Re: using scratchpads to enhance RTL-level if-conversion: revised patch

[Sebastian Pop <sebpop at gmail dot com>]

Hi Abe,

could you please avoid double negations, and
please use early returns rather than huge right indentations:

+  if (! not_a_scratchpad_candidate)
+  {
+    if (MEM_SIZE_KNOWN_P (orig_x))
+    {
+      const size_t size_of_MEM = MEM_SIZE (orig_x);
+
+      if (size_of_MEM <= SCRATCHPAD_MAX_SIZE)
+      {
[...]
+      }
+    }
+  }
+  return FALSE;

Just rewrite as:

if (not_a_scratchpad_candidate
    || !MEM_SIZE_KNOWN_P (orig_x))
  return FALSE;

const size_t size_of_MEM = MEM_SIZE (orig_x);
if (size_of_MEM > SCRATCHPAD_MAX_SIZE)
  return FALSE;

That will save 3 levels of indent.

Also some of your braces do not seem to be correctly placed.
Please use clang-format on your patch to solve the indentation issues.

Thanks,
Sebastian


On Wed, Oct 7, 2015 at 6:29 PM, Abe <abe_skolnik@yahoo.com> wrote:
> Dear all,
>
> Attached please find my revised patch to the RTL if converter.  This patch
> enables the
> if-conversion of half-hammocks with a store in them that the internal GCC
> machinery
> otherwise considers too hazardous to if-convert.  This is made safe by using
> the
> "scratchpad" technique, i.e. throwing away the store into a safe location
> where nothing
> of any importance is currently stored.  The scratchpads are allocated in the
> stack frame.
>
> Here is an example of code which is newly converted with this patch,
> at least when targeting AArch64:
>
>   int A[10];
>
>   void half_hammock() {
>     if (A[0])
>       A[1] = 2;
>   }
>
>
> Both tested against trunk and bootstrapped OK with defaults* on
> AMD64-AKA-"x86_64" GNU/Linux.
>
> '*': [except for "--prefix"]
>
>
> I`m sending the patch as an attachment to avoid it
> being corrupted/reformatted by any e-mail troubles.
>
> I look forward to your feedback.
>
> Regards,
>
> Abe
>