[PATCH] Fix ICE in Tree-VRP

[Eric Botcazou]

Hi,

The compiler ICEs at -O2 on the attached testcase, a regression from 3.x:

eric@linux:~/build/gcc/native32> gcc/xgcc -Bgcc -S -O2 tti0.adb -Igcc/ada/rts
+===========================GNAT BUG DETECTED==============================+
| 4.2.0 20060503 (experimental) (i586-suse-linux-gnu) GCC error:           |
| in set_value_range, at tree-vrp.c:157                                    |
| Error detected at tti0.adb:39:4                                          |

The relevant statement is:

   if Least_Significant < Most_Significant then
      Least_Significant := Most_Significant;
   end if;

Both Least_Significant and Most_Significant are Boolean and VRP computes that 
Least_Significant is equal to True (1).  When the pass is extracting the 
range from the associated ASSERT expression, it builds a range of the form 
[MIN+1, MAX] but here we have MIN == MAX so set_value_range aborts.

The proposed fix is to set the range to VARYING in this case.  I don't think 
something more sophisticated would be worthwhile as all should be optimized 
away in the branch.

Tested on x86_64-suse-linux.  OK for mainline and 4.1 branch?


2006-05-05  Eric Botcazou  <ebotcazou@adacore.com>

	* tree-vrp.c (extract_range_from_assert): Set the range to VARYING
	for LT and GT if the computed range is effectively empty.


-- 
Eric Botcazou
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