From: Richard Biener <rguenther@suse.de>
Date: Wed, 28 Jun 2023 08:16:57 +0000 (+0200)
Subject: tree-optimization/110443 - prevent SLP splat of gathers
X-Git-Tag: basepoints/gcc-15~7983
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51c8cbc6bba387f953d9be48c4a4c8b657dd54a5;p=thirdparty%2Fgcc.git

tree-optimization/110443 - prevent SLP splat of gathers

The following prevents non-grouped load SLP in case the element
to splat is from a gather operation.  While it should be possible
to support this it is not similar to the single element interleaving
case I was trying to mimic here.

	PR tree-optimization/110443
	* tree-vect-slp.cc (vect_build_slp_tree_1): Reject non-grouped
	gather loads.

	* gcc.dg/torture/pr110443.c: New testcase.
---

diff --git a/gcc/testsuite/gcc.dg/torture/pr110443.c b/gcc/testsuite/gcc.dg/torture/pr110443.c
new file mode 100644
index 000000000000..61cf705869ce
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr110443.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+
+typedef struct {
+  float real;
+  float imag;
+} complex_t;
+extern unsigned char fftorder[];
+float *a52_imdct_256_data;
+int a52_imdct_256_i, a52_imdct_256_k;
+float a52_imdct_256_b_r;
+void a52_imdct_256()
+{
+  complex_t buf1[64];
+  a52_imdct_256_i = 0;
+  for (; a52_imdct_256_i < 64; a52_imdct_256_i++) {
+    a52_imdct_256_k = fftorder[a52_imdct_256_i];
+    buf1[a52_imdct_256_i].real = buf1[a52_imdct_256_i].imag =
+        a52_imdct_256_data[a52_imdct_256_k];
+  }
+  a52_imdct_256_b_r = buf1[0].real * buf1[0].imag;
+}
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 8cb1ac1f3194..355d078d66ef 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -1291,7 +1291,8 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
 		 vectorization.  For loop vectorization we can handle
 		 splats the same we handle single element interleaving.  */
 	      && (is_a <bb_vec_info> (vinfo)
-		  || stmt_info != first_stmt_info))
+		  || stmt_info != first_stmt_info
+		  || STMT_VINFO_GATHER_SCATTER_P (stmt_info)))
 	    {
 	      /* Not grouped load.  */
 	      if (dump_enabled_p ())