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Diffstat (limited to 'lib/builtins/arm/udivmodsi4.S')
| -rw-r--r-- | lib/builtins/arm/udivmodsi4.S | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/lib/builtins/arm/udivmodsi4.S b/lib/builtins/arm/udivmodsi4.S new file mode 100644 index 000000000000..85b84936c4b3 --- /dev/null +++ b/lib/builtins/arm/udivmodsi4.S @@ -0,0 +1,184 @@ +/*===-- udivmodsi4.S - 32-bit unsigned integer divide and 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 __udivmodsi4 (32-bit unsigned integer divide and + * modulus) function for the ARM 32-bit architecture. + * + *===----------------------------------------------------------------------===*/ + +#include "../assembly.h" + + .syntax unified + .text + +#if __ARM_ARCH_ISA_THUMB == 2 + .thumb +#endif + +@ unsigned int __udivmodsi4(unsigned int divident, unsigned int divisor, +@ unsigned int *remainder) +@ Calculate the quotient and remainder of the (unsigned) division. The return +@ value is the quotient, the remainder is placed in the variable. + + .p2align 2 +#if __ARM_ARCH_ISA_THUMB == 2 +DEFINE_COMPILERRT_THUMB_FUNCTION(__udivmodsi4) +#else +DEFINE_COMPILERRT_FUNCTION(__udivmodsi4) +#endif +#if __ARM_ARCH_EXT_IDIV__ + tst r1, r1 + beq LOCAL_LABEL(divby0) + mov r3, r0 + udiv r0, r3, r1 + mls r1, r0, r1, r3 + str r1, [r2] + bx lr +#else + cmp r1, #1 + bcc LOCAL_LABEL(divby0) + beq LOCAL_LABEL(divby1) + cmp r0, r1 + bcc LOCAL_LABEL(quotient0) + /* + * Implement division using binary long division algorithm. + * + * r0 is the numerator, r1 the denominator. + * + * The code before JMP computes the correct shift I, so that + * r0 and (r1 << I) have the highest bit set in the same position. + * At the time of JMP, ip := .Ldiv0block - 12 * I. + * This depends on the fixed instruction size of block. + * For ARM mode, this is 12 Bytes, for THUMB mode 14 Bytes. + * + * block(shift) implements the test-and-update-quotient core. + * It assumes (r0 << shift) can be computed without overflow and + * that (r0 << shift) < 2 * r1. The quotient is stored in r3. + */ + +# ifdef __ARM_FEATURE_CLZ + clz ip, r0 + clz r3, r1 + /* r0 >= r1 implies clz(r0) <= clz(r1), so ip <= r3. */ + sub r3, r3, ip +# if __ARM_ARCH_ISA_THUMB == 2 + adr ip, LOCAL_LABEL(div0block) + 1 + sub ip, ip, r3, lsl #1 +# else + adr ip, LOCAL_LABEL(div0block) +# endif + sub ip, ip, r3, lsl #2 + sub ip, ip, r3, lsl #3 + mov r3, #0 + bx ip +# else +# if __ARM_ARCH_ISA_THUMB == 2 +# error THUMB mode requires CLZ or UDIV +# endif + str r4, [sp, #-8]! + + mov r4, r0 + adr ip, LOCAL_LABEL(div0block) + + lsr r3, r4, #16 + cmp r3, r1 + movhs r4, r3 + subhs ip, ip, #(16 * 12) + + lsr r3, r4, #8 + cmp r3, r1 + movhs r4, r3 + subhs ip, ip, #(8 * 12) + + lsr r3, r4, #4 + cmp r3, r1 + movhs r4, r3 + subhs ip, #(4 * 12) + + lsr r3, r4, #2 + cmp r3, r1 + movhs r4, r3 + subhs ip, ip, #(2 * 12) + + /* Last block, no need to update r3 or r4. */ + cmp r1, r4, lsr #1 + subls ip, ip, #(1 * 12) + + ldr r4, [sp], #8 /* restore r4, we are done with it. */ + mov r3, #0 + + JMP(ip) +# endif + +#define IMM # + +#define block(shift) \ + cmp r0, r1, lsl IMM shift; \ + ITT(hs); \ + WIDE(addhs) r3, r3, IMM (1 << shift); \ + WIDE(subhs) r0, r0, r1, lsl IMM shift + + block(31) + block(30) + block(29) + block(28) + block(27) + block(26) + block(25) + block(24) + block(23) + block(22) + block(21) + block(20) + block(19) + block(18) + block(17) + block(16) + block(15) + block(14) + block(13) + block(12) + block(11) + block(10) + block(9) + block(8) + block(7) + block(6) + block(5) + block(4) + block(3) + block(2) + block(1) +LOCAL_LABEL(div0block): + block(0) + + str r0, [r2] + mov r0, r3 + JMP(lr) + +LOCAL_LABEL(quotient0): + str r0, [r2] + mov r0, #0 + JMP(lr) + +LOCAL_LABEL(divby1): + mov r3, #0 + str r3, [r2] + JMP(lr) +#endif /* __ARM_ARCH_EXT_IDIV__ */ + +LOCAL_LABEL(divby0): + mov r0, #0 +#ifdef __ARM_EABI__ + b __aeabi_idiv0 +#else + JMP(lr) +#endif + +END_COMPILERRT_FUNCTION(__udivmodsi4) |