[PATCH] rs6000: Retry tbegin. instructions that can fail intermittently

[Peter Bergner via Gcc-patches]

The HTM tbegin. instruction can fail intermittently due to many reasons.
This can lead to the htm-1.c testsuite test case FAILing from time to time.
The solution is to allow retrying the instruction a few times before aborting.

Bill has seen this fail a 1-2 times per 10000 runs.  With the change below, I
haven't seen the test case fail in over 1 million runs.

Ok for trunk and backports to the release branches?

Peter


gcc/testsuite/
        * gcc.target/powerpc/htm-1.c: Retry intermittent failing tbegins.

diff --git a/gcc/testsuite/gcc.target/powerpc/htm-1.c 
b/gcc/testsuite/gcc.target/powerpc/htm-1.c
index f27e32ca281..399a7ec8812 100644
--- a/gcc/testsuite/gcc.target/powerpc/htm-1.c
+++ b/gcc/testsuite/gcc.target/powerpc/htm-1.c
@@ -12,14 +12,21 @@ main (void)
 {
   long i;
   unsigned long mask = 0;
+  unsigned long retry_count = 0;
 
 repeat:
   if (__builtin_tbegin (0))
     {
       mask++;
+      retry_count = 0;
     }
   else
-    abort();
+    {
+      /* Retry a limited number of times before aborting.  */
+      if (retry_count++ < 10)
+       goto repeat;
+      abort ();
+    }
 
   if (mask == 1)
     {