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51 lines
2.0 KiB
Diff
51 lines
2.0 KiB
Diff
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From 91f99d323b39dc0c06c40038791db9861d4b76b9 Mon Sep 17 00:00:00 2001
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From: Kito Cheng <kito.cheng@sifive.com>
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Date: Mon, 12 Jul 2021 17:17:21 +0800
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Subject: [PATCH] Minimal support for ISO/IEC TS 18661-3.
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- GCC will set __FLT_EVAL_METHOD__ to 16 if __fp16 supported, e.g.
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cortex-a55/aarch64.
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- $ aarch64-unknown-elf-gcc -v 2>&1 |grep version
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gcc version 9.2.0 (GCC)
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- $ aarch64-unknown-elf-gcc -E -dM -mcpu=cortex-a55 - < /dev/null |grep FLT_EVAL_METHOD
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#define __FLT_EVAL_METHOD__ 16
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#define __FLT_EVAL_METHOD_TS_18661_3__ 16
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#define __FLT_EVAL_METHOD_C99__ 16
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- The behavior of __FLT_EVAL_METHOD__ == 16 is same as
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__FLT_EVAL_METHOD__ == 0 except for float16_t, but newlib didn't
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support float16_t.
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ISO/IEC TS 18661-3:
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http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2405.pdf
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V2 Changes:
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- List Howland, Craig D as co-author since he provide the draft of comment
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in math.h.
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Co-authored-by: "Howland, Craig D" <howland@LGSInnovations.com>
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---
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newlib/libc/include/math.h | 12 +++++++++++-
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1 file changed, 11 insertions(+), 1 deletion(-)
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--- a/newlib/libc/include/math.h
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+++ b/newlib/libc/include/math.h
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@@ -146,7 +146,17 @@
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#define __TMP_FLT_EVAL_METHOD
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#endif /* FLT_EVAL_METHOD */
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#if defined FLT_EVAL_METHOD
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- #if FLT_EVAL_METHOD == 0
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+/* FLT_EVAL_METHOD == 16 has meaning as defined in ISO/IEC TS 18661-3,
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+ * which provides non-compliant extensions to C and POSIX (by adding
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+ * additional positive values for FLT_EVAL_METHOD). It effectively has
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+ * same meaning as the C99 and C11 definitions for value 0, while also
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+ * serving as a flag that the _Float16 (float16_t) type exists.
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+ *
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+ * FLT_EVAL_METHOD could be any number of bits of supported floating point
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+ * format (e.g. 32, 64, 128), but currently only AArch64 and few other targets
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+ * might define that as 16. */
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+ #if (FLT_EVAL_METHOD == 0) \
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+ || (FLT_EVAL_METHOD == 16)
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typedef float float_t;
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typedef double double_t;
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#elif FLT_EVAL_METHOD == 1
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