diff options
Diffstat (limited to 'contrib/compiler-rt/lib/arm/modsi3.S')
| -rw-r--r-- | contrib/compiler-rt/lib/arm/modsi3.S | 67 |
1 files changed, 35 insertions, 32 deletions
diff --git a/contrib/compiler-rt/lib/arm/modsi3.S b/contrib/compiler-rt/lib/arm/modsi3.S index 64a3afd..a4cd2ee 100644 --- a/contrib/compiler-rt/lib/arm/modsi3.S +++ b/contrib/compiler-rt/lib/arm/modsi3.S @@ -1,36 +1,39 @@ -//===-------- modsi3.S - Implement modsi3 ---------------------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// +/*===-- modsi3.S - 32-bit signed integer modulus --------------------------===// + * + * The LLVM Compiler Infrastructure + * + * This file is dual licensed under the MIT and the University of Illinois Open + * Source Licenses. See LICENSE.TXT for details. + * + *===----------------------------------------------------------------------===// + * + * This file implements the __modsi3 (32-bit signed integer modulus) function + * for the ARM architecture as a wrapper around the unsigned routine. + * + *===----------------------------------------------------------------------===*/ #include "../assembly.h" -// -// extern int32_t __modsi3(int32_t a, int32_t b); -// -// Returns the remainder when dividing two 32-bit signed integers. -// Conceptually, the function is: { return a - (a / b) * b; } -// But if you write that in C, llvm compiles it to a call to __modsi3... -// - .align 2 -DEFINE_COMPILERRT_FUNCTION(__modsi3) - push {r4, r5, r7, lr} - add r7, sp, #8 // set stack frame - mov r5, r0 // save a - mov r4, r1 // save b - bl ___divsi3 // compute a/b -#if __ARM_ARCH_7A__ - mls r0, r4, r0, r5 // mulitple result * b and subtract from a -#else - // before armv7, does not have "mls" instruction - mul r3, r0, r4 // multiple result * b - sub r0, r5, r3 // a - result -#endif - pop {r4, r5, r7, pc} - - +#define ESTABLISH_FRAME \ + push {r4, r7, lr} ;\ + add r7, sp, #4 +#define CLEAR_FRAME_AND_RETURN \ + pop {r4, r7, pc} +.syntax unified +.align 3 +DEFINE_COMPILERRT_FUNCTION(__modsi3) + ESTABLISH_FRAME + // Set aside the sign of the dividend. + mov r4, r0 + // Take absolute value of a and b via abs(x) = (x^(x >> 31)) - (x >> 31). + eor r2, r0, r0, asr #31 + eor r3, r1, r1, asr #31 + sub r0, r2, r0, asr #31 + sub r1, r3, r1, asr #31 + // abs(a) % abs(b) + bl SYMBOL_NAME(__umodsi3) + // Apply sign of dividend to result and return. + eor r0, r0, r4, asr #31 + sub r0, r0, r4, asr #31 + CLEAR_FRAME_AND_RETURN |
