[ARM] Improve max_insns_skipped logic

Submitted by Wilco Dijkstra on April 20, 2017, 4:02 p.m.

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Message ID AM5PR0802MB2610082519E654AEDE937817831B0@AM5PR0802MB2610.eurprd08.prod.outlook.com
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Commit Message

Wilco Dijkstra April 20, 2017, 4:02 p.m.
ping


From: Wilco Dijkstra
Sent: 10 November 2016 17:19
To: GCC Patches
Cc: nd
Subject: [PATCH][ARM] Improve max_insns_skipped logic
    
Improve the logic when setting max_insns_skipped.  Limit the maximum size of IT
to MAX_INSN_PER_IT_BLOCK as otherwise multiple IT instructions are needed,
increasing codesize.  Given 4 works well for Thumb-2, use the same limit for ARM
for consistency. 

ChangeLog:
2016-11-04  Wilco Dijkstra  <wdijkstr@arm.com>

        * config/arm/arm.c (arm_option_params_internal): Improve setting of
        max_insns_skipped.
--

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diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index f046854e9665d54911616fc1c60fee407188f7d6..29e8d1d07d918fbb2a627a653510dfc8587ee01a 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -2901,20 +2901,12 @@  arm_option_params_internal (void)
       targetm.max_anchor_offset = TARGET_MAX_ANCHOR_OFFSET;
     }
 
-  if (optimize_size)
-    {
-      /* If optimizing for size, bump the number of instructions that we
-         are prepared to conditionally execute (even on a StrongARM).  */
-      max_insns_skipped = 6;
+  /* Increase the number of conditional instructions with -Os.  */
+  max_insns_skipped = optimize_size ? 4 : current_tune->max_insns_skipped;
 
-      /* For THUMB2, we limit the conditional sequence to one IT block.  */
-      if (TARGET_THUMB2)
-        max_insns_skipped = arm_restrict_it ? 1 : 4;
-    }
-  else
-    /* When -mrestrict-it is in use tone down the if-conversion.  */
-    max_insns_skipped = (TARGET_THUMB2 && arm_restrict_it)
-      ? 1 : current_tune->max_insns_skipped;
+  /* For THUMB2, we limit the conditional sequence to one IT block.  */
+  if (TARGET_THUMB2)
+    max_insns_skipped = MIN (max_insns_skipped, MAX_INSN_PER_IT_BLOCK);
 }
 
 /* True if -mflip-thumb should next add an attribute for the default