[patch] Stop gengtype from emitting empty loops

[Steven Bosscher <stevenb dot gcc at gmail dot com>]

Hello,

For scalar fields or skipped fields, gengtype produces empty loops.
This patch checks for that case and breaks out if an empty loop body
is detected:

--- gtype-desc.c.orig   2012-07-24 01:57:42.830007515 -0700
+++ gtype-desc.c        2012-07-24 02:10:14.530007515 -0700
@@ -89,6 +89,7 @@
         {
           size_t i0;
           for (i0 = 0; i0 != l0; i0++) {
+            break;
           }
         }
       }

This probably helps only for -O0 builds, but I do a lot of those.
Compile time for powerpc64-unknown-linux-gnu/bits/extc++.h.gch/O2g.gch
drops from "user 2m29.112s" to "user 0m30.208s" for a -O0 built
cc1plus.

Bootstrapped&tested on powerpc64-unknown-linux-gnu. OK?

Ciao!
Steven

Attachment: gengtype_O0_speedup.diff
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