add riscv64 architecture support

Author: Alex Suykov <alex.suykov@gmail.com>
Author: Aric Belsito <lluixhi@gmail.com>
Author: Drew DeVault <sir@cmpwn.com>
Author: Michael Clark <mjc@sifive.com>
Author: Michael Forney <mforney@mforney.org>
Author: Stefan O'Rear <sorear2@gmail.com>

This port has involved the work of many people over several years. I
have tried to ensure that everyone with substantial contributions has
been credited above; if any omissions are found they will be noted
later in an update to the authors/contributors list in the COPYRIGHT
file.

The version committed here comes from the riscv/riscv-musl repo's
commit 3fe7e2c75df78eef42dcdc352a55757729f451e2, with minor changes by
me for issues found during final review:

- a_ll/a_sc atomics are removed (according to the ISA spec, lr/sc
  are not safe to use in separate inline asm fragments)

- a_cas[_p] is fixed to be a memory barrier

- the call from the _start assembly into the C part of crt1/ldso is
  changed to allow for the possibility that the linker does not place
  them nearby each other.

- DTP_OFFSET is defined correctly so that local-dynamic TLS works

- reloc.h LDSO_ARCH logic is simplified and made explicit.

- unused, non-functional crti/n asm files are removed.

- an empty .sdata section is added to crt1 so that the
  __global_pointer reference is resolvable.

- indentation style errors in some asm files are fixed.

12 files changed, 180 insertions, 0 deletions

diff --git a/src/math/riscv64/copysign.c b/src/math/riscv64/copysign.c
new file mode 100644
index 00000000..c7854178
--- /dev/null
+++ b/src/math/riscv64/copysign.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double copysign(double x, double y)
+{
+	__asm__ ("fsgnj.d %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../copysign.c"
+
+#endif
diff --git a/src/math/riscv64/copysignf.c b/src/math/riscv64/copysignf.c
new file mode 100644
index 00000000..a125611a
--- /dev/null
+++ b/src/math/riscv64/copysignf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float copysignf(float x, float y)
+{
+	__asm__ ("fsgnj.s %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../copysignf.c"
+
+#endif
diff --git a/src/math/riscv64/fabs.c b/src/math/riscv64/fabs.c
new file mode 100644
index 00000000..5290b6f0
--- /dev/null
+++ b/src/math/riscv64/fabs.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double fabs(double x)
+{
+	__asm__ ("fabs.d %0, %1" : "=f"(x) : "f"(x));
+	return x;
+}
+
+#else
+
+#include "../fabs.c"
+
+#endif
diff --git a/src/math/riscv64/fabsf.c b/src/math/riscv64/fabsf.c
new file mode 100644
index 00000000..f5032e35
--- /dev/null
+++ b/src/math/riscv64/fabsf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float fabsf(float x)
+{
+	__asm__ ("fabs.s %0, %1" : "=f"(x) : "f"(x));
+	return x;
+}
+
+#else
+
+#include "../fabsf.c"
+
+#endif
diff --git a/src/math/riscv64/fma.c b/src/math/riscv64/fma.c
new file mode 100644
index 00000000..99b05713
--- /dev/null
+++ b/src/math/riscv64/fma.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double fma(double x, double y, double z)
+{
+	__asm__ ("fmadd.d %0, %1, %2, %3" : "=f"(x) : "f"(x), "f"(y), "f"(z));
+	return x;
+}
+
+#else
+
+#include "../fma.c"
+
+#endif
diff --git a/src/math/riscv64/fmaf.c b/src/math/riscv64/fmaf.c
new file mode 100644
index 00000000..f9dc47ed
--- /dev/null
+++ b/src/math/riscv64/fmaf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float fmaf(float x, float y, float z)
+{
+	__asm__ ("fmadd.s %0, %1, %2, %3" : "=f"(x) : "f"(x), "f"(y), "f"(z));
+	return x;
+}
+
+#else
+
+#include "../fmaf.c"
+
+#endif
diff --git a/src/math/riscv64/fmax.c b/src/math/riscv64/fmax.c
new file mode 100644
index 00000000..023709cd
--- /dev/null
+++ b/src/math/riscv64/fmax.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double fmax(double x, double y)
+{
+	__asm__ ("fmax.d %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../fmax.c"
+
+#endif
diff --git a/src/math/riscv64/fmaxf.c b/src/math/riscv64/fmaxf.c
new file mode 100644
index 00000000..863d2bd1
--- /dev/null
+++ b/src/math/riscv64/fmaxf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float fmaxf(float x, float y)
+{
+	__asm__ ("fmax.s %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../fmaxf.c"
+
+#endif
diff --git a/src/math/riscv64/fmin.c b/src/math/riscv64/fmin.c
new file mode 100644
index 00000000..a4e3b067
--- /dev/null
+++ b/src/math/riscv64/fmin.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double fmin(double x, double y)
+{
+	__asm__ ("fmin.d %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../fmin.c"
+
+#endif
diff --git a/src/math/riscv64/fminf.c b/src/math/riscv64/fminf.c
new file mode 100644
index 00000000..32156e80
--- /dev/null
+++ b/src/math/riscv64/fminf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float fminf(float x, float y)
+{
+	__asm__ ("fmin.s %0, %1, %2" : "=f"(x) : "f"(x), "f"(y));
+	return x;
+}
+
+#else
+
+#include "../fminf.c"
+
+#endif
diff --git a/src/math/riscv64/sqrt.c b/src/math/riscv64/sqrt.c
new file mode 100644
index 00000000..867a504c
--- /dev/null
+++ b/src/math/riscv64/sqrt.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double sqrt(double x)
+{
+	__asm__ ("fsqrt.d %0, %1" : "=f"(x) : "f"(x));
+	return x;
+}
+
+#else
+
+#include "../sqrt.c"
+
+#endif
diff --git a/src/math/riscv64/sqrtf.c b/src/math/riscv64/sqrtf.c
new file mode 100644
index 00000000..610c2cf8
--- /dev/null
+++ b/src/math/riscv64/sqrtf.c
@@ -0,0 +1,15 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float sqrtf(float x)
+{
+	__asm__ ("fsqrt.s %0, %1" : "=f"(x) : "f"(x));
+	return x;
+}
+
+#else
+
+#include "../sqrtf.c"
+
+#endif