llvm-project/compiler-rt/README.txt

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Compiler-RT
================================
This directory and its subdirectories contain source code for the compiler
support routines.
Compiler-RT is open source software. You may freely distribute it under the
terms of the license agreement found in LICENSE.txt.
================================
This is a replacement library for libgcc. Each function is contained
in its own file. Each function has a corresponding unit test under
test/Unit.
A rudimentary script to test each file is in the file called
test/Unit/test.
Here is the specification for this library:
http://gcc.gnu.org/onlinedocs/gccint/Libgcc.html#Libgcc
Here is a synopsis of the contents of this library:
typedef int si_int;
typedef unsigned su_int;
typedef long long di_int;
typedef unsigned long long du_int;
// Integral bit manipulation
di_int __ashldi3(di_int a, si_int b); // a << b
di_int __ashrdi3(di_int a, si_int b); // a >> b arithmetic (sign fill)
di_int __lshrdi3(di_int a, si_int b); // a >> b logical (zero fill)
si_int __clzsi2(si_int a); // count leading zeros
si_int __clzdi2(di_int a); // count leading zeros
si_int __ctzsi2(si_int a); // count trailing zeros
si_int __ctzdi2(di_int a); // count trailing zeros
si_int __ffsdi2(di_int a); // find least significant 1 bit
si_int __paritysi2(si_int a); // bit parity
si_int __paritydi2(di_int a); // bit parity
si_int __popcountsi2(si_int a); // bit population
si_int __popcountdi2(di_int a); // bit population
// Integral arithmetic
di_int __negdi2 (di_int a); // -a
di_int __muldi3 (di_int a, di_int b); // a * b
di_int __divdi3 (di_int a, di_int b); // a / b signed
du_int __udivdi3 (du_int a, du_int b); // a / b unsigned
di_int __moddi3 (di_int a, di_int b); // a % b signed
du_int __umoddi3 (du_int a, du_int b); // a % b unsigned
du_int __udivmoddi4(du_int a, du_int b, du_int* rem); // a / b, *rem = a % b
// Integral arithmetic with trapping overflow
si_int __absvsi2(si_int a); // abs(a)
di_int __absvdi2(di_int a); // abs(a)
si_int __negvsi2(si_int a); // -a
di_int __negvdi2(di_int a); // -a
si_int __addvsi3(si_int a, si_int b); // a + b
di_int __addvdi3(di_int a, di_int b); // a + b
si_int __subvsi3(si_int a, si_int b); // a - b
di_int __subvdi3(di_int a, di_int b); // a - b
si_int __mulvsi3(si_int a, si_int b); // a * b
di_int __mulvdi3(di_int a, di_int b); // a * b
// Integral comparison: a < b -> 0
// a == b -> 1
// a > b -> 2
si_int __cmpdi2 (di_int a, di_int b);
si_int __ucmpdi2(du_int a, du_int b);
// Integral / floating point conversion
di_int __fixsfdi( float a);
di_int __fixdfdi( double a);
di_int __fixxfdi(long double a);
su_int __fixunssfsi( float a);
su_int __fixunsdfsi( double a);
su_int __fixunsxfsi(long double a);
du_int __fixunssfdi( float a);
du_int __fixunsdfdi( double a);
du_int __fixunsxfdi(long double a);
float __floatdisf(di_int a);
double __floatdidf(di_int a);
long double __floatdixf(di_int a);
float __floatundisf(du_int a);
double __floatundidf(du_int a);
long double __floatundixf(du_int a);
// Floating point raised to integer power
float __powisf2( float a, si_int b); // a ^ b
double __powidf2( double a, si_int b); // a ^ b
long double __powixf2(long double a, si_int b); // a ^ b
// Complex arithmetic
// (a + ib) * (c + id)
float _Complex __mulsc3( float a, float b, float c, float d);
double _Complex __muldc3(double a, double b, double c, double d);
long double _Complex __mulxc3(long double a, long double b,
long double c, long double d);
// (a + ib) / (c + id)
float _Complex __divsc3( float a, float b, float c, float d);
double _Complex __divdc3(double a, double b, double c, double d);
long double _Complex __divxc3(long double a, long double b,
long double c, long double d);
Preconditions are listed for each function at the definition when there are any.
Any preconditions reflect the specification at
http://gcc.gnu.org/onlinedocs/gccint/Libgcc.html#Libgcc.
Assumptions are listed in "int_lib.h", and in individual files. Where possible
assumptions are checked at compile time.