MATCH: Fix infinite loop between `vec_cond(vec_cond(a,b,0), c, d)` and `a & b`

Match has a pattern which converts `vec_cond(vec_cond(a,b,0), c, d)`
into `vec_cond(a & b, c, d)` but since in this case a is a comparison
fold will change `a & b` back into `vec_cond(a,b,0)` which causes an
infinite loop.
The best way to fix this is to enable the patterns for vec_cond(*,vec_cond,*)
only for GIMPLE so we don't get an infinite loop for fold any more.

Note this is a latent bug since these patterns were added in r11-2577-g229752afe3156a
and was exposed by r14-3350-g47b833a9abe1 where now able to remove a VIEW_CONVERT_EXPR.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR middle-end/111699

gcc/ChangeLog:

	* match.pd ((c ? a : b) op d, (c ? a : b) op (c ? d : e),
	(v ? w : 0) ? a : b, c1 ? c2 ? a : b : b): Enable only for GIMPLE.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr111699-1.c: New test.

(cherry picked from commit e77428a9a336f57e3efe3eff95f2b491d7e9be14)

diff --git a/gcc/match.pd b/gcc/match.pd
index ae0304372148c20d7dccf3fc68ccf444c998007a..3651dd268149626548694b10b29a8bc0544df86a 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4551,6 +4551,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 /* (v ? w : 0) ? a : b is just (v & w) ? a : b
    Currently disabled after pass lvec because ARM understands
    VEC_COND_EXPR<v==w,-1,0> but not a plain v==w fed to BIT_IOR_EXPR.  */
+#if GIMPLE
+/* These can only be done in gimple as fold likes to convert:
+   (CMP) & N into (CMP) ? N : 0
+   and we try to match the same pattern again and again. */
 (simplify
  (vec_cond (vec_cond:s @0 @3 integer_zerop) @1 @2)
  (if (optimize_vectors_before_lowering_p () && types_match (@0, @3))
@@ -4585,6 +4589,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (vec_cond @0 @3 (vec_cond:s @1 @2 @3))
  (if (optimize_vectors_before_lowering_p () && types_match (@0, @1))
   (vec_cond (bit_and (bit_not @0) @1) @2 @3)))
+#endif
 
 /* Canonicalize mask ? { 0, ... } : { -1, ...} to ~mask if the mask
    types are compatible.  */

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr111699-1.c b/gcc/testsuite/gcc.c-torture/compile/pr111699-1.c
new file mode 100644 (file)
index 0000000..87b127e
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr111699-1.c
@@ -0,0 +1,7 @@
+typedef unsigned char __attribute__((__vector_size__ (8))) V;
+
+void
+foo (V *v)
+{
+  *v =  (V) 0x107B9A7FF >= (*v <= 0);
+}