[gcc r12-6962] veclower: Fix up -fcompare-debug issue in expand_vector_comparison [PR104307]

[gcc r12-6962] veclower: Fix up -fcompare-debug issue in expand_vector_comparison [PR104307]

[Jakub Jelinek]

https://gcc.gnu.org/g:e9bf6d6b0e1d67df6dcee042fbe37ab72c3a38d7

commit r12-6962-ge9bf6d6b0e1d67df6dcee042fbe37ab72c3a38d7
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Feb 1 16:02:54 2022 +0100

    veclower: Fix up -fcompare-debug issue in expand_vector_comparison [PR104307]
    
    The following testcase fails -fcompare-debug, because expand_vector_comparison
    since r11-1786-g1ac9258cca8030745d3c0b8f63186f0adf0ebc27 sets
    vec_cond_expr_only when it sees some use other than VEC_COND_EXPR that uses
    the lhs in its condition.
    Obviously we should ignore debug stmts when doing so, e.g. by not pushing
    them to uses.
    That would be a 2 liner change, but while looking at it, I'm also worried
    about VEC_COND_EXPRs that would use the lhs in more than one operand,
    like VEC_COND_EXPR <lhs, lhs, something> or VEC_COND_EXPR <lhs, something, lhs>
    (sure, they ought to be folded, but what if they weren't).  Because if
    something like that happens, then FOR_EACH_IMM_USE_FAST would push the same
    stmt multiple times and expand_vector_condition can return true even when
    it modifies it (for vector bool masking).
    And lastly, it seems quite wasteful to safe_push statements that will just
    cause vec_cond_expr_only = false; and break; in the second loop, both for
    cases like 1000 immediate non-VEC_COND_EXPR uses and for cases like
    999 VEC_COND_EXPRs with lhs in cond followed by a single non-VEC_COND_EXPR
    use.  So this patch only pushes VEC_COND_EXPRs there.
    
    2022-02-01  Jakub Jelinek  <jakub@redhat.com>
    
            PR middle-end/104307
            * tree-vect-generic.cc (expand_vector_comparison): Don't push debug
            stmts to uses vector, just set vec_cond_expr_only to false for
            non-VEC_COND_EXPRs instead of pushing them into uses.  Treat
            VEC_COND_EXPRs that use lhs not just in rhs1, but rhs2 or rhs3 too
            like non-VEC_COND_EXPRs.
    
            * gcc.target/i386/pr104307.c: New test.

Diff:
---
 gcc/testsuite/gcc.target/i386/pr104307.c |  6 +++++
 gcc/tree-vect-generic.cc                 | 38 +++++++++++++++++---------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/gcc/testsuite/gcc.target/i386/pr104307.c b/gcc/testsuite/gcc.target/i386/pr104307.c
new file mode 100644
index 00000000000..1301539851c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr104307.c
@@ -0,0 +1,6 @@
+/* PR middle-end/104307 */
+/* { dg-do compile } */
+/* { dg-require-effective-target int128 } */
+/* { dg-options "-O2 -mavx512f -fcompare-debug " } */
+
+#include "pr78669.c"
diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index f4fc7d16119..12a553ec8be 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -436,29 +436,31 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
      feeding a VEC_COND_EXPR statement.  */
   auto_vec<gimple *> uses;
   FOR_EACH_IMM_USE_FAST (use_p, iterator, lhs)
-    uses.safe_push (USE_STMT (use_p));
-
-  for (unsigned i = 0; i < uses.length (); i ++)
     {
-      gassign *use = dyn_cast<gassign *> (uses[i]);
-      if (use != NULL
+      gimple *use = USE_STMT (use_p);
+      if (is_gimple_debug (use))
+	continue;
+      if (is_gimple_assign (use)
 	  && gimple_assign_rhs_code (use) == VEC_COND_EXPR
-	  && gimple_assign_rhs1 (use) == lhs)
-	{
-	  gimple_stmt_iterator it = gsi_for_stmt (use);
-	  if (!expand_vector_condition (&it, dce_ssa_names))
-	    {
-	      vec_cond_expr_only = false;
-	      break;
-	    }
-	}
+	  && gimple_assign_rhs1 (use) == lhs
+	  && gimple_assign_rhs2 (use) != lhs
+	  && gimple_assign_rhs3 (use) != lhs)
+	uses.safe_push (use);
       else
-	{
-	  vec_cond_expr_only = false;
-	  break;
-	}
+	vec_cond_expr_only = false;
     }
 
+  if (vec_cond_expr_only)
+    for (gimple *use : uses)
+      {
+	gimple_stmt_iterator it = gsi_for_stmt (use);
+	if (!expand_vector_condition (&it, dce_ssa_names))
+	  {
+	    vec_cond_expr_only = false;
+	    break;
+	  }
+      }
+
   if (!uses.is_empty () && vec_cond_expr_only)
     return NULL_TREE;