[gcc r13-5651] middle-end/108625 - wrong folding due to misinterpreted !

[gcc r13-5651] middle-end/108625 - wrong folding due to misinterpreted !

[Richard Biener]

https://gcc.gnu.org/g:605d1297b91c2c7c23ccfe669e66dda5791d1f55

commit r13-5651-g605d1297b91c2c7c23ccfe669e66dda5791d1f55
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Feb 2 11:09:26 2023 +0100

    middle-end/108625 - wrong folding due to misinterpreted !
    
    The following fixes a problem with ! handling in genmatch which isn't
    conservative enough when intermediate simplifications push to the
    sequence but the final operation appears to just pick an existing
    (but in this case newly defined in the sequence) operand.  The easiest
    fix is to disallow adding to the sequence when processing !.
    
            PR middle-end/108625
            * genmatch.cc (expr::gen_transform): Also disallow resimplification
            from pushing to lseq with force_leaf.
            (dt_simplify::gen_1): Likewise.
    
            * gcc.dg/pr108625.c: New testcase.

Diff:
---
 gcc/genmatch.cc                 |  6 ++++--
 gcc/testsuite/gcc.dg/pr108625.c | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/gcc/genmatch.cc b/gcc/genmatch.cc
index e147ab9db7a..43bd0212d0e 100644
--- a/gcc/genmatch.cc
+++ b/gcc/genmatch.cc
@@ -2541,7 +2541,8 @@ expr::gen_transform (FILE *f, int indent, const char *dest, bool gimple,
       for (unsigned i = 0; i < ops.length (); ++i)
 	fprintf (f, ", _o%d[%u]", depth, i);
       fprintf (f, ");\n");
-      fprintf_indent (f, indent, "tem_op.resimplify (lseq, valueize);\n");
+      fprintf_indent (f, indent, "tem_op.resimplify (%s, valueize);\n",
+		      !force_leaf ? "lseq" : "NULL");
       fprintf_indent (f, indent,
 		      "_r%d = maybe_push_res_to_seq (&tem_op, %s);\n", depth,
 		      !force_leaf ? "lseq" : "NULL");
@@ -3451,7 +3452,8 @@ dt_simplify::gen_1 (FILE *f, int indent, bool gimple, operand *result)
 	  if (!is_predicate)
 	    {
 	      fprintf_indent (f, indent,
-			      "res_op->resimplify (lseq, valueize);\n");
+			      "res_op->resimplify (%s, valueize);\n",
+			      !e->force_leaf ? "lseq" : "NULL");
 	      if (e->force_leaf)
 		fprintf_indent (f, indent,
 				"if (!maybe_push_res_to_seq (res_op, NULL)) "
diff --git a/gcc/testsuite/gcc.dg/pr108625.c b/gcc/testsuite/gcc.dg/pr108625.c
new file mode 100644
index 00000000000..03fc2889c4f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108625.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-forwprop1 -fdump-tree-optimized" } */
+
+unsigned char foo(int x)
+{
+  int t = -x;
+  unsigned char t1 = t;
+  unsigned char t2 = t;
+  /* We may not rewrite this as (unsigned char)(t - x).  */
+  return t1 + t2;
+}
+
+/* { dg-final { scan-tree-dump-times "x_" 1 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times "x_" 1 "optimized" } } */