[gcc r15-4462] middle-end: Fix VEC_PERM_EXPR lowering since relaxation of vector sizes

[Tamar Christina via Gcc-cvs]

https://gcc.gnu.org/g:55f898008ec8235897cf56c89f5599c3ec1bc963

commit r15-4462-g55f898008ec8235897cf56c89f5599c3ec1bc963
Author: Tamar Christina <tamar.christ...@arm.com>
Date:   Fri Oct 18 10:36:19 2024 +0100

    middle-end: Fix VEC_PERM_EXPR lowering since relaxation of vector sizes
    
    In GCC 14 VEC_PERM_EXPR was relaxed to be able to permute to a 2x larger 
vector
    than the size of the input vectors.  However various passes and 
transformations
    were not updated to account for this.
    
    I have patches in these area that I will be upstreaming with individual 
patches
    that expose them.
    
    This one is that vectlower tries to lower based on the size of the input 
vectors
    rather than the size of the output.  As a consequence it creates an invalid
    vector of half the size.
    
    Luckily we ICE because the resulting nunits doesn't match the vector size.
    
    gcc/ChangeLog:
    
            * tree-vect-generic.cc (lower_vec_perm): Use output vector size 
instead
            of input vector when determining output nunits.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/vec-perm-lower.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/vec-perm-lower.c | 16 ++++++++++++++++
 gcc/tree-vect-generic.cc              |  7 ++++---
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/vec-perm-lower.c 
b/gcc/testsuite/gcc.dg/vec-perm-lower.c
new file mode 100644
index 000000000000..da738fbeed80
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vec-perm-lower.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-fgimple -O2" } */
+
+typedef char v8qi __attribute__ ((vector_size (8)));
+typedef char v16qi __attribute__ ((vector_size (16)));
+
+v16qi __GIMPLE (ssa)
+foo (v8qi a, v8qi b)
+{
+  v16qi _5;
+
+  __BB(2):
+  _5 = __VEC_PERM (a, b, _Literal (unsigned char [[gnu::vector_size(16)]]) { 
_Literal (unsigned char) 0, _Literal (unsigned char) 16, _Literal (unsigned 
char) 1, _Literal (unsigned char) 17, _Literal (unsigned char) 2, _Literal 
(unsigned char) 18, _Literal (unsigned char) 3, _Literal (unsigned char) 19, 
_Literal (unsigned char) 4, _Literal (unsigned char) 20, _Literal (unsigned 
char) 5, _Literal (unsigned char) 21, _Literal (unsigned char) 6, _Literal 
(unsigned char) 22, _Literal (unsigned char) 7, _Literal (unsigned char) 23 });
+  return _5;
+
+}
diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index 3041fb8fcf23..f86f7eabb255 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -1500,6 +1500,7 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
   tree mask = gimple_assign_rhs3 (stmt);
   tree vec0 = gimple_assign_rhs1 (stmt);
   tree vec1 = gimple_assign_rhs2 (stmt);
+  tree res_vect_type = TREE_TYPE (gimple_assign_lhs (stmt));
   tree vect_type = TREE_TYPE (vec0);
   tree mask_type = TREE_TYPE (mask);
   tree vect_elt_type = TREE_TYPE (vect_type);
@@ -1512,7 +1513,7 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
   location_t loc = gimple_location (gsi_stmt (*gsi));
   unsigned i;
 
-  if (!TYPE_VECTOR_SUBPARTS (vect_type).is_constant (&elements))
+  if (!TYPE_VECTOR_SUBPARTS (res_vect_type).is_constant (&elements))
     return;
 
   if (TREE_CODE (mask) == SSA_NAME)
@@ -1672,9 +1673,9 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
     }
 
   if (constant_p)
-    constr = build_vector_from_ctor (vect_type, v);
+    constr = build_vector_from_ctor (res_vect_type, v);
   else
-    constr = build_constructor (vect_type, v);
+    constr = build_constructor (res_vect_type, v);
   gimple_assign_set_rhs_from_tree (gsi, constr);
   update_stmt (gsi_stmt (*gsi));
 }