From acfe6d033eafe12d61ad91f496850b1bf58c6f98 Mon Sep 17 00:00:00 2001
From: Alexander Monakov <amonakov@ispras.ru>
Date: Tue, 7 Jan 2020 15:53:03 +0300
Subject: [PATCH] math: move i386 sqrt to C with inline asm

---
 src/math/i386/sqrt.c | 15 +++++++++++++++
 src/math/i386/sqrt.s | 21 ---------------------
 2 files changed, 15 insertions(+), 21 deletions(-)
 create mode 100644 src/math/i386/sqrt.c
 delete mode 100644 src/math/i386/sqrt.s

diff --git a/src/math/i386/sqrt.c b/src/math/i386/sqrt.c
new file mode 100644
index 00000000..934fbcca
--- /dev/null
+++ b/src/math/i386/sqrt.c
@@ -0,0 +1,15 @@
+#include "libm.h"
+
+double sqrt(double x)
+{
+	union ldshape ux;
+	unsigned fpsr;
+	__asm__ ("fsqrt; fnstsw %%ax": "=t"(ux.f), "=a"(fpsr) : "0"(x));
+	if ((ux.i.m & 0x7ff) != 0x400)
+		return (double)ux.f;
+	/* Rounding to double would have encountered an exact halfway case.
+	   Adjust mantissa downwards if fsqrt rounded up, else upwards.
+	   (result of fsqrt could not have been exact) */
+	ux.i.m ^= (fpsr & 0x200) + 0x300;
+	return (double)ux.f;
+}
diff --git a/src/math/i386/sqrt.s b/src/math/i386/sqrt.s
deleted file mode 100644
index 57837e25..00000000
--- a/src/math/i386/sqrt.s
+++ /dev/null
@@ -1,21 +0,0 @@
-.global sqrt
-.type sqrt,@function
-sqrt:	fldl 4(%esp)
-	fsqrt
-	fnstsw %ax
-	sub $12,%esp
-	fld %st(0)
-	fstpt (%esp)
-	mov (%esp),%ecx
-	and $0x7ff,%ecx
-	cmp $0x400,%ecx
-	jnz 1f
-	and $0x200,%eax
-	sub $0x100,%eax
-	sub %eax,(%esp)
-	fstp %st(0)
-	fldt (%esp)
-1:	add $12,%esp
-	fstpl 4(%esp)
-	fldl 4(%esp)
-	ret
-- 
2.25.1