[PATCH] forwprop: Fix ICE when building an identity constructor [PR94700]

[Richard Sandiford]

This is really PR94683 part 2, handling the case in which the vector is
an identity and so doesn't need a VEC_PERM_EXPR.  I should have realised
at the time that the other arm of the "if" would need the same fix.

Tested on aarch64-linux-gnu, aarch64_be-elf and x86_64-linux-gnu.
OK to install?

Richard


2020-04-22  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        PR tree-optimization/94700
        * tree-ssa-forwprop.c (simplify_vector_constructor): When processing
        an identity constructor, use a VIEW_CONVERT_EXPR to handle mixtures
        of similarly-structured but distinct vector types.

gcc/testsuite/
        PR tree-optimization/94700
        * gcc.target/aarch64/sve/acle/general/pr94700.c: New test.
---
 .../aarch64/sve/acle/general/pr94700.c        | 28 +++++++++++++++++++
 gcc/tree-ssa-forwprop.c                       | 13 ++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr94700.c

diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index 1a50045b367..8ee5450b94c 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -2475,7 +2475,18 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
          orig[0] = gimple_assign_lhs (lowpart);
        }
       if (conv_code == ERROR_MARK)
-       gimple_assign_set_rhs_from_tree (gsi, orig[0]);
+       {
+         tree src_type = TREE_TYPE (orig[0]);
+         if (!useless_type_conversion_p (type, src_type))
+           {
+             gcc_assert (!targetm.compatible_vector_types_p (type, src_type));
+             tree rhs = build1 (VIEW_CONVERT_EXPR, type, orig[0]);
+             orig[0] = make_ssa_name (type);
+             gassign *assign = gimple_build_assign (orig[0], rhs);
+             gsi_insert_before (gsi, assign, GSI_SAME_STMT);
+           }
+         gimple_assign_set_rhs_from_tree (gsi, orig[0]);
+       }
       else
        gimple_assign_set_rhs_with_ops (gsi, conv_code, orig[0],
                                        NULL_TREE, NULL_TREE);
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr94700.c 
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr94700.c
new file mode 100644
index 00000000000..1feac60d8e9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr94700.c
@@ -0,0 +1,28 @@
+/* { dg-options "-O2 -msve-vector-bits=256" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include <arm_sve.h>
+
+typedef float v8sf __attribute__((vector_size(32)));
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+** test:
+**     fadd    z0\.s, p0/m, z0\.s, #1.0
+**     fdiv    z0\.s, p0/m, z0\.s, z1\.s
+**     ret
+*/
+svfloat32_t
+test (svbool_t pg, svfloat32_t x, svfloat32_t y)
+{
+  v8sf a = svadd_x (pg, x, 1);
+  v8sf b = { a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7] };
+  return svdiv_x (pg, b, y);
+}
+
+#ifdef __cplusplus
+}
+#endif