The last match.pd update for double-conversion folding didn't handle
the case where a vector conversion would go away because
supportable_convert_operation doesn't consider a noop conversion
(or a sign conversion). The following rectifies this, allowing
a NOP_EXPR and VIEW_CONVERT_EXPR for same mode types as supportable
conversion as we can RTL expand that just fine.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
I'll note that the .VEC_CONVERT IFNs from initial __builtin_convertvector
lowering survive unfolded until the veclower pass where, if the
conversions are not supported, they will be open-coded and not
folded either. I wonder why we chose to expand to .VEC_CONVERT
instead of using FLOAT_EXPR/FIX_TRUNC_EXPR/NOP_EXPR as appropriate
and lower those if not supported? At least I don't look forward to
add .VEC_CONVERT support to all conversion foldings?
I'll also note that the guards I put in place when adding
vector integer support to double-conversion folding will now
pessimize the case where neither (one of?) the former nor the
new conversion would be supported because of the type not
having vector mode.
PR middle-end/126788
* optabs-tree.cc (supportable_convert_operation): For same
modes allow NOP_EXPR and VIEW_CONVERT_EXPR.
* gcc.target/i386/pr126788.c: New testcase.
---
gcc/optabs-tree.cc | 4 ++++
gcc/testsuite/gcc.target/i386/pr126788.c | 24 ++++++++++++++++++++++++
2 files changed, 28 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/i386/pr126788.c
diff --git a/gcc/optabs-tree.cc b/gcc/optabs-tree.cc
index 5fbdcd3a730..5360a509f8d 100644
--- a/gcc/optabs-tree.cc
+++ b/gcc/optabs-tree.cc
@@ -375,6 +375,10 @@ supportable_convert_operation (enum tree_code code,
if (!VECTOR_MODE_P (m1) || !VECTOR_MODE_P (m2))
return false;
+ if (m1 == m2
+ && (CONVERT_EXPR_CODE_P (code) || code == VIEW_CONVERT_EXPR))
+ return true;
+
/* First check if we can done conversion directly. */
if ((code == FIX_TRUNC_EXPR
&& can_fix_p (m1,m2,TYPE_UNSIGNED (vectype_out), &truncp)
diff --git a/gcc/testsuite/gcc.target/i386/pr126788.c
b/gcc/testsuite/gcc.target/i386/pr126788.c
new file mode 100644
index 00000000000..0448284e8f6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr126788.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O -msse2" } */
+
+typedef int v2si __attribute__((vector_size (8)));
+typedef unsigned int v2usi __attribute__((vector_size (8)));
+typedef long long v2di __attribute__((vector_size (16)));
+
+v2si
+f1 (v2si a, v2si b)
+{
+
+ v2di z = __builtin_convertvector (a, v2di);
+ return __builtin_convertvector (z, v2si);
+}
+
+v2usi
+f2 (v2si a, v2si b)
+{
+
+ v2di z = __builtin_convertvector (a, v2di);
+ return __builtin_convertvector (z, v2usi);
+}
+
+/* { dg-final { scan-assembler-not "xmm" { target { ! ia32 } } } } */
--
2.51.0
