Add narrowing divide functions.

This patch adds the narrowing divide functions from TS 18661-1 to
glibc's libm: fdiv, fdivl, ddivl, f32divf64, f32divf32x, f32xdivf64
for all configurations; f32divf64x, f32divf128, f64divf64x,
f64divf128, f32xdivf64x, f32xdivf128, f64xdivf128 for configurations
with _Float64x and _Float128; __nldbl_ddivl for ldbl-opt.

The changes are mostly essentially the same as for the other narrowing
functions, so the description of those generally applies to this patch
as well.

Tested for x86_64, x86, mips64 (all three ABIs, both hard and soft
float) and powerpc, and with build-many-glibcs.py.

	* math/Makefile (libm-narrow-fns): Add div.
	(libm-test-funcs-narrow): Likewise.
	* math/Versions (GLIBC_2.28): Add narrowing divide functions.
	* math/bits/mathcalls-narrow.h (div): Use __MATHCALL_NARROW.
	* math/gen-auto-libm-tests.c (test_functions): Add div.
	* math/math-narrow.h (CHECK_NARROW_DIV): New macro.
	(NARROW_DIV_ROUND_TO_ODD): Likewise.
	(NARROW_DIV_TRIVIAL): Likewise.
	* sysdeps/ieee754/float128/float128_private.h (__fdivl): New
	macro.
	(__ddivl): Likewise.
	* sysdeps/ieee754/ldbl-opt/Makefile (libnldbl-calls): Add fdiv and
	ddiv.
	(CFLAGS-nldbl-ddiv.c): New variable.
	(CFLAGS-nldbl-fdiv.c): Likewise.
	* sysdeps/ieee754/ldbl-opt/Versions (GLIBC_2.28): Add
	__nldbl_ddivl.
	* sysdeps/ieee754/ldbl-opt/nldbl-compat.h (__nldbl_ddivl): New
	prototype.
	* manual/arith.texi (Misc FP Arithmetic): Document fdiv, fdivl,
	ddivl, fMdivfN, fMdivfNx, fMxdivfN and fMxdivfNx.
	* math/auto-libm-test-in: Add tests of div.
	* math/auto-libm-test-out-narrow-div: New generated file.
	* math/libm-test-narrow-div.inc: New file.
	* sysdeps/i386/fpu/s_f32xdivf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_f32xdivf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_fdiv.c: Likewise.
	* sysdeps/ieee754/float128/s_f32divf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64divf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64xdivf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_ddivl.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_f64xdivf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_fdivl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_ddivl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_fdivl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_ddivl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_fdivl.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-ddiv.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-fdiv.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_ddivl.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_fdiv.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_fdivl.c: Likewise.
	* sysdeps/powerpc/fpu/libm-test-ulps: Update.
	* sysdeps/mach/hurd/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/alpha/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/arm/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/hppa/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/nios2/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/riscv/rv64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sh/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.

1 files changed, 74 insertions, 0 deletions

diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index d102b99..7853285 100644
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -4758,6 +4758,80 @@ ctanh -min 0
 ctanh min_subnorm 0
 ctanh -min_subnorm 0
 
+div 0 min
+div 0 -min
+div 0 min_subnorm
+div 0 -min_subnorm
+div 0 max
+div 0 -max
+div -0 min
+div -0 -min
+div -0 min_subnorm
+div -0 -min_subnorm
+div -0 max
+div -0 -max
+div max max xfail:ibm128-libgcc
+div max -max xfail:ibm128-libgcc
+div -max max xfail:ibm128-libgcc
+div -max -max xfail:ibm128-libgcc
+div min min
+div min -min
+div -min min
+div -min -min
+div min_subnorm min_subnorm
+div min_subnorm -min_subnorm
+div -min_subnorm min_subnorm
+div -min_subnorm -min_subnorm
+div max min xfail-rounding:ibm128-libgcc
+div max -min xfail-rounding:ibm128-libgcc
+div -max min xfail-rounding:ibm128-libgcc
+div -max -min xfail-rounding:ibm128-libgcc
+div max min_subnorm xfail-rounding:ibm128-libgcc
+div max -min_subnorm xfail-rounding:ibm128-libgcc
+div -max min_subnorm xfail-rounding:ibm128-libgcc
+div -max -min_subnorm xfail-rounding:ibm128-libgcc
+div min max xfail-rounding:ibm128-libgcc
+div min -max xfail-rounding:ibm128-libgcc
+div -min max xfail-rounding:ibm128-libgcc
+div -min -max xfail-rounding:ibm128-libgcc
+div min_subnorm max xfail-rounding:ibm128-libgcc
+div min_subnorm -max xfail-rounding:ibm128-libgcc
+div -min_subnorm max xfail-rounding:ibm128-libgcc
+div -min_subnorm -max xfail-rounding:ibm128-libgcc
+div 1 2
+div 1 -2
+div -1 2
+div -1 -2
+div 100.5 0.75
+div 100.5 -0.75
+div -100.5 0.75
+div -100.5 -0.75
+
+# Cases where the ratio of two values in a wider format is very close
+# to half way between two representable values in a narrower format,
+# so that double rounding would sometimes yield the wrong result.  For
+# a narrower format of width a and a wider format of width w, take
+# b = w - a; these examples are of the form
+# (1 + 2^-a + 2^-b + 2^(1-w)) / (1 + 2^-b).  These examples have
+# ratios of the form (1 + 2^-a) to the width of the wider format, but
+# the mathematical value is slightly greater, so that rounding once
+# should round the result up but double rounding would wrongly round
+# the result down.
+# a = 24, w = 53.
+div 0x1.0000010800001p0 0x1.00000008p0
+# a = 24, w = 64.
+div 0x1.0000010001000002p0 0x1.0000000001p0
+# a = 24, w = 113.
+div 0x1.0000010000000000000000800001p0 0x1.00000000000000000000008p0
+# a = 53, w = 64.
+div 0x1.0020000000000802p0 0x1.002p0
+# a = 53, w = 113.
+div 0x1.0000000000000810000000000001p0 0x1.000000000000001p0
+# a = 64, w = 113.
+div 0x1.0000000000008001000000000001p0 0x1.0000000000008p0
+# Similar, for double rounding to 64-bit of a division of 53-bit values.
+div 0x1ffe1p0 0xfffp0
+
 erf 0
 erf -0
 erf 0.125