[gomp4, PR68977, Committed] Don't gimplify in ssa mode if seen_error in oacc_xform_loop

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

At r231739, there was an ICE when checking code generated by 
oacc_xform_loop, in case the source contained an error.

Due to seen_error (), gimplification during oacc_xform_loop bailed out, 
and an uninitialized var was introduced.  Because of gimplifying in ssa 
mode, that caused an ICE.

I can't reproduce this any longer, but I think the fix still makes 
sense. The patch makes sure oacc_xform_loop gimplifies in non-ssa mode 
if seen_error ().

Build on x86_64 with nvidia accelerator setup, tested libgomp and goacc.exp.

Committed to gomp-4_0-branch.

Thanks,
- Tom

Don't gimplify in ssa mode if seen_error in oacc_xform_loop

2016-01-13  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/68977
	* omp-low.c (oacc_xform_loop): Handle seen_error () == true.
---
 gcc/ChangeLog.gomp | 5 +++++
 gcc/omp-low.c      | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index c99f0b8..a6e3fe3 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -19105,7 +19105,12 @@ oacc_xform_loop (gcall *call)
        -> chunks=ceil (range/(chunksize*threads*step))
      striding=false,chunking=false
        -> chunk_size=ceil(range/(threads*step)),chunks=1  */
-  push_gimplify_context (true);
+
+  /* If seen_error (), we may introduce an uninitialized var due to
+     gimplification bailing out.  If we gimplify in ssa mode, that will cause an
+     ICE.  If we gimplify in non-ssa mode, then ssa updating will turn it into a
+     default definition, and we avoid the ICE.  */
+  push_gimplify_context (!seen_error ());
 
   switch (code)
     {