summaryrefslogtreecommitdiff
path: root/libc/src/math/generic/log10.cpp
AgeCommit message (Collapse)Author
2025-10-05[libc][math] Refactor exp2 implementation to header-only in ↵Muhammad Bassiouni
src/__support/math folder. (#161297) Part of #147386 in preparation for: https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450
2025-03-11[libc] Provide more fine-grained control of FMA instruction for ARM targets. ↵lntue
(#130700)
2025-03-05[libc][math] Add skip accurate pass option for exp*, log*, and powf ↵lntue
functions. (#129831)
2024-10-26[libc][math] Add tests and fix some issues with FTZ/DAZ modes. (#113744)lntue
2024-07-12[libc] Migrate to using LIBC_NAMESPACE_DECL for namespace declaration (#98597)Petr Hosek
This is a part of #97655.
2024-07-12Revert "[libc] Migrate to using LIBC_NAMESPACE_DECL for namespace ↵Mehdi Amini
declaration" (#98593) Reverts llvm/llvm-project#98075 bots are broken
2024-07-11[libc] Migrate to using LIBC_NAMESPACE_DECL for namespace declaration (#98075)Petr Hosek
This is a part of #97655.
2024-03-20[libc][NFC] Move `Sign` type to separate header (#85930)Guillaume Chatelet
2024-02-16[reland][libc][NFC] Use user defined literals to build 128 and 256 bit ↵Guillaume Chatelet
constants (#81998) - #81835 - Fix for platforms where uint64_t is not available
2024-02-15Revert "[reland][libc][NFC] Use user defined literals to build 128 and 256 ↵Guillaume Chatelet
bit constants" (#81882) Reverts llvm/llvm-project#81835 This is breaking arm32 which does not support 64 bit types.
2024-02-15[reland][libc][NFC] Use user defined literals to build 128 and 256 bit ↵Guillaume Chatelet
constants (#81835) This is a reland of #81746
2024-02-14Revert "[libc][NFC] Use user defined literals to build 128 and 256 bit ↵Guillaume Chatelet
constants." (#81771) Reverts llvm/llvm-project#81746
2024-02-14[libc][NFC] Use user defined literals to build 128 and 256 bit constants. ↵Guillaume Chatelet
(#81746)
2024-01-30[libc][NFC] Rename `FPBits` nan functions (#79998)Guillaume Chatelet
- [libc][NFC] Rename FPBits nan functions - rename build_signaling_nan in signaling_nan - rename build_quiet_nan to quiet_nan
2024-01-23[reland][libc] Remove unnecessary `FPBits` functions and properties (#79128)Guillaume Chatelet
- reland #79113 - Fix aarch64 RISC-V build
2024-01-23Revert "[libc] Remove unnecessary `FPBits` functions and properties" (#79118)Guillaume Chatelet
Reverts llvm/llvm-project#79113 It broke aarch64 build bot machines.
2024-01-23[libc] Remove unnecessary `FPBits` functions and properties (#79113)Guillaume Chatelet
This patch reduces the surface of `FPBits`.
2024-01-18[libc][NFC] Use the Sign type for DyadicFloat (#78577)Guillaume Chatelet
2024-01-18[libc][NFC] Introduce a Sign type for FPBits (#78500)Guillaume Chatelet
Another patch is needed to cover `DyadicFloat` and `NormalFloat` constructors.
2024-01-04[libc][NFC] Simplify `FPBits` (#76835)Guillaume Chatelet
This patch reduces the scope of `FPBits` exported variables and functions. It also moves storage up into `FPRep` and tries to make the default and specialized versions of `FPBits` more uniform. The next step is to move the specialization from `FPBits` to `FPRep` so we can manipulate floating point representations through `FPType` alone - that is - independently from the host architecture.
2023-12-15[libc][NFC] Rename `MANTISSA_WIDTH` in `FRACTION_LEN` (#75489)Guillaume Chatelet
This one might be a bit controversial since the terminology has been introduced from the start but I think `FRACTION_LEN` is a better name here. AFAICT it really is "the number of bits after the decimal dot when the number is in normal form." `MANTISSA_WIDTH` is less precise as it's unclear whether we take the leading bit into account. This patch also renames most of the properties to use the `_LEN` suffix and fixes useless casts or variables.
2023-12-13Revert "[libc][NFC] Implement `FPBits` in terms of `FloatProperties` to ↵Guillaume Chatelet
reduce clutter" (#75304) Reverts llvm/llvm-project#75196 GCC complains about change of meaning for `FPBits` ``` /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian-fullbuild/libc-x86_64-debian-gcc-fullbuild-dbg/llvm-project/libc/src/__support/FPUtil/generic/FMod.h:188:9: error: declaration of ‘using FPBits = struct __llvm_libc_18_0_0_git::fputil::FPBits<T>’ changes meaning of ‘FPBits’ [-fpermissive] 188 | using FPBits = FPBits<T>; | ^~~~~~ ``` I'll reland with a different name.
2023-12-13[libc][NFC] Implement `FPBits` in terms of `FloatProperties` to reduce ↵Guillaume Chatelet
clutter (#75196) Also make type naming consistent: - `UIntType` instead of `intU_t` - `FPBits` instead of `FPBits_t`, `FPB`
2023-12-08[libc][NFC] Clean up conversion warnings in math function implementations. ↵lntue
(#74697)
2023-09-26[libc] Mass replace enclosing namespace (#67032)Guillaume Chatelet
This is step 4 of https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079
2023-05-23[libc][math] Implement double precision log function correctly rounded to ↵Tue Ly
all rounding modes. Implement double precision log function correctly rounded to all rounding modes. See https://reviews.llvm.org/D150014 for a more detail description of the algorithm. **Performance** - For `0.5 <= x <= 2`, the fast pass hitting rate is about 99.93%. - Reciprocal throughput from CORE-MATH's perf tool on Ryzen 5900X: ``` $ ./perf.sh log GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH reciprocal throughput -- with FMA [####################] 100 % Ntrial = 20 ; Min = 17.465 + 0.596 clc/call; Median-Min = 0.602 clc/call; Max = 18.389 clc/call; -- CORE-MATH reciprocal throughput -- without FMA (-march=x86-64-v2) [####################] 100 % Ntrial = 20 ; Min = 54.961 + 2.606 clc/call; Median-Min = 2.180 clc/call; Max = 59.583 clc/call; -- System LIBC reciprocal throughput -- [####################] 100 % Ntrial = 20 ; Min = 12.608 + 0.276 clc/call; Median-Min = 0.359 clc/call; Max = 13.147 clc/call; -- LIBC reciprocal throughput -- with FMA [####################] 100 % Ntrial = 20 ; Min = 20.952 + 0.468 clc/call; Median-Min = 0.602 clc/call; Max = 21.881 clc/call; -- LIBC reciprocal throughput -- without FMA [####################] 100 % Ntrial = 20 ; Min = 18.569 + 0.552 clc/call; Median-Min = 0.601 clc/call; Max = 19.259 clc/call; ``` - Latency from CORE-MATH's perf tool on Ryzen 5900X: ``` $ ./perf.sh log --latency GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH latency -- with FMA [####################] 100 % Ntrial = 20 ; Min = 48.431 + 0.699 clc/call; Median-Min = 0.073 clc/call; Max = 51.269 clc/call; -- CORE-MATH latency -- without FMA (-march=x86-64-v2) [####################] 100 % Ntrial = 20 ; Min = 64.865 + 3.235 clc/call; Median-Min = 3.475 clc/call; Max = 71.788 clc/call; -- System LIBC latency -- [####################] 100 % Ntrial = 20 ; Min = 42.151 + 2.090 clc/call; Median-Min = 2.270 clc/call; Max = 44.773 clc/call; -- LIBC latency -- with FMA [####################] 100 % Ntrial = 20 ; Min = 35.266 + 0.479 clc/call; Median-Min = 0.373 clc/call; Max = 36.798 clc/call; -- LIBC latency -- without FMA [####################] 100 % Ntrial = 20 ; Min = 48.518 + 0.484 clc/call; Median-Min = 0.500 clc/call; Max = 49.896 clc/call; ``` - Accurate pass latency: ``` $ ./perf.sh log --latency --simple_stat GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH latency -- with FMA 598.306 -- CORE-MATH latency -- without FMA (-march=x86-64-v2) 632.925 -- LIBC latency -- with FMA 455.632 -- LIBC latency -- without FMA 488.564 ``` Reviewed By: zimmermann6 Differential Revision: https://reviews.llvm.org/D150131
2023-05-23[libc][math] Make log10 correctly rounded for non-FMA targets and improve ↵Tue Ly
itsperformance. Make log10 correctly rounded for non-FMA targets and improve its performance. Implemented fast pass and accurate pass: **Fast Pass**: - Range reduction step 0: Extract exponent and mantissa ``` x = 2^(e_x) * m_x ``` - Range reduction step 1: Use lookup tables of size 2^7 = 128 to reduce the argument to: ``` -2^-8 <= v = r * m_x - 1 < 2^-7 where r = 2^-8 * ceil( 2^8 * (1 - 2^-8) / (1 + k * 2^-7) ) and k = trunc( (m_x - 1) * 2^7 ) ``` - Polynomial approximation: approximate `log(1 + v)` by a degree-7 polynomial generated by Sollya with: ``` > P = fpminimax((log(1 + x) - x)/x^2, 5, [|D...|], [-2^-8, 2^-7]); ``` - Combine the results: ``` log10(x) ~ ( e_x * log(2) - log(r) + v + v^2 * P(v) ) * log10(e) ``` - Perform additive Ziv's test with errors bounded by `P_ERR * v^2`. Return the result if Ziv's test passed. **Accurate Pass**: - Take `e_x`, `v`, and the lookup table index from the range reduction step of fast pass. - Perform 3 more range reduction steps: - Range reduction step 2: Use look-up tables of size 193 to reduce the argument to `[-0x1.3ffcp-15, 0x1.3e3dp-15]` ``` v2 = r2 * (1 + v) - 1 = (1 + s2) * (1 + v) - 1 = s2 + v + s2 * v where r2 = 2^-16 * round ( 2^16 / (1 + k * 2^-14) ) and k = trunc( v * 2^14 + 0.5 ). ``` - Range reduction step 3: Use look-up tables of size 161 to reduce the argument to `[-0x1.01928p-22 , 0x1p-22]` ``` v3 = r3 * (1 + v2) - 1 = (1 + s3) * (1 + v2) - 1 = s3 + v2 + s3 * v2 where r3 = 2^-21 * round ( 2^21 / (1 + k * 2^-21) ) and k = trunc( v * 2^21 + 0.5 ). ``` - Range reduction step 4: Use look-up tables of size 130 to reduce the argument to `[-0x1.0002143p-29 , 0x1p-29]` ``` v4 = r4 * (1 + v3) - 1 = (1 + s4) * (1 + v3) - 1 = s4 + v3 + s4 * v3 where r4 = 2^-28 * round ( 2^28 / (1 + k * 2^-28) ) and k = trunc( v * 2^28 + 0.5 ). ``` - Polynomial approximation: approximate `log10(1 + v4)` by a degree-4 minimax polynomial generated by Sollya with: ``` > P = fpminimax(log10(1 + x)/x, 3, [|128...|], [-0x1.0002143p-29 , 0x1p-29]); ``` - Combine the results: ``` log10(x) ~ e_x * log10(2) - log10(r) - log10(r2) - log10(r3) - log10(r4) + v * P(v) ``` - The combined results are computed using floating points of 128-bit precision. **Performance** - For `0.5 <= x <= 2`, the fast pass hitting rate is about 99.92%. - Reciprocal throughput from CORE-MATH's perf tool on Ryzen 5900X: ``` $ ./perf.sh log10 GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH reciprocal throughput -- with FMA [####################] 100 % Ntrial = 20 ; Min = 20.402 + 0.589 clc/call; Median-Min = 0.277 clc/call; Max = 22.752 clc/call; -- CORE-MATH reciprocal throughput -- without FMA (-march=x86-64-v2) [####################] 100 % Ntrial = 20 ; Min = 75.797 + 3.317 clc/call; Median-Min = 3.407 clc/call; Max = 79.371 clc/call; -- System LIBC reciprocal throughput -- [####################] 100 % Ntrial = 20 ; Min = 22.668 + 0.184 clc/call; Median-Min = 0.181 clc/call; Max = 23.205 clc/call; -- LIBC reciprocal throughput -- with FMA [####################] 100 % Ntrial = 20 ; Min = 25.977 + 0.183 clc/call; Median-Min = 0.138 clc/call; Max = 26.283 clc/call; -- LIBC reciprocal throughput -- without FMA [####################] 100 % Ntrial = 20 ; Min = 22.140 + 0.980 clc/call; Median-Min = 0.853 clc/call; Max = 23.790 clc/call; ``` - Latency from CORE-MATH's perf tool on Ryzen 5900X: ``` $ ./perf.sh log10 --latency GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH latency -- with FMA [####################] 100 % Ntrial = 20 ; Min = 54.613 + 0.357 clc/call; Median-Min = 0.287 clc/call; Max = 55.701 clc/call; -- CORE-MATH latency -- without FMA (-march=x86-64-v2) [####################] 100 % Ntrial = 20 ; Min = 79.681 + 0.482 clc/call; Median-Min = 0.294 clc/call; Max = 81.604 clc/call; -- System LIBC latency -- [####################] 100 % Ntrial = 20 ; Min = 61.532 + 0.208 clc/call; Median-Min = 0.199 clc/call; Max = 62.256 clc/call; -- LIBC latency -- with FMA [####################] 100 % Ntrial = 20 ; Min = 41.510 + 0.205 clc/call; Median-Min = 0.244 clc/call; Max = 41.867 clc/call; -- LIBC latency -- without FMA [####################] 100 % Ntrial = 20 ; Min = 55.669 + 0.240 clc/call; Median-Min = 0.280 clc/call; Max = 56.056 clc/call; ``` - Accurate pass latency: ``` $ ./perf.sh log10 --latency --simple_stat GNU libc version: 2.35 GNU libc release: stable -- CORE-MATH latency -- with FMA 640.688 -- CORE-MATH latency -- without FMA (-march=x86-64-v2) 667.354 -- LIBC latency -- with FMA 495.593 -- LIBC latency -- without FMA 504.143 ``` Reviewed By: zimmermann6 Differential Revision: https://reviews.llvm.org/D150014
2023-03-23[libc] Fix some math conversion warningsAlex Brachet
Differential Revision: https://reviews.llvm.org/D146738
2023-03-15[libc][NFC] Clean up clang-tidy warnings for `src/__support` and `src/math`.Tue Ly
Clean up some warnings from running libc-lint for these folders. Reviewed By: michaelrj, sivachandra Differential Revision: https://reviews.llvm.org/D146048
2023-03-07[libc][math] Switch math functions to use libc_errno and fix some errno and ↵Tue Ly
floating point exceptions. Switch math functions to use libc_errno and fix some errno and floating point exceptions Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D145349
2023-02-10[libc] Move likely/unlikely to the optimization headerGuillaume Chatelet
2023-02-07[libc][NFC] Move attributes from common to macros folderGuillaume Chatelet
2023-01-09[libc][Obvious] Address few GCC warnings.Siva Chandra Reddy
2023-01-08[libc][math] Implement log10 function correctly rounded for all rounding modesTue Ly
Implement double precision log10 function correctly rounded for all rounding modes. This implementation currently needs FMA instructions for correctness. Use 2 passes: Fast pass: - 1 step range reduction with a lookup table of `2^7 = 128` elements to reduce the ranges to `[-2^-7, 2^-7]`. - Use a degree-7 minimax polynomial generated by Sollya, evaluated using a mixed of double-double and double precisions. - Apply Ziv's test for accuracy. Accurate pass: - Apply 5 more range reduction steps to reduce the ranges further to [-2^-27, 2^-27]. - Use a degree-4 minimax polynomial generated by Sollya, evaluated using 192-bit precisions. - By the result of Lefevre (add quote), this is more than enough for correct rounding to all rounding modes. In progress: Adding detail documentations about the algorithm. Depend on: https://reviews.llvm.org/D136799 Reviewed By: zimmermann6 Differential Revision: https://reviews.llvm.org/D139846
generated by cgit v1.2.3 (git 2.25.1) at 2026-08-02 02:17:46 +0000