Re: [PATCH 5/14][AArch64] Add basic fp16 support

[Alan Lawrence <alan dot lawrence at arm dot com>]

Joseph Myers wrote:
>
> I'd think it would be desirable to share tests between ARM and AArch64 as 
> far as possible (where applicable to both - so not the tests for the 
> alternative format, and some of the gcc.target/arm/fp16-* tests using 
> scan-assembler might need adapting to work for AArch64).

I agree the most desirable outcome is for the ACLE spec to be normalized between 
the two architectures! In the meantime this implements the specification that we 
have...

I attach a new patch that adds common ARM / AArch64 tests in 
gcc.target/aarch64/fp16 (i.e. beside the shared 
gcc.target/aarch64/advsimd-intrinsics). I've adapted two of the previous tests 
such that they pass on both ARM and AArch64. I'd like to propose this as a patch 
5a, and to drop those tests from the original patch 5.

I'll follow-up with a sort-through of the ARM tests, moving only those that can 
be shared, in due course.

Cheers, Alan

diff --git a/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_1.c b/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_1.c
new file mode 100644
index 0000000000000000000000000000000000000000..a1c95fd28d14668c5cfa9cfb419c945878d7ac2b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_1.c
@@ -0,0 +1,34 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-mfp16-format=ieee" {target "arm*-*-*"} } */
+
+extern void abort (void);
+
+#define EPSILON 0.0001
+
+int
+main (int argc, char **argv)
+{
+  float f1 = 3.14159f;
+  float f2 = 2.718f;
+  /* This 'assembler' statement should be portable between ARM and AArch64.  */
+  asm volatile ("" : : : "memory");
+  __fp16 in1 = f1;
+  __fp16 in2 = f2;
+
+  /* Do the addition on __fp16's (implicitly converts both operands to
+     float32, adds, converts back to f16, then we convert back to f32).  */
+  __fp16 res1 = in1 + in2;
+  asm volatile ("" : : : "memory");
+  float f_res_1 = res1;
+
+  /* Do the addition on float32's (we convert both operands to f32, and add,
+     as above, but skip the final conversion f32 -> f16 -> f32).  */
+  float f1a = in1;
+  float f2a = in2;
+  float f_res_2 = f1a + f2a;
+
+  if (__builtin_fabs (f_res_2 - f_res_1) > EPSILON)
+    abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_2.c b/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_2.c
new file mode 100644
index 0000000000000000000000000000000000000000..6aa3e59c15e0eb85595871b47e8d8aa937cca47e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/fp16/f16_convs_2.c
@@ -0,0 +1,33 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-mfp16-format=ieee" {target "arm*-*-*"} } */
+
+extern void abort (void);
+
+#define EPSILON 0.0001
+
+int
+main (int argc, char **argv)
+{
+  int i1 = 3;
+  int i2 = 2;
+  /*  This 'assembler' should be portable across ARM and AArch64.  */
+  asm volatile ("" : : : "memory");
+
+  __fp16 in1 = i1;
+  __fp16 in2 = i2;
+
+  /* Do the addition on __fp16's (implicitly converts both operands to
+     float32, adds, converts back to f16, then we convert to int).  */
+  __fp16 res1 = in1 + in2;
+  asm volatile ("" : : : "memory");
+  int result1 = res1;
+
+  /* Do the addition on int's (we convert both operands directly to int, add,
+     and we're done).  */
+  int result2 = ((int) in1) + ((int) in2);
+
+  if (__builtin_abs (result2 - result1) > EPSILON)
+    abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/aarch64/fp16/fp16.exp b/gcc/testsuite/gcc.target/aarch64/fp16/fp16.exp
new file mode 100644
index 0000000000000000000000000000000000000000..7dc8d654a34004d280a1e9f6b9f39d868a60464a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/fp16/fp16.exp
@@ -0,0 +1,43 @@
+# Tests of 16-bit floating point (__fp16), for both ARM and AArch64.
+# Copyright (C) 2015 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# GCC testsuite that uses the `dg.exp' driver.
+
+# Exit immediately if this isn't an ARM or AArch64 target.
+if {![istarget arm*-*-*]
+    && ![istarget aarch64*-*-*]} then {
+  return
+}
+
+# Load support procs.
+load_lib gcc-dg.exp
+
+# If a testcase doesn't have special options, use these.
+global DEFAULT_CFLAGS
+if ![info exists DEFAULT_CFLAGS] then {
+    set DEFAULT_CFLAGS " -ansi -pedantic-errors"
+}
+
+# Initialize `dg'.
+dg-init
+
+# Main loop.
+dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cC\]]] \
+	"" $DEFAULT_CFLAGS
+
+# All done.
+dg-finish