[google] pessimize stack accounting during inlining

Xinliang David Li davidxl@google.com
Wed Jun 8 01:06:00 GMT 2011


Ok for google/main.   A good candidate patch for trunk too.

Thanks,

David

On Tue, Jun 7, 2011 at 4:29 PM, Mark Heffernan <meheff@google.com> wrote:
> This patch pessimizes stack accounting during inlining.  This enables
> setting a firm stack size limit (via parameters "large-stack-frame" and
> "large-stack-frame-growth").  Without this patch the inliner is overly
> optimistic about potential stack reuse resulting in actual stack frames much
> larger than the parameterized limits.
> Internal benchmarks show minor performance differences with non-fdo and
> lipo, but overall neutral.  Tested/bootstrapped on x86-64.
> Ok for google-main?
> Mark
>
> 2011-06-07  Mark Heffernan  <meheff@google.com>
>         * cgraph.h (cgraph_global_info): Remove field.
>         * ipa-inline.c (cgraph_clone_inlined_nodes): Change
>         stack frame computation.
>         (cgraph_check_inline_limits): Ditto.
>         (compute_inline_parameters): Remove dead initialization.
>
> Index: gcc/cgraph.h
> ===================================================================
> --- gcc/cgraph.h        (revision 174512)
> +++ gcc/cgraph.h        (working copy)
> @@ -136,8 +136,6 @@ struct GTY(()) cgraph_local_info {
>  struct GTY(()) cgraph_global_info {
>    /* Estimated stack frame consumption by the function.  */
>    HOST_WIDE_INT estimated_stack_size;
> -  /* Expected offset of the stack frame of inlined function.  */
> -  HOST_WIDE_INT stack_frame_offset;
>
>    /* For inline clones this points to the function they will be
>       inlined into.  */
> Index: gcc/ipa-inline.c
> ===================================================================
> --- gcc/ipa-inline.c    (revision 174512)
> +++ gcc/ipa-inline.c    (working copy)
> @@ -229,8 +229,6 @@ void
>  cgraph_clone_inlined_nodes (struct cgraph_edge *e, bool duplicate,
>                             bool update_original)
>  {
> -  HOST_WIDE_INT peak;
> -
>    if (duplicate)
>      {
>        /* We may eliminate the need for out-of-line copy to be output.
> @@ -279,13 +277,13 @@ cgraph_clone_inlined_nodes (struct cgrap
>      e->callee->global.inlined_to = e->caller->global.inlined_to;
>    else
>      e->callee->global.inlined_to = e->caller;
> -  e->callee->global.stack_frame_offset
> -    = e->caller->global.stack_frame_offset
> -      + inline_summary (e->caller)->estimated_self_stack_size;
> -  peak = e->callee->global.stack_frame_offset
> -      + inline_summary (e->callee)->estimated_self_stack_size;
> -  if (e->callee->global.inlined_to->global.estimated_stack_size < peak)
> -    e->callee->global.inlined_to->global.estimated_stack_size = peak;
> +
> +  /* Pessimistically assume no sharing of stack space.  That is, the
> +     frame size of a function is estimated as the original frame size
> +     plus the sum of the frame sizes of all inlined callees.  */
> +  e->callee->global.inlined_to->global.estimated_stack_size +=
> +    inline_summary (e->callee)->estimated_self_stack_size;
> +
>    cgraph_propagate_frequency (e->callee);
>
>    /* Recursively clone all bodies.  */
> @@ -430,8 +428,7 @@ cgraph_check_inline_limits (struct cgrap
>
>    stack_size_limit += stack_size_limit * PARAM_VALUE
> (PARAM_STACK_FRAME_GROWTH) / 100;
>
> -  inlined_stack = (to->global.stack_frame_offset
> -                  + inline_summary (to)->estimated_self_stack_size
> +  inlined_stack = (to->global.estimated_stack_size
>                    + what->global.estimated_stack_size);
>    if (inlined_stack  > stack_size_limit
>        && inlined_stack > PARAM_VALUE (PARAM_LARGE_STACK_FRAME))
> @@ -2064,7 +2061,6 @@ compute_inline_parameters (struct cgraph
>    self_stack_size = optimize ? estimated_stack_frame_size (node) : 0;
>    inline_summary (node)->estimated_self_stack_size = self_stack_size;
>    node->global.estimated_stack_size = self_stack_size;
> -  node->global.stack_frame_offset = 0;
>
>    /* Can this function be inlined at all?  */
>    node->local.inlinable = tree_inlinable_function_p (node->decl);
>



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