Add narrowing multiply functions.

This patch adds the narrowing multiply functions from TS 18661-1 to
glibc's libm: fmul, fmull, dmull, f32mulf64, f32mulf32x, f32xmulf64
for all configurations; f32mulf64x, f32mulf128, f64mulf64x,
f64mulf128, f32xmulf64x, f32xmulf128, f64xmulf128 for configurations
with _Float64x and _Float128; __nldbl_dmull for ldbl-opt.

The changes are mostly essentially the same as for the narrowing add
functions, so the description of those generally applies to this patch
as well.  f32xmulf64 for i386 cannot use precision control as used for
add and subtract, because that would result in double rounding for
subnormal results, so that uses round-to-odd with long double
intermediate result instead.  The soft-fp support involves adding a
new FP_TRUNC_COOKED since soft-fp multiplication uses cooked inputs
and outputs.

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 mul.
	(libm-test-funcs-narrow): Likewise.
	* math/Versions (GLIBC_2.28): Add narrowing multiply functions.
	* math/bits/mathcalls-narrow.h (mul): Use __MATHCALL_NARROW.
	* math/gen-auto-libm-tests.c (test_functions): Add mul.
	* math/math-narrow.h (CHECK_NARROW_MUL): New macro.
	(NARROW_MUL_ROUND_TO_ODD): Likewise.
	(NARROW_MUL_TRIVIAL): Likewise.
	* soft-fp/op-common.h (FP_TRUNC_COOKED): Likewise.
	* sysdeps/ieee754/float128/float128_private.h (__fmull): New
	macro.
	(__dmull): Likewise.
	* sysdeps/ieee754/ldbl-opt/Makefile (libnldbl-calls): Add fmul and
	dmul.
	(CFLAGS-nldbl-dmul.c): New variable.
	(CFLAGS-nldbl-fmul.c): Likewise.
	* sysdeps/ieee754/ldbl-opt/Versions (GLIBC_2.28): Add
	__nldbl_dmull.
	* sysdeps/ieee754/ldbl-opt/nldbl-compat.h (__nldbl_dmull): New
	prototype.
	* manual/arith.texi (Misc FP Arithmetic): Document fmul, fmull,
	dmull, fMmulfN, fMmulfNx, fMxmulfN and fMxmulfNx.
	* math/auto-libm-test-in: Add tests of mul.
	* math/auto-libm-test-out-narrow-mul: New generated file.
	* math/libm-test-narrow-mul.inc: New file.
	* sysdeps/i386/fpu/s_f32xmulf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_f32xmulf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_fmul.c: Likewise.
	* sysdeps/ieee754/float128/s_f32mulf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64mulf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64xmulf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_dmull.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_f64xmulf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_fmull.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_dmull.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_fmull.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_dmull.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_fmull.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-dmul.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-fmul.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_dmull.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_fmul.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_fmull.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, 48 insertions, 0 deletions

diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index bb3c325fec..d102b99e23 100644
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -6445,6 +6445,54 @@ log2 min
 log2 min_subnorm
 log2 max
 
+mul 0 0
+mul 0 -0
+mul -0 0
+mul -0 -0
+mul max max
+mul max -max
+mul -max max
+mul -max -max
+mul min min
+mul min -min
+mul -min min
+mul -min -min
+mul min_subnorm min_subnorm
+mul min_subnorm -min_subnorm
+mul -min_subnorm min_subnorm
+mul -min_subnorm -min_subnorm
+mul 1 2
+mul 1 -2
+mul -1 2
+mul -1 -2
+mul 100.5 0.75
+mul 100.5 -0.75
+mul -100.5 0.75
+mul -100.5 -0.75
+# Cases where the product 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.  These examples have products of the form
+# (2^a + 1)(2^b + 1)/2^(a+b), where a is the width of the narrower
+# format, b is greater than the width of the wider format and factors
+# have been rearranged between the terms so that both terms do fit
+# within the wider format.
+# a = 24, b = 54
+mul 0x5000005p-24 0xccccccccccccdp-54
+# a = 24, b = 65
+mul 0x3000003p-24 0xaaaaaaaaaaaaaaabp-65
+# a = 24, b = 114
+mul 0x5000005p-24 0xcccccccccccccccccccccccccccdp-114
+# a = 53, b = 65
+mul 0x60000000000003p-53 0xaaaaaaaaaaaaaaabp-65
+# a = 53, b = 114
+mul 0xa0000000000005p-53 0xcccccccccccccccccccccccccccdp-114
+# a = 64, b = 114
+mul 0x50000000000000005p-64 0xcccccccccccccccccccccccccccdp-114
+# Similar, for double rounding to 64 bit of a product of 53-bit values.
+# This product equals 2^64 + 2^11 + 1.
+mul 97689974585 188829449
+
 pow 0 0
 pow 0 -0
 pow -0 0