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Marcus Holland-Moritz authored
Summary: This is the main diff of the series. Its main purpose is to make the internals of folly::to<> propagate error codes instead of throwing exceptions. Along with this, it makes the following changes: - Move most of the string-to-int implementation out of the header file - Unify error/exception strings across conversion routines - Introduce a ConversionError class that derives from std::range_error - Capture an error code in ConversionError in addition to a string - Optimize tolower() calls in Conv.cpp - Introduce ConversionResult<>, which is used as the internal result wrapper - Get rid of all error checking macros There are quite a few benefits here. == Faster conversions == For a large set of conversions, the performance is unchanged. I've removed all benchmarks that were unchanged from the table below for simplicity. A few things stand out: - `follyAtoiMeasure` is consistently faster, sometimes by quite a large margin - The cost of throwing exceptions is significantly reduced, as throwing them further down on the call stack will reduce the amount of stack unwinding - String-to-boolean and string-to-float conversions are significantly faster when passing in a string representation (e.g. "off" or "infinity") thanks to the optimized tolower_ascii() call (column `New+Ascii` in the table) - Conversions between int and float are significantly faster and almost back at the performance of before the undefined behaviour fix - All string-to-(int|float|bool) conversions are consistently faster The columns in the table are as follows: Original: Original code before the undefined behaviour fix Fix UB: Code with the undefined behaviour fix; this impacts mostly the float <-> int conversions, but appears to have a small effect on some other benchmarks New: New code introduced by this diff, but without the tolower_ascii() optimization New+Ascii: New code, including the tolower_ascii() optimization =========================================================================================== Original Fix UB New New+Ascii folly/test/ConvBenchmark.cpp time/iter time/iter time/iter time/iter =========================================================================================== handwrittenAtoiMeasure(1) 3.95ns 3.95ns 3.95ns 3.95ns follyAtoiMeasure(1) 6.08ns 6.08ns 3.95ns 3.95ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(2) 5.47ns 5.47ns 5.47ns 5.47ns follyAtoiMeasure(2) 5.77ns 5.77ns 3.95ns 3.95ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(3) 6.08ns 6.08ns 6.08ns 6.08ns follyAtoiMeasure(3) 6.08ns 6.08ns 4.25ns 4.25ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(4) 6.99ns 6.99ns 6.99ns 6.99ns follyAtoiMeasure(4) 6.99ns 6.99ns 4.56ns 4.56ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(5) 7.90ns 8.20ns 7.90ns 7.90ns follyAtoiMeasure(5) 7.29ns 7.29ns 4.86ns 4.86ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(6) 8.81ns 9.42ns 8.81ns 8.81ns follyAtoiMeasure(6) 7.29ns 7.29ns 4.86ns 4.86ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(7) 9.72ns 10.63ns 9.72ns 9.72ns follyAtoiMeasure(7) 7.60ns 7.60ns 5.16ns 5.16ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(8) 10.63ns 11.85ns 10.63ns 10.63ns follyAtoiMeasure(8) 8.51ns 8.51ns 6.08ns 6.08ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(9) 11.54ns 13.07ns 11.54ns 11.54ns follyAtoiMeasure(9) 8.81ns 8.81ns 6.08ns 6.08ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(10) 12.46ns 14.28ns 12.46ns 12.46ns follyAtoiMeasure(10) 8.81ns 8.81ns 6.38ns 6.38ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(11) 13.37ns 15.50ns 13.37ns 13.37ns follyAtoiMeasure(11) 9.12ns 9.12ns 6.38ns 6.38ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(12) 14.28ns 16.71ns 14.28ns 14.28ns follyAtoiMeasure(12) 10.03ns 10.03ns 7.29ns 7.29ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(13) 15.19ns 17.92ns 15.19ns 15.19ns follyAtoiMeasure(13) 10.33ns 10.33ns 7.60ns 7.60ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(14) 16.10ns 19.14ns 16.10ns 16.10ns follyAtoiMeasure(14) 10.33ns 10.33ns 7.60ns 7.60ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(15) 17.01ns 20.36ns 17.01ns 17.01ns follyAtoiMeasure(15) 10.63ns 10.63ns 7.90ns 7.90ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(16) 17.92ns 21.57ns 17.92ns 17.92ns follyAtoiMeasure(16) 11.55ns 11.55ns 8.81ns 8.81ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(17) 18.84ns 22.79ns 18.84ns 18.84ns follyAtoiMeasure(17) 11.85ns 11.85ns 8.81ns 8.81ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(18) 19.75ns 24.00ns 19.75ns 19.75ns follyAtoiMeasure(18) 11.85ns 11.85ns 9.12ns 9.12ns ------------------------------------------------------------------------------------------- handwrittenAtoiMeasure(19) 20.66ns 25.22ns 20.66ns 20.66ns follyAtoiMeasure(19) 12.16ns 12.16ns 9.11ns 9.11ns ------------------------------------------------------------------------------------------- stringToBoolNumClassic 12.76ns 12.76ns 11.96ns 12.15ns stringToBoolNumClassicError 3.19us 3.18us 1.58us 1.58us stringToBoolStrClassic 17.92ns 17.92ns 15.50ns 7.60ns stringToBoolStrClassicError 3.21us 3.18us 1.57us 1.57us ------------------------------------------------------------------------------------------- stringToFloatNumClassic 32.96ns 32.81ns 32.10ns 31.12ns stringToFloatNumClassicError 2.73us 2.69us 1.65us 1.66us stringToFloatStrClassic 37.37ns 38.58ns 36.76ns 16.71ns stringToFloatStrClassicError 2.87us 2.87us 1.60us 1.59us stringToDoubleNumClassic 31.30ns 31.82ns 29.77ns 29.17ns stringToDoubleNumClassicError 2.69us 2.66us 1.65us 1.66us stringToDoubleStrClassic 37.67ns 37.67ns 35.84ns 16.71ns stringToDoubleStrClassicError 2.87us 2.86us 1.58us 1.58us ------------------------------------------------------------------------------------------- stringToCharSignedClassic 16.71ns 18.08ns 15.49ns 14.59ns stringToCharSignedClassicError 3.87us 3.82us 1.61us 1.61us stringToCharUnsignedClassic 15.49ns 15.19ns 12.46ns 12.66ns stringToCharUnsignedClassicError 2.73us 2.70us 1.62us 1.62us stringToIntSignedClassic 21.26ns 19.44ns 17.92ns 18.40ns stringToIntSignedClassicError 3.94us 3.89us 1.64us 1.64us stringToIntUnsignedClassic 17.93ns 18.53ns 15.50ns 15.50ns stringToIntUnsignedClassicError 2.72us 2.71us 1.62us 1.61us stringToLongLongSignedClassic 34.63ns 30.58ns 27.04ns 27.04ns stringToLongLongSignedClassicError 3.94us 3.90us 1.63us 1.63us stringToLongLongUnsignedClassic 51.04ns 47.96ns 46.44ns 46.68ns stringToLongLongUnsignedClassicError 2.73us 2.71us 1.61us 1.61us ------------------------------------------------------------------------------------------- ptrPairToCharSignedClassic 5.16ns 5.16ns 3.34ns 3.65ns ptrPairToCharSignedClassicError 3.56us 3.54us 1.61us 1.61us ptrPairToCharUnsignedClassic 2.43ns 2.43ns 2.13ns 2.13ns ptrPairToCharUnsignedClassicError 2.63us 2.63us 1.61us 1.61us ptrPairToIntSignedClassic 6.99ns 6.99ns 5.16ns 5.16ns ptrPairToIntSignedClassicError 4.08us 4.06us 1.61us 1.61us ptrPairToIntUnsignedClassic 4.25ns 4.56ns 3.34ns 3.34ns ptrPairToIntUnsignedClassicError 2.70us 2.70us 1.60us 1.60us ptrPairToLongLongSignedClassic 12.16ns 12.16ns 9.72ns 9.72ns ptrPairToLongLongSignedClassicError 4.06us 4.06us 1.61us 1.61us ptrPairToLongLongUnsignedClassic 29.13ns 29.13ns 27.61ns 27.61ns ptrPairToLongLongUnsignedClassicError 2.71us 2.72us 1.63us 1.64us ------------------------------------------------------------------------------------------- intToCharSignedClassic 405.02ps 506.35ps 405.02ps 405.02ps intToCharSignedClassicError 2.10us 2.09us 1.63us 1.64us intToCharUnsignedClassic 303.79ps 303.78ps 303.77ps 303.77ps intToCharUnsignedClassicError 2.10us 2.09us 1.63us 1.64us intToIntSignedClassic 405.02ps 405.02ps 405.01ps 405.01ps intToIntSignedClassicError 1.99us 1.98us 1.72us 1.72us intToIntUnsignedClassic 405.03ps 405.03ps 379.71ps 379.71ps intToIntUnsignedClassicError 2.09us 2.09us 1.63us 1.63us ------------------------------------------------------------------------------------------- intToFloatClassic 545.11ps 3.34ns 1.23ns 1.23ns intToFloatClassicError 1.67us 2.37us 1.73us 1.72us ------------------------------------------------------------------------------------------- floatToFloatClassic 759.47ps 759.47ps 759.45ps 759.45ps floatToFloatClassicError 6.45us 6.44us 1.77us 1.77us ------------------------------------------------------------------------------------------- floatToIntClassic 637.82ps 2.89ns 1.50ns 1.50ns floatToIntClassicError 1.92us 2.61us 1.82us 1.83us =========================================================================================== == Improved build times == I've checked this with gcc 4.9.3, and compile times for both ConvTest and ConvBenchmark are reduced by roughly 10%: ==================================== original new code ------------------------------------ ConvTest.o 14.788s 13.361s ConvBenchmark.o 16.148s 14.578s ==================================== == Smaller binary size == Again, checked with gcc 4.9.3, stripped binaries are slightly smaller with the new code: ==================================== original new code ------------------------------------ conv_test 761704 749384 conv_benchmark 539632 510928 ==================================== == Ability to add new non-throwing interfaces == This change sticks to the original API that will throw an exception in case of an error. A subsequent diff will introduce non-throwing interfaces with a minimum of additional code. Reviewed By: ericniebler Differential Revision: D3433856 fbshipit-source-id: 9bc976ebc181fe2f172ae47c78edf407e9ee7bb0ad2f872b
