACK
> + %define STACK_ALIGNMENT 16
> +%endif
> +%ifndef STACK_ALIGNMENT
> + %if ARCH_X86_64
> + %define STACK_ALIGNMENT 16
> + %else
> + %define STACK_ALIGNMENT 4
> + %endif
> +%endif
> +
> %define WIN64 0
> %define UNIX64 0
> %if ARCH_X86_64
> @@ -108,8 +119,9 @@
> ; %1 = number of arguments. loads them from stack if needed.
> ; %2 = number of registers used. pushes callee-saved regs if needed.
> ; %3 = number of xmm registers used. pushes callee-saved xmm regs if
> needed.
> -; %4 = (optional) stack size to be allocated. If not aligned (x86-32 ICC
> 10.x,
> -; MSVC or YMM), the stack will be manually aligned (to 16 or 32
> bytes),
> +; %4 = (optional) stack size to be allocated. The stack will be aligned
> before
> +; allocating the specified stack size. If the required stack
> alignment is
> +; larger than the known stack alignment the stack will be manually
> aligned
> ; and an extra register will be allocated to hold the original stack
> ; pointer (to not invalidate r0m etc.). To prevent the use of an
> extra
> ; register as stack pointer, request a negative stack size.
> @@ -117,8 +129,10 @@
> ; PROLOGUE can also be invoked by adding the same options to cglobal
>
> ; e.g.
> -; cglobal foo, 2,3,0, dst, src, tmp
> -; declares a function (foo), taking two args (dst and src) and one local
> variable (tmp)
> +; cglobal foo, 2,3,7,0x40, dst, src, tmp
> +; declares a function (foo) that automatically loads two arguments (dst
> and
> +; src) into registers, uses one additional register (tmp) plus 7 vector
> +; registers (m0-m6) and allocates 0x40 bytes of stack space.
>
> ; TODO Some functions can use some args directly from the stack. If
> they're the
> ; last args then you can just not declare them, but if they're in the
> middle
> @@ -319,26 +333,28 @@ DECLARE_REG_TMP_SIZE
> 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14
> %assign n_arg_names %0
> %endmacro
>
> +%define required_stack_alignment ((mmsize + 15) & ~15)
> +
> %macro ALLOC_STACK 1-2 0 ; stack_size, n_xmm_regs (for win64 only)
> %ifnum %1
> %if %1 != 0
> - %assign %%stack_alignment ((mmsize + 15) & ~15)
> + %assign %%pad 0
> %assign stack_size %1
> %if stack_size < 0
> %assign stack_size -stack_size
> %endif
> - %assign stack_size_padded stack_size
> %if WIN64
> - %assign stack_size_padded stack_size_padded + 32 ;
> reserve 32 bytes for shadow space
> + %assign %%pad %%pad + 32 ; shadow space
> %if mmsize != 8
> %assign xmm_regs_used %2
> %if xmm_regs_used > 8
> - %assign stack_size_padded stack_size_padded +
> (xmm_regs_used-8)*16
> + %assign %%pad %%pad + (xmm_regs_used-8)*16 ;
> callee-saved xmm registers
> %endif
> %endif
> %endif
> - %if mmsize <= 16 && HAVE_ALIGNED_STACK
> - %assign stack_size_padded stack_size_padded +
> %%stack_alignment - gprsize - (stack_offset & (%%stack_alignment - 1))
> + %if required_stack_alignment <= STACK_ALIGNMENT
> + ; maintain the current stack alignment
> + %assign stack_size_padded stack_size + %%pad +
> ((-%%pad-stack_offset-gprsize) & (STACK_ALIGNMENT-1))
> SUB rsp, stack_size_padded
> %else
> %assign %%reg_num (regs_used - 1)
> @@ -347,17 +363,17 @@ DECLARE_REG_TMP_SIZE
> 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14
> ; it, i.e. in [rsp+stack_size_padded], so we can restore
> the
> ; stack in a single instruction (i.e. mov rsp, rstk or mov
> ; rsp, [rsp+stack_size_padded])
> - mov rstk, rsp
> %if %1 < 0 ; need to store rsp on stack
> - sub rsp, gprsize+stack_size_padded
> - and rsp, ~(%%stack_alignment-1)
> - %xdefine rstkm [rsp+stack_size_padded]
> - mov rstkm, rstk
> + %xdefine rstkm [rsp + stack_size + %%pad]
> + %assign %%pad %%pad + gprsize
> %else ; can keep rsp in rstk during whole function
> - sub rsp, stack_size_padded
> - and rsp, ~(%%stack_alignment-1)
> %xdefine rstkm rstk
> %endif
> + %assign stack_size_padded stack_size + ((%%pad +
> required_stack_alignment-1) & ~(required_stack_alignment-1))
> + mov rstk, rsp
> + and rsp, ~(required_stack_alignment-1)
> + sub rsp, stack_size_padded
> + movifnidn rstkm, rstk
> %endif
> WIN64_PUSH_XMM
> %endif
> @@ -366,7 +382,7 @@ DECLARE_REG_TMP_SIZE 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14
>
> %macro SETUP_STACK_POINTER 1
> %ifnum %1
> - %if %1 != 0 && (HAVE_ALIGNED_STACK == 0 || mmsize == 32)
> + %if %1 != 0 && required_stack_alignment > STACK_ALIGNMENT
> %if %1 > 0
> %assign regs_used (regs_used + 1)
> %elif ARCH_X86_64 && regs_used == num_args && num_args <= 4 +
> UNIX64 * 2
> @@ -440,7 +456,9 @@ DECLARE_REG 14, R15, 120
> %assign xmm_regs_used %1
> ASSERT xmm_regs_used <= 16
> %if xmm_regs_used > 8
> - %assign stack_size_padded (xmm_regs_used-8)*16 +
> (~stack_offset&8) + 32
> + ; Allocate stack space for callee-saved xmm registers plus shadow
> space and align the stack.
> + %assign %%pad (xmm_regs_used-8)*16 + 32
> + %assign stack_size_padded %%pad + ((-%%pad-stack_offset-gprsize)
> & (STACK_ALIGNMENT-1))
> SUB rsp, stack_size_padded
> %endif
> WIN64_PUSH_XMM
> @@ -456,7 +474,7 @@ DECLARE_REG 14, R15, 120
> %endrep
> %endif
> %if stack_size_padded > 0
> - %if stack_size > 0 && (mmsize == 32 || HAVE_ALIGNED_STACK == 0)
> + %if stack_size > 0 && required_stack_alignment > STACK_ALIGNMENT
> mov rsp, rstkm
> %else
> add %1, stack_size_padded
> @@ -522,7 +540,7 @@ DECLARE_REG 14, R15, 72
>
> %macro RET 0
> %if stack_size_padded > 0
> -%if mmsize == 32 || HAVE_ALIGNED_STACK == 0
> +%if required_stack_alignment > STACK_ALIGNMENT
> mov rsp, rstkm
> %else
> add rsp, stack_size_padded
> @@ -578,7 +596,7 @@ DECLARE_ARG 7, 8, 9, 10, 11, 12, 13, 14
>
> %macro RET 0
> %if stack_size_padded > 0
> -%if mmsize == 32 || HAVE_ALIGNED_STACK == 0
> +%if required_stack_alignment > STACK_ALIGNMENT
> mov rsp, rstkm
> %else
> add rsp, stack_size_padded
> --
> 1.8.3.2
>
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