match.pd: Avoid simplification into invalid BIT_FIELD_REFs [PR112673]

The following testcase is lowered by the bitint lowering pass, then
vectorizer vectorizes one of the loops in it, so we have
  vect__18.6_34 = VIEW_CONVERT_EXPR<vector(4) unsigned long>(x_35(D));
  _8 = BIT_FIELD_REF <vect__18.6_34, 64, 0>;
...
  _18 = BIT_FIELD_REF <vect__18.6_34, 64, 64>;
etc. where x_35(D) is _BitInt(256) argument.  That is valid BIT_FIELD_REF,
the first argument is a vector and it extracts the vector elements from it.
Then comes forwprop4 and simplifies that using match.pd into
  _8 = (unsigned long) x_35(D);
...
  _18 = BIT_FIELD_REF <x_35(D), 64, 64>;
and tree-cfg verification ICEs on the latter (though, even the first cast
is kind of undesirable after bitint lowering, we want large/huge bitints
lowered).  The ICE is because if BIT_FIELD_REFs first argument has
INTEGRAL_TYPE_P, we require type_has_mode_precision_p, but that is not the
case of _BitInt(256), it has BLKmode.

The following patch fixes it by doing the BIT_FIELD_REF with VCE to
BIT_FIELD_REF simplification only if the result is valid.

2023-11-24  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/112673
	* match.pd (bit_field_ref (vce @0) -> bit_field_ref @0): Only simplify
	if either @0 doesn't have scalar integral type or if it has mode
	precision.

	* gcc.dg/pr112673.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index b30de36e83623a158badd14160e262ca4211ceae..61e5d3441f4890f9678b17599184452d71a39265 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -8285,7 +8285,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
 (simplify
  (BIT_FIELD_REF (view_convert @0) @1 @2)
- (BIT_FIELD_REF @0 @1 @2))
+ (if (! INTEGRAL_TYPE_P (TREE_TYPE (@0))
+      || type_has_mode_precision_p (TREE_TYPE (@0)))
+  (BIT_FIELD_REF @0 @1 @2)))
 
 (simplify
  (BIT_FIELD_REF @0 @1 integer_zerop)

diff --git a/gcc/testsuite/gcc.dg/pr112673.c b/gcc/testsuite/gcc.dg/pr112673.c
new file mode 100644 (file)
index 0000000..531f277
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr112673.c
@@ -0,0 +1,10 @@
+/* PR tree-optimization/112673 */
+/* { dg-do compile { target bitint575 } } */
+/* { dg-options "-O3" } */
+/* { dg-additional-options "-mavx2" { target i?86-*-* x86_64-*-* } } */
+
+int
+foo (_BitInt(256) x)
+{
+  return __builtin_ctzg ((unsigned _BitInt(512)) x);
+}