[PR65637][PATCH][2/3] Fix inner loop phi in expand_omp_for_static_chunk

[Tom de Vries <Tom_deVries@mentor.com>]

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On 15-04-15 15:10, Tom de Vries wrote:
> Hi,
>
> This patch series fixes PR65637.
>
> Currently, ssa-handling code in expand_omp_for_static_chunk is dead and not
> exercised by testing.
>
> Ssa-handling code in omp-low.c is only triggered by pass_parallelize_loops, and
> that pass doesn't specify a chunk size on the GIMPLE_OMP_FOR it constructs, so
> that only exercises the expand_omp_for_static_nochunk path.
>
> Using the attached trigger patch, we excercise the ssa-handling code in
> expand_omp_for_static_chunk. The following patch series fixes the problems in
> the ssa-handling code that we encounter.
>
> 1. Fix gcc_assert in expand_omp_for_static_chunk
> 2. Fix inner loop phi in expand_omp_for_static_chunk
> 3. Handle 2 preds for fin_bb in expand_omp_for_static_chunk
>
> The patch series has been bootstrapped and reg-tested on x86_64 together with
> attached trigger patch.
>
> I'll post the patches from the patch series individually, in response to this
> email.
>

This patch fixes an libgomp.c/autopar-1.c execution failure.

For autopar-1.c, the original loop has a loop phi:
...
# s.5_20 = PHI <s.5_12(4), 0.0(20)>
...

After expand_omp_for_static_chunk, there's an inner and an outer loop. The outer
loop phi is:
...
# s.5_11 = PHI <0.0(15), s.5_12(21)>
...

and the inner loop phi is:
...
# s.5_20 = PHI <s.5_12(4), 0.0(20)>
...

The inner loop phi should not have 0.0 as argument, but the result of the outer
loop phi, like this:
...
# s.5_20 = PHI <s.5_12(4), s.5_11(20)>
...

This patch fixes the inner loop phi, and allows the autopar-1.c execution test
to pass.

OK for trunk?

Thanks,
- Tom


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Fix inner loop phi in expand_omp_for_static_chunk

2015-04-15  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/65637
	* omp-low.c (find_phi_with_arg_on_edge): New function.
	(expand_omp_for_static_chunk): Fix inner loop phi.

---
 gcc/omp-low.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index f7b9d11..62cbed0 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -6844,6 +6844,22 @@ expand_omp_for_static_nochunk (struct omp_region *region,
     }
 }
 
+static gphi *
+find_phi_with_arg_on_edge (tree arg, edge e)
+{
+  basic_block bb = e->dest;
+
+  for (gphi_iterator gpi = gsi_start_phis (bb);
+       !gsi_end_p (gpi);
+       gsi_next (&gpi))
+    {
+      gphi *phi = gpi.phi ();
+      if (PHI_ARG_DEF_FROM_EDGE (phi, e) == arg)
+	return phi;
+    }
+
+  return NULL;
+}
 
 /* A subroutine of expand_omp_for.  Generate code for a parallel
    loop with static schedule and a specified chunk size.  Given
@@ -7272,7 +7288,14 @@ expand_omp_for_static_chunk (struct omp_region *region,
 	    t = vextra;
 	  add_phi_arg (nphi, t, ene, locus);
 	  locus = redirect_edge_var_map_location (vm);
-	  add_phi_arg (nphi, redirect_edge_var_map_def (vm), re, locus);
+	  tree back_arg = redirect_edge_var_map_def (vm);
+	  add_phi_arg (nphi, back_arg, re, locus);
+	  gphi *inner_loop_phi
+	    = find_phi_with_arg_on_edge (back_arg,
+					 find_edge (cont_bb, body_bb));
+	  gcc_assert (inner_loop_phi != NULL);
+	  add_phi_arg (inner_loop_phi, gimple_phi_result (nphi),
+		       find_edge (seq_start_bb, body_bb), locus);
 	}
       gcc_assert (gsi_end_p (psi) && (head == NULL || i == head->length ()));
       redirect_edge_var_map_clear (re);
-- 
1.9.1