From 9a89611ae388867322bc6eecf0418016ab1d4686 Mon Sep 17 00:00:00 2001 From: Michael Jones Date: Wed, 2 Oct 2024 09:42:34 -0700 Subject: [PATCH] [libc] Enable dyadic float for float printf (#110765) Dyadic floats were an existing option for float to string conversion, but it had become stale. This patch fixes it up as well as adding proper config options and test support. Due to the test changes this is a followup to #110759 --- libc/config/config.json | 8 ++++++++ libc/docs/configure.rst | 2 ++ libc/src/__support/FPUtil/dyadic_float.h | 2 +- libc/src/__support/float_to_string.h | 19 +++++++++++-------- libc/src/stdio/printf_core/CMakeLists.txt | 6 ++++++ libc/test/src/stdio/CMakeLists.txt | 3 +++ libc/test/src/stdlib/CMakeLists.txt | 16 +++++++++++++--- libc/test/src/stdlib/StrfromTest.h | 4 ++++ 8 files changed, 48 insertions(+), 12 deletions(-) diff --git a/libc/config/config.json b/libc/config/config.json index caeb3e89a84d8d..2e4f878778e6e0 100644 --- a/libc/config/config.json +++ b/libc/config/config.json @@ -22,6 +22,14 @@ "value": false, "doc": "Use large table for better printf long double performance." }, + "LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT": { + "value": false, + "doc": "Use dyadic float for faster and smaller but less accurate printf doubles." + }, + "LIBC_CONF_PRINTF_FLOAT_TO_STR_NO_SPECIALIZE_LD": { + "value": false, + "doc": "Use the same mode for double and long double in printf." + }, "LIBC_CONF_PRINTF_DISABLE_FIXED_POINT": { "value": false, "doc": "Disable printing fixed point values in printf and friends." diff --git a/libc/docs/configure.rst b/libc/docs/configure.rst index c28d3a36ada748..867bb807d10ac9 100644 --- a/libc/docs/configure.rst +++ b/libc/docs/configure.rst @@ -40,6 +40,8 @@ to learn about the defaults for your platform and target. - ``LIBC_CONF_PRINTF_DISABLE_INDEX_MODE``: Disable index mode in the printf format string. - ``LIBC_CONF_PRINTF_DISABLE_STRERROR``: Disable handling of %m to print strerror in printf and friends. - ``LIBC_CONF_PRINTF_DISABLE_WRITE_INT``: Disable handling of %n in printf format string. + - ``LIBC_CONF_PRINTF_FLOAT_TO_STR_NO_SPECIALIZE_LD``: Use the same mode for double and long double in printf. + - ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT``: Use dyadic float for faster and smaller but less accurate printf doubles. - ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE``: Use large table for better printf long double performance. * **"pthread" options** - ``LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT``: Default number of spins before blocking if a mutex is in contention (default to 100). diff --git a/libc/src/__support/FPUtil/dyadic_float.h b/libc/src/__support/FPUtil/dyadic_float.h index 165ffc7c922025..289fd01680547d 100644 --- a/libc/src/__support/FPUtil/dyadic_float.h +++ b/libc/src/__support/FPUtil/dyadic_float.h @@ -357,7 +357,7 @@ template struct DyadicFloat { return as(); } - LIBC_INLINE explicit constexpr operator MantissaType() const { + LIBC_INLINE constexpr MantissaType as_mantissa_type() const { if (mantissa.is_zero()) return 0; diff --git a/libc/src/__support/float_to_string.h b/libc/src/__support/float_to_string.h index c4c7a15179f95c..e2e06cd0492a90 100644 --- a/libc/src/__support/float_to_string.h +++ b/libc/src/__support/float_to_string.h @@ -20,6 +20,7 @@ #include "src/__support/libc_assert.h" #include "src/__support/macros/attributes.h" #include "src/__support/macros/config.h" +#include "src/__support/sign.h" // This file has 5 compile-time flags to allow the user to configure the float // to string behavior. These were used to explore tradeoffs during the design @@ -232,7 +233,7 @@ LIBC_INLINE UInt get_table_positive_df(int exponent, size_t i) { if (shift_amount < 0) { return 1; } - fputil::DyadicFloat num(false, 0, 1); + fputil::DyadicFloat num(Sign::POS, 0, 1); constexpr UInt MOD_SIZE = (UInt(EXP10_9) << (CALC_SHIFT_CONST + (IDX_SIZE > 1 ? IDX_SIZE : 0))); @@ -242,16 +243,17 @@ LIBC_INLINE UInt get_table_positive_df(int exponent, size_t i) { 0x89705f4136b4a597}}; static const fputil::DyadicFloat FIVE_EXP_MINUS_NINE( - false, -276, FIVE_EXP_MINUS_NINE_MANT); + Sign::POS, -276, FIVE_EXP_MINUS_NINE_MANT); if (i > 0) { - fputil::DyadicFloat fives = fputil::pow_n(FIVE_EXP_MINUS_NINE, i); + fputil::DyadicFloat fives = + fputil::pow_n(FIVE_EXP_MINUS_NINE, static_cast(i)); num = fives; } num = mul_pow_2(num, shift_amount); // Adding one is part of the formula. - UInt int_num = static_cast>(num) + 1; + UInt int_num = num.as_mantissa_type() + 1; if (int_num > MOD_SIZE) { auto rem = int_num @@ -339,23 +341,24 @@ LIBC_INLINE UInt get_table_negative_df(int exponent, size_t i) { int shift_amount = CALC_SHIFT_CONST - exponent; - fputil::DyadicFloat num(false, 0, 1); + fputil::DyadicFloat num(Sign::POS, 0, 1); constexpr UInt MOD_SIZE = (UInt(EXP10_9) << (CALC_SHIFT_CONST + (IDX_SIZE > 1 ? IDX_SIZE : 0))); constexpr UInt TEN_EXP_NINE_MANT(EXP10_9); - static const fputil::DyadicFloat TEN_EXP_NINE(false, 0, + static const fputil::DyadicFloat TEN_EXP_NINE(Sign::POS, 0, TEN_EXP_NINE_MANT); if (i > 0) { - fputil::DyadicFloat tens = fputil::pow_n(TEN_EXP_NINE, i); + fputil::DyadicFloat tens = + fputil::pow_n(TEN_EXP_NINE, static_cast(i)); num = tens; } num = mul_pow_2(num, shift_amount); - UInt int_num = static_cast>(num); + UInt int_num = num.as_mantissa_type(); if (int_num > MOD_SIZE) { auto rem = int_num diff --git a/libc/src/stdio/printf_core/CMakeLists.txt b/libc/src/stdio/printf_core/CMakeLists.txt index 542327ad5a49a9..8172fda1e866ed 100644 --- a/libc/src/stdio/printf_core/CMakeLists.txt +++ b/libc/src/stdio/printf_core/CMakeLists.txt @@ -10,6 +10,12 @@ endif() if(LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE) list(APPEND printf_config_copts "-DLIBC_COPT_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE") endif() +if(LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT) + list(APPEND printf_config_copts "-DLIBC_COPT_FLOAT_TO_STR_USE_DYADIC_FLOAT") +endif() +if(LIBC_CONF_PRINTF_FLOAT_TO_STR_NO_SPECIALIZE_LD) + list(APPEND printf_config_copts "-DLIBC_COPT_FLOAT_TO_STR_NO_SPECIALIZE_LD") +endif() if(LIBC_CONF_PRINTF_DISABLE_FIXED_POINT) list(APPEND printf_config_copts "-DLIBC_COPT_PRINTF_DISABLE_FIXED_POINT") endif() diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt index e970e4cf014052..ec94f5aaaf9b62 100644 --- a/libc/test/src/stdio/CMakeLists.txt +++ b/libc/test/src/stdio/CMakeLists.txt @@ -116,6 +116,9 @@ add_libc_test( if(LIBC_CONF_PRINTF_DISABLE_FLOAT) list(APPEND sprintf_test_copts "-DLIBC_COPT_PRINTF_DISABLE_FLOAT") endif() +if(LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT) + list(APPEND sprintf_test_copts "-DLIBC_COPT_FLOAT_TO_STR_REDUCED_PRECISION") +endif() if(LIBC_CONF_PRINTF_DISABLE_INDEX_MODE) list(APPEND sprintf_test_copts "-DLIBC_COPT_PRINTF_DISABLE_INDEX_MODE") endif() diff --git a/libc/test/src/stdlib/CMakeLists.txt b/libc/test/src/stdlib/CMakeLists.txt index db90d9a4741ebf..c68627a6687419 100644 --- a/libc/test/src/stdlib/CMakeLists.txt +++ b/libc/test/src/stdlib/CMakeLists.txt @@ -168,13 +168,17 @@ add_libc_test( .strtol_test_support ) +if(LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT) + list(APPEND strfrom_test_copts "-DLIBC_COPT_FLOAT_TO_STR_REDUCED_PRECISION") +endif() + add_header_library( strfrom_test_support HDRS - StrfromTest.h + StrfromTest.h DEPENDS - libc.src.__support.CPP.type_traits - libc.src.__support.FPUtil.fp_bits + libc.src.__support.CPP.type_traits + libc.src.__support.FPUtil.fp_bits ) add_libc_test( @@ -186,6 +190,8 @@ add_libc_test( DEPENDS .strfrom_test_support libc.src.stdlib.strfromf + COMPILE_OPTIONS + ${strfrom_test_copts} ) add_libc_test( @@ -197,6 +203,8 @@ add_libc_test( DEPENDS .strfrom_test_support libc.src.stdlib.strfromd + COMPILE_OPTIONS + ${strfrom_test_copts} ) add_libc_test( @@ -208,6 +216,8 @@ add_libc_test( DEPENDS .strfrom_test_support libc.src.stdlib.strfroml + COMPILE_OPTIONS + ${strfrom_test_copts} ) add_libc_test( diff --git a/libc/test/src/stdlib/StrfromTest.h b/libc/test/src/stdlib/StrfromTest.h index 0db507ef0716e9..5209472886f78e 100644 --- a/libc/test/src/stdlib/StrfromTest.h +++ b/libc/test/src/stdlib/StrfromTest.h @@ -156,6 +156,9 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test { written = func(buff, 99, "%f", 1.5); ASSERT_STREQ_LEN(written, buff, "1.500000"); +// Dyadic float is only accurate to ~50 digits, so skip this 300 digit test. +// TODO: Create way to test just the first ~50 digits of a number. +#ifndef LIBC_COPT_FLOAT_TO_STR_REDUCED_PRECISION written = func(buff, 499, "%f", 1e300); ASSERT_STREQ_LEN(written, buff, "100000000000000005250476025520442024870446858110815915491" @@ -167,6 +170,7 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test { "111903896764088007465274278014249457925878882005684283811" "566947219638686" "5459400540160.000000"); +#endif // DLIBC_COPT_FLOAT_TO_STR_REDUCED_PRECISION written = func(buff, 99, "%f", 0.1); ASSERT_STREQ_LEN(written, buff, "0.100000");