[PATCH] tree-optimization/101505 - properly determine stmt precision for PHIs

[Richard Biener]

Loop vectorization pattern recog fails to walk PHIs when determining
stmt precisions.  This fails to recognize non-mask uses for bools
in PHIs and outer loop vectorization.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2021-07-19  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/101505
        * tree-vect-patterns.c (vect_determine_precisions): Walk
        PHIs also for loop vectorization.

        * gcc.dg/vect/pr101505.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/pr101505.c | 16 ++++++++++++++++
 gcc/tree-vect-patterns.c             | 14 ++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr101505.c

diff --git a/gcc/testsuite/gcc.dg/vect/pr101505.c 
b/gcc/testsuite/gcc.dg/vect/pr101505.c
new file mode 100644
index 00000000000..e2b8945a5cc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr101505.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O1" } */
+
+int n2;
+
+__attribute__ ((simd)) char
+w7 (void)
+{
+  short int xb = n2;
+  int qp;
+
+  for (qp = 0; qp < 2; ++qp)
+    xb = xb < 1;
+
+  return xb;
+}
diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index c2494446183..44f6c9b2bd6 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -5355,6 +5355,13 @@ vect_determine_precisions (vec_info *vinfo)
       for (unsigned int i = 0; i < nbbs; i++)
        {
          basic_block bb = bbs[i];
+         for (auto gsi = gsi_start_phis (bb);
+              !gsi_end_p (gsi); gsi_next (&gsi))
+           {
+             stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi.phi ());
+             if (stmt_info)
+               vect_determine_mask_precision (vinfo, stmt_info);
+           }
          for (auto si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
            if (!is_gimple_debug (gsi_stmt (si)))
              vect_determine_mask_precision
@@ -5368,6 +5375,13 @@ vect_determine_precisions (vec_info *vinfo)
            if (!is_gimple_debug (gsi_stmt (si)))
              vect_determine_stmt_precisions
                (vinfo, vinfo->lookup_stmt (gsi_stmt (si)));
+         for (auto gsi = gsi_start_phis (bb);
+              !gsi_end_p (gsi); gsi_next (&gsi))
+           {
+             stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi.phi ());
+             if (stmt_info)
+               vect_determine_stmt_precisions (vinfo, stmt_info);
+           }
        }
     }
   else
-- 
2.26.2