From a05958934a426a8da179e0177feaee9c59935213 Mon Sep 17 00:00:00 2001
From: lkcl <lkcl@web>
Date: Fri, 21 Apr 2023 23:10:42 +0100
Subject: [PATCH]

---
 openpower/sv/rfc/ls013.mdwn | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/openpower/sv/rfc/ls013.mdwn b/openpower/sv/rfc/ls013.mdwn
index e6e77bd71..0e2a2f606 100644
--- a/openpower/sv/rfc/ls013.mdwn
+++ b/openpower/sv/rfc/ls013.mdwn
@@ -327,8 +327,41 @@ Add `MM` to the `Formats:` list for all of `FRT`, `FRA`, `FRB`, `XO (25:30)`,
 ## fmax instruction count
 
 32 instructions are required in SFFS to emulate fmax.
-<https://gcc.godbolt.org/z/6xba61To6>
 
+```
+#include <stdint.h>
+#include <string.h>
+
+inline uint64_t asuint64(double f) {
+    union {
+        double f;
+        uint64_t i;
+    } u = {f};
+    return u.i;
+}
+
+inline int issignaling(double v) {
+    // copied from glibc:
+    // https://github.com/bminor/glibc/blob/e2756903329365134089d23548e9083d23bc3dd9/sysdeps/ieee754/dbl-64/math_config.h#L101
+    uint64_t ix = asuint64(v);
+    return 2 * (ix ^ 0x0008000000000000) > 2 * 0x7ff8000000000000ULL;
+}
+
+double fmax(double x, double y) {
+    // copied from glibc:
+    // https://github.com/bminor/glibc/blob/e2756903329365134089d23548e9083d23bc3dd9/math/s_fmax_template.c
+    if(__builtin_isgreaterequal(x, y))
+        return x;
+    else if(__builtin_isless(x, y))
+        return y;
+    else if(issignaling(x) || issignaling(y))
+        return x + y;
+    else
+        return __builtin_isnan(y) ? x : y;
+}
+```
+
+Assembly listing:
 
 ```
     fmax(double, double):
-- 
2.30.2