From: Alex Coplan <alex.coplan@arm.com>
Date: Tue, 9 Sep 2025 11:57:14 +0000 (+0100)
Subject: match.pd: Add missing type check to reduc(ctor) pattern [PR121772]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a7a9b7badc0ba95b510c7e61da6439fca78e31d3;p=thirdparty%2Fgcc.git

match.pd: Add missing type check to reduc(ctor) pattern [PR121772]

In this PR we have a reduction of a vector constructor, where the
type of the constructor is int16x8_t and the elements are int16x4_t;
i.e. it is representing a concatenation of two vectors.

This triggers a match.pd pattern which looks like it was written to
handle reductions of vector constructors where the elements of the ctor
are scalars, not vectors.  There is no type check to enforce this
property, which leads to the pattern replacing a reduction to scalar
with an int16x4_t vector in this case, which of course is a type error,
leading to an invalid GIMPLE ICE.

This patch adds a type check to the pattern, only going ahead with the
transformation if the element type of the ctor matches that of the
reduction.

gcc/ChangeLog:

	PR tree-optimization/121772
	* match.pd: Add type check to reduc(ctor) pattern.

gcc/testsuite/ChangeLog:

	PR tree-optimization/121772
	* gcc.target/aarch64/torture/pr121772.c: New test.
---

diff --git a/gcc/match.pd b/gcc/match.pd
index dbbb7b51275..8107ee6ec83 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -11085,6 +11085,7 @@ and,
 			 ? gimple_assign_rhs1 (SSA_NAME_DEF_STMT (@0)) : @0);
 	    tree elt = ctor_single_nonzero_element (ctor); }
       (if (elt
+	   && types_match (type, TREE_TYPE (elt))
 	   && !HONOR_SNANS (type)
 	   && !HONOR_SIGNED_ZEROS (type))
 	{ elt; }))))
diff --git a/gcc/testsuite/gcc.target/aarch64/torture/pr121772.c b/gcc/testsuite/gcc.target/aarch64/torture/pr121772.c
new file mode 100644
index 00000000000..3b4cf4d7d18
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/torture/pr121772.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+#include <arm_neon.h>
+int16_t f(int16x4_t b) {
+  return vaddvq_s16(vcombine_s16(b, vdup_n_s16 (0)));
+}