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Re: [lra] Cleanup the use of offmemok and don't count spilling cost for it

On 04/07/16 20:44, Vladimir Makarov wrote:
On 06/30/2016 01:22 PM, Jiong Wang wrote:

Here is the patch,
 From my understanding, "offmemok" is used to represent a memory operand
who's address we want to reload, and searching of it's reference location
seems confirmed my understanding as it's always used together with MEM_P check.

So this patch does the following modifications:

   * Only set offmemok to true if MEM_P is also true, as otherwise offmemok
     is not used.
   * Remove redundant MEM_P check which was used together with offmemok.
   * Avoid the addition of spilling cost if offmemok be true as an address
     calculation reload is not spilling.

bootstrap & gcc/g++ regression OK on x86_64/aarch64/arm.

OK for trunk?

Yes. The patch looks OK to me. Thank you for working on the solution, Jiong. As I wrote the code is very sensitive and any its change might affect some targets. Usually patches for this part of LRA can take a few iterations.

Thanks for the review Vlad.

As Bernd has concerns on merging MEM_P into offmemok. I committed the
following patch as r238010 which keeps the functional change but without
merging checks.

2016-07-05  Jiong Wang<>

  * lra-constraints.c (process_alt_operands): Don't add spilling cost
  for "offmemok".

diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index bf08dce..e9d3e43 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -2488,7 +2488,9 @@ process_alt_operands (int only_alternative)
 		 Code below increases the reject for both pseudo and non-pseudo
 		 spill.  */
-	      if (no_regs_p && !(REG_P (op) && hard_regno[nop] < 0))
+	      if (no_regs_p
+		  && !(MEM_P (op) && offmemok)
+		  && !(REG_P (op) && hard_regno[nop] < 0))
 		  if (lra_dump_file != NULL)

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