Skip to content

[libc][math] Implement powf function correctly rounded to all rounding modes. #71188

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Nov 6, 2023
Merged

[libc][math] Implement powf function correctly rounded to all rounding modes. #71188

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
d8f84ec
[libc][math] Implement powf function correctly rounded to all roundin…
lntue Nov 3, 2023
e01e3f3
Fix hard-coded number of test cases in powf_test.
lntue Nov 3, 2023
baca7ee
Move exp2f and exp10f implementations to header libraries to be share…
lntue Nov 6, 2023
003d47e
Remove unnecessary header include in powf.cpp.
lntue Nov 6, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions libc/config/darwin/arm/entrypoints.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.nextafter
libc.src.math.nextafterf
libc.src.math.nextafterl
libc.src.math.powf
libc.src.math.remainderf
libc.src.math.remainder
libc.src.math.remainderl
Expand Down
1 change: 1 addition & 0 deletions libc/config/linux/aarch64/entrypoints.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.nextafter
libc.src.math.nextafterf
libc.src.math.nextafterl
libc.src.math.powf
libc.src.math.remainderf
libc.src.math.remainder
libc.src.math.remainderl
Expand Down
1 change: 1 addition & 0 deletions libc/config/linux/riscv/entrypoints.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.nextafter
libc.src.math.nextafterf
libc.src.math.nextafterl
libc.src.math.powf
libc.src.math.remainderf
libc.src.math.remainder
libc.src.math.remainderl
Expand Down
1 change: 1 addition & 0 deletions libc/config/linux/x86_64/entrypoints.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -329,6 +329,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.nextafter
libc.src.math.nextafterf
libc.src.math.nextafterl
libc.src.math.powf
libc.src.math.remainderf
libc.src.math.remainder
libc.src.math.remainderl
Expand Down
1 change: 1 addition & 0 deletions libc/config/windows/entrypoints.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.nextafter
libc.src.math.nextafterf
libc.src.math.nextafterl
libc.src.math.powf
libc.src.math.remainderf
libc.src.math.remainder
libc.src.math.remainderl
Expand Down
3 changes: 2 additions & 1 deletion libc/docs/math/index.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -420,7 +420,7 @@ Higher Math Functions
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| pow | | | | | | | | | | | | |
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| powf | | | | | | | | | | | | |
| powf | |check| | |check| | | |check| | |check| | | | |check| | | | | |
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| powl | | | | | | | | | | | | |
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
Expand Down Expand Up @@ -493,6 +493,7 @@ log |check| |check|
log10 |check| |check|
log1p |check| |check|
log2 |check| |check|
pow |check|
sin |check| large
sincos |check| large
sinh |check|
Expand Down
1 change: 1 addition & 0 deletions libc/spec/stdc.td
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -491,6 +491,7 @@ def StdC : StandardSpec<"stdc"> {
FunctionSpec<"nextafter", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
FunctionSpec<"nextafterl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>, ArgSpec<LongDoubleType>]>,

FunctionSpec<"powf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<FloatType>]>,
FunctionSpec<"pow", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,

FunctionSpec<"coshf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
Expand Down
70 changes: 60 additions & 10 deletions libc/src/math/generic/CMakeLists.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -625,12 +625,10 @@ add_entrypoint_object(
-O3
)

add_entrypoint_object(
exp2f
SRCS
exp2f.cpp
add_header_library(
exp2f_impl
HDRS
../exp2f.h
exp2f_impl.h
DEPENDS
.explogxf
libc.src.__support.FPUtil.except_value_utils
Expand All @@ -641,9 +639,20 @@ add_entrypoint_object(
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.common
libc.include.errno
libc.src.errno.errno
libc.include.math
)

add_entrypoint_object(
exp2f
SRCS
exp2f.cpp
HDRS
../exp2f.h
DEPENDS
.exp2f_impl
COMPILE_OPTIONS
-O3
)
Expand Down Expand Up @@ -675,12 +684,10 @@ add_entrypoint_object(
-O3
)

add_entrypoint_object(
exp10f
SRCS
exp10f.cpp
add_header_library(
exp10f_impl
HDRS
../exp10f.h
exp10f_impl.h
DEPENDS
.explogxf
libc.src.__support.FPUtil.fenv_impl
Expand All @@ -690,13 +697,26 @@ add_entrypoint_object(
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.common
libc.include.errno
libc.src.errno.errno
libc.include.math
COMPILE_OPTIONS
-O3
)

add_entrypoint_object(
exp10f
SRCS
exp10f.cpp
HDRS
../exp10f.h
DEPENDS
.exp10f_impl
COMPILE_OPTIONS
-O3
)

add_entrypoint_object(
expm1
SRCS
Expand Down Expand Up @@ -747,6 +767,36 @@ add_entrypoint_object(
-O3
)

add_entrypoint_object(
powf
SRCS
powf.cpp
HDRS
../powf.h
DEPENDS
.common_constants
.explogxf
.exp2f_impl
.exp10f_impl
libc.src.__support.builtin_wrappers
libc.src.__support.CPP.bit
libc.src.__support.CPP.optional
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.FPUtil.nearest_integer
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.FPUtil.sqrt
libc.src.__support.FPUtil.triple_double
libc.src.__support.macros.optimization
libc.include.errno
libc.src.errno.errno
libc.include.math
COMPILE_OPTIONS
-O3
)

add_entrypoint_object(
copysign
SRCS
Expand Down
87 changes: 87 additions & 0 deletions libc/src/math/generic/common_constants.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,51 @@ alignas(64) const double LOG_R[128] = {
0x1.5707a26bb8c66p-1, 0x1.5af405c3649ep-1, 0x1.5af405c3649ep-1,
0x1.5ee82aa24192p-1, 0x0.000000000000p0};

alignas(64) const double LOG2_R[128] = {
0x0.0000000000000p+0, 0x1.72c7ba20f7327p-7, 0x1.743ee861f3556p-6,
0x1.184b8e4c56af8p-5, 0x1.77394c9d958d5p-5, 0x1.d6ebd1f1febfep-5,
0x1.1bb32a600549dp-4, 0x1.4c560fe68af88p-4, 0x1.7d60496cfbb4cp-4,
0x1.960caf9abb7cap-4, 0x1.c7b528b70f1c5p-4, 0x1.f9c95dc1d1165p-4,
0x1.097e38ce60649p-3, 0x1.22dadc2ab3497p-3, 0x1.3c6fb650cde51p-3,
0x1.494f863b8df35p-3, 0x1.633a8bf437ce1p-3, 0x1.7046031c79f85p-3,
0x1.8a8980abfbd32p-3, 0x1.97c1cb13c7ec1p-3, 0x1.b2602497d5346p-3,
0x1.bfc67a7fff4ccp-3, 0x1.dac22d3e441d3p-3, 0x1.e857d3d361368p-3,
0x1.01d9bbcfa61d4p-2, 0x1.08bce0d95fa38p-2, 0x1.169c05363f158p-2,
0x1.1d982c9d52708p-2, 0x1.249cd2b13cd6cp-2, 0x1.32bfee370ee68p-2,
0x1.39de8e1559f6fp-2, 0x1.4106017c3eca3p-2, 0x1.4f6fbb2cec598p-2,
0x1.56b22e6b578e5p-2, 0x1.5dfdcf1eeae0ep-2, 0x1.6552b49986277p-2,
0x1.6cb0f6865c8eap-2, 0x1.7b89f02cf2aadp-2, 0x1.8304d90c11fd3p-2,
0x1.8a8980abfbd32p-2, 0x1.921800924dd3bp-2, 0x1.99b072a96c6b2p-2,
0x1.a8ff971810a5ep-2, 0x1.b0b67f4f4681p-2, 0x1.b877c57b1b07p-2,
0x1.c043859e2fdb3p-2, 0x1.c819dc2d45fe4p-2, 0x1.cffae611ad12bp-2,
0x1.d7e6c0abc3579p-2, 0x1.dfdd89d586e2bp-2, 0x1.e7df5fe538ab3p-2,
0x1.efec61b011f85p-2, 0x1.f804ae8d0cd02p-2, 0x1.0014332be0033p-1,
0x1.042bd4b9a7c99p-1, 0x1.08494c66b8efp-1, 0x1.0c6caaf0c5597p-1,
0x1.1096015dee4dap-1, 0x1.14c560fe68af9p-1, 0x1.18fadb6e2d3c2p-1,
0x1.1d368296b5255p-1, 0x1.217868b0c37e8p-1, 0x1.25c0a0463bebp-1,
0x1.2a0f3c340705cp-1, 0x1.2e644fac04fd8p-1, 0x1.2e644fac04fd8p-1,
0x1.32bfee370ee68p-1, 0x1.37222bb70747cp-1, 0x1.3b8b1c68fa6edp-1,
0x1.3ffad4e74f1d6p-1, 0x1.44716a2c08262p-1, 0x1.44716a2c08262p-1,
0x1.48eef19317991p-1, 0x1.4d7380dcc422dp-1, 0x1.51ff2e30214bcp-1,
0x1.5692101d9b4a6p-1, 0x1.5b2c3da19723bp-1, 0x1.5b2c3da19723bp-1,
0x1.5fcdce2727ddbp-1, 0x1.6476d98ad990ap-1, 0x1.6927781d932a8p-1,
0x1.6927781d932a8p-1, 0x1.6ddfc2a78fc63p-1, 0x1.729fd26b707c8p-1,
0x1.7767c12967a45p-1, 0x1.7767c12967a45p-1, 0x1.7c37a9227e7fbp-1,
0x1.810fa51bf65fdp-1, 0x1.810fa51bf65fdp-1, 0x1.85efd062c656dp-1,
0x1.8ad846cf369a4p-1, 0x1.8ad846cf369a4p-1, 0x1.8fc924c89ac84p-1,
0x1.94c287492c4dbp-1, 0x1.94c287492c4dbp-1, 0x1.99c48be2063c8p-1,
0x1.9ecf50bf43f13p-1, 0x1.9ecf50bf43f13p-1, 0x1.a3e2f4ac43f6p-1,
0x1.a8ff971810a5ep-1, 0x1.a8ff971810a5ep-1, 0x1.ae255819f022dp-1,
0x1.b35458761d479p-1, 0x1.b35458761d479p-1, 0x1.b88cb9a2ab521p-1,
0x1.b88cb9a2ab521p-1, 0x1.bdce9dcc96187p-1, 0x1.c31a27dd00b4ap-1,
0x1.c31a27dd00b4ap-1, 0x1.c86f7b7ea4a89p-1, 0x1.c86f7b7ea4a89p-1,
0x1.cdcebd2373995p-1, 0x1.d338120a6dd9dp-1, 0x1.d338120a6dd9dp-1,
0x1.d8aba045b01c8p-1, 0x1.d8aba045b01c8p-1, 0x1.de298ec0bac0dp-1,
0x1.de298ec0bac0dp-1, 0x1.e3b20546f554ap-1, 0x1.e3b20546f554ap-1,
0x1.e9452c8a71028p-1, 0x1.e9452c8a71028p-1, 0x1.eee32e2aeccbfp-1,
0x1.eee32e2aeccbfp-1, 0x1.f48c34bd1e96fp-1, 0x1.f48c34bd1e96fp-1,
0x1.fa406bd2443dfp-1, 0x1.0000000000000p0};

// Generated by Sollya with:
// for i from 0 to 127 do {
// r = 2^-8 * ceil( 2^8 * (1 - 2^(-8)) / (1 + i*2^-7) );
Expand Down Expand Up @@ -395,6 +440,48 @@ alignas(64) const int S2[193] = {
-0x1cd, -0x1d1, -0x1d5, -0x1d9, -0x1dd, -0x1e0, -0x1e4, -0x1e8, -0x1ec,
-0x1f0, -0x1f4, -0x1f8, -0x1fc};

alignas(64) const double R2[193] = {
0x1.0101p0, 0x1.00fdp0, 0x1.00f9p0, 0x1.00f5p0, 0x1.00f1p0,
0x1.00edp0, 0x1.00e9p0, 0x1.00e5p0, 0x1.00e1p0, 0x1.00ddp0,
0x1.00d9p0, 0x1.00d5p0, 0x1.00d1p0, 0x1.00cdp0, 0x1.00c9p0,
0x1.00c5p0, 0x1.00c1p0, 0x1.00bdp0, 0x1.00b9p0, 0x1.00b4p0,
0x1.00bp0, 0x1.00acp0, 0x1.00a8p0, 0x1.00a4p0, 0x1.00ap0,
0x1.009cp0, 0x1.0098p0, 0x1.0094p0, 0x1.009p0, 0x1.008cp0,
0x1.0088p0, 0x1.0084p0, 0x1.008p0, 0x1.007cp0, 0x1.0078p0,
0x1.0074p0, 0x1.007p0, 0x1.006cp0, 0x1.0068p0, 0x1.0064p0,
0x1.006p0, 0x1.005cp0, 0x1.0058p0, 0x1.0054p0, 0x1.005p0,
0x1.004cp0, 0x1.0048p0, 0x1.0044p0, 0x1.004p0, 0x1.003cp0,
0x1.0038p0, 0x1.0034p0, 0x1.003p0, 0x1.002cp0, 0x1.0028p0,
0x1.0024p0, 0x1.002p0, 0x1.001cp0, 0x1.0018p0, 0x1.0014p0,
0x1.001p0, 0x1.000cp0, 0x1.0008p0, 0x1.0004p0, 0x1p0,
0x1.fff8p-1, 0x1.fffp-1, 0x1.ffe8p-1, 0x1.ffep-1, 0x1.ffd8p-1,
0x1.ffdp-1, 0x1.ffc8p-1, 0x1.ffcp-1, 0x1.ffb8p-1, 0x1.ffbp-1,
0x1.ffa8p-1, 0x1.ffap-1, 0x1.ff98p-1, 0x1.ff9p-1, 0x1.ff88p-1,
0x1.ff8p-1, 0x1.ff78p-1, 0x1.ff7p-1, 0x1.ff68p-1, 0x1.ff6p-1,
0x1.ff58p-1, 0x1.ff5p-1, 0x1.ff48p-1, 0x1.ff4p-1, 0x1.ff38p-1,
0x1.ff3p-1, 0x1.ff28p-1, 0x1.ff2p-1, 0x1.ff18p-1, 0x1.ff1p-1,
0x1.ff08p-1, 0x1.ffp-1, 0x1.fef8p-1, 0x1.fefp-1, 0x1.fee8p-1,
0x1.feep-1, 0x1.fed8p-1, 0x1.fedp-1, 0x1.fec8p-1, 0x1.fecp-1,
0x1.feb8p-1, 0x1.febp-1, 0x1.fea8p-1, 0x1.feap-1, 0x1.fe98p-1,
0x1.fe92p-1, 0x1.fe8ap-1, 0x1.fe82p-1, 0x1.fe7ap-1, 0x1.fe72p-1,
0x1.fe6ap-1, 0x1.fe62p-1, 0x1.fe5ap-1, 0x1.fe52p-1, 0x1.fe4ap-1,
0x1.fe42p-1, 0x1.fe3ap-1, 0x1.fe32p-1, 0x1.fe2ap-1, 0x1.fe22p-1,
0x1.fe1ap-1, 0x1.fe12p-1, 0x1.fe0ap-1, 0x1.fe02p-1, 0x1.fdfap-1,
0x1.fdf2p-1, 0x1.fdeap-1, 0x1.fde2p-1, 0x1.fddap-1, 0x1.fdd2p-1,
0x1.fdcap-1, 0x1.fdc2p-1, 0x1.fdbap-1, 0x1.fdb2p-1, 0x1.fdaap-1,
0x1.fda2p-1, 0x1.fd9ap-1, 0x1.fd92p-1, 0x1.fd8cp-1, 0x1.fd84p-1,
0x1.fd7cp-1, 0x1.fd74p-1, 0x1.fd6cp-1, 0x1.fd64p-1, 0x1.fd5cp-1,
0x1.fd54p-1, 0x1.fd4cp-1, 0x1.fd44p-1, 0x1.fd3cp-1, 0x1.fd34p-1,
0x1.fd2cp-1, 0x1.fd24p-1, 0x1.fd1cp-1, 0x1.fd14p-1, 0x1.fd0cp-1,
0x1.fd04p-1, 0x1.fcfcp-1, 0x1.fcf4p-1, 0x1.fcecp-1, 0x1.fce4p-1,
0x1.fcdcp-1, 0x1.fcd6p-1, 0x1.fccep-1, 0x1.fcc6p-1, 0x1.fcbep-1,
0x1.fcb6p-1, 0x1.fcaep-1, 0x1.fca6p-1, 0x1.fc9ep-1, 0x1.fc96p-1,
0x1.fc8ep-1, 0x1.fc86p-1, 0x1.fc7ep-1, 0x1.fc76p-1, 0x1.fc6ep-1,
0x1.fc66p-1, 0x1.fc5ep-1, 0x1.fc56p-1, 0x1.fc4ep-1, 0x1.fc46p-1,
0x1.fc4p-1, 0x1.fc38p-1, 0x1.fc3p-1, 0x1.fc28p-1, 0x1.fc2p-1,
0x1.fc18p-1, 0x1.fc1p-1, 0x1.fc08p-1,
};

// Logarithm range reduction - Step 3:
// r(k) = 2^-21 round(2^21 / (1 + k*2^-21)) for k = -80 .. 80.
// Output range:
Expand Down
5 changes: 5 additions & 0 deletions libc/src/math/generic/common_constants.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,9 @@ extern const double CD[128];
extern const double LOG_R[128];
extern const NumberPair<double> LOG_R_DD[128];

// Lookup table for -log2(r)
extern const double LOG2_R[128];

// Minimax polynomial for (log(1 + x) - x)/x^2, generated by sollya with:
// > P = fpminimax((log(1 + x) - x)/x^2, 5, [|D...|], [-2^-8, 2^-7]);
constexpr double LOG_COEFFS[6] = {-0x1.fffffffffffffp-2, 0x1.5555555554a9bp-2,
Expand All @@ -45,6 +48,8 @@ extern const int S2[193];
extern const int S3[161];
extern const int S4[130];

extern const double R2[193];

// log(2) generated by Sollya with:
// > a = 2^-43 * nearestint(2^43*log(2));
// LSB = 2^-43 is chosen so that e_x * LOG_2_HI is exact for -1075 < e_x < 1024.
Expand Down
Loading