diff options
Diffstat (limited to 'arch/arm/lib/uldivmod.S')
| -rw-r--r-- | arch/arm/lib/uldivmod.S | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/arch/arm/lib/uldivmod.S b/arch/arm/lib/uldivmod.S new file mode 100644 index 0000000000..724699658b --- /dev/null +++ b/arch/arm/lib/uldivmod.S @@ -0,0 +1,246 @@ +/* + * Copyright 2010, Google Inc. + * + * Brought in from coreboot uldivmod.S + * + * SPDX-License-Identifier: GPL-2.0 + */ + +#include <linux/linkage.h> +#include <asm/assembler.h> + +/* + * A, Q = r0 + (r1 << 32) + * B, R = r2 + (r3 << 32) + * A / B = Q ... R + */ + +A_0 .req r0 +A_1 .req r1 +B_0 .req r2 +B_1 .req r3 +C_0 .req r4 +C_1 .req r5 +D_0 .req r6 +D_1 .req r7 + +Q_0 .req r0 +Q_1 .req r1 +R_0 .req r2 +R_1 .req r3 + +THUMB( +TMP .req r8 +) + +.pushsection .text.__aeabi_uldivmod, "ax" +ENTRY(__aeabi_uldivmod) + + stmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) lr} + @ Test if B == 0 + orrs ip, B_0, B_1 @ Z set -> B == 0 + beq L_div_by_0 + @ Test if B is power of 2: (B & (B - 1)) == 0 + subs C_0, B_0, #1 + sbc C_1, B_1, #0 + tst C_0, B_0 + tsteq B_1, C_1 + beq L_pow2 + @ Test if A_1 == B_1 == 0 + orrs ip, A_1, B_1 + beq L_div_32_32 + +L_div_64_64: +/* CLZ only exists in ARM architecture version 5 and above. */ +#ifdef HAVE_CLZ + mov C_0, #1 + mov C_1, #0 + @ D_0 = clz A + teq A_1, #0 + clz D_0, A_1 + clzeq ip, A_0 + addeq D_0, D_0, ip + @ D_1 = clz B + teq B_1, #0 + clz D_1, B_1 + clzeq ip, B_0 + addeq D_1, D_1, ip + @ if clz B - clz A > 0 + subs D_0, D_1, D_0 + bls L_done_shift + @ B <<= (clz B - clz A) + subs D_1, D_0, #32 + rsb ip, D_0, #32 + movmi B_1, B_1, lsl D_0 +ARM( orrmi B_1, B_1, B_0, lsr ip ) +THUMB( lsrmi TMP, B_0, ip ) +THUMB( orrmi B_1, B_1, TMP ) + movpl B_1, B_0, lsl D_1 + mov B_0, B_0, lsl D_0 + @ C = 1 << (clz B - clz A) + movmi C_1, C_1, lsl D_0 +ARM( orrmi C_1, C_1, C_0, lsr ip ) +THUMB( lsrmi TMP, C_0, ip ) +THUMB( orrmi C_1, C_1, TMP ) + movpl C_1, C_0, lsl D_1 + mov C_0, C_0, lsl D_0 +L_done_shift: + mov D_0, #0 + mov D_1, #0 + @ C: current bit; D: result +#else + @ C: current bit; D: result + mov C_0, #1 + mov C_1, #0 + mov D_0, #0 + mov D_1, #0 +L_lsl_4: + cmp B_1, #0x10000000 + cmpcc B_1, A_1 + cmpeq B_0, A_0 + bcs L_lsl_1 + @ B <<= 4 + mov B_1, B_1, lsl #4 + orr B_1, B_1, B_0, lsr #28 + mov B_0, B_0, lsl #4 + @ C <<= 4 + mov C_1, C_1, lsl #4 + orr C_1, C_1, C_0, lsr #28 + mov C_0, C_0, lsl #4 + b L_lsl_4 +L_lsl_1: + cmp B_1, #0x80000000 + cmpcc B_1, A_1 + cmpeq B_0, A_0 + bcs L_subtract + @ B <<= 1 + mov B_1, B_1, lsl #1 + orr B_1, B_1, B_0, lsr #31 + mov B_0, B_0, lsl #1 + @ C <<= 1 + mov C_1, C_1, lsl #1 + orr C_1, C_1, C_0, lsr #31 + mov C_0, C_0, lsl #1 + b L_lsl_1 +#endif +L_subtract: + @ if A >= B + cmp A_1, B_1 + cmpeq A_0, B_0 + bcc L_update + @ A -= B + subs A_0, A_0, B_0 + sbc A_1, A_1, B_1 + @ D |= C + orr D_0, D_0, C_0 + orr D_1, D_1, C_1 +L_update: + @ if A == 0: break + orrs ip, A_1, A_0 + beq L_exit + @ C >>= 1 + movs C_1, C_1, lsr #1 + movs C_0, C_0, rrx + @ if C == 0: break + orrs ip, C_1, C_0 + beq L_exit + @ B >>= 1 + movs B_1, B_1, lsr #1 + mov B_0, B_0, rrx + b L_subtract +L_exit: + @ Note: A, B & Q, R are aliases + mov R_0, A_0 + mov R_1, A_1 + mov Q_0, D_0 + mov Q_1, D_1 + ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc} + +L_div_32_32: + @ Note: A_0 & r0 are aliases + @ Q_1 r1 + mov r1, B_0 + bl __aeabi_uidivmod + mov R_0, r1 + mov R_1, #0 + mov Q_1, #0 + ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc} + +L_pow2: +#ifdef HAVE_CLZ + @ Note: A, B and Q, R are aliases + @ R = A & (B - 1) + and C_0, A_0, C_0 + and C_1, A_1, C_1 + @ Q = A >> log2(B) + @ Note: B must not be 0 here! + clz D_0, B_0 + add D_1, D_0, #1 + rsbs D_0, D_0, #31 + bpl L_1 + clz D_0, B_1 + rsb D_0, D_0, #31 + mov A_0, A_1, lsr D_0 + add D_0, D_0, #32 +L_1: + movpl A_0, A_0, lsr D_0 +ARM( orrpl A_0, A_0, A_1, lsl D_1 ) +THUMB( lslpl TMP, A_1, D_1 ) +THUMB( orrpl A_0, A_0, TMP ) + mov A_1, A_1, lsr D_0 + @ Mov back C to R + mov R_0, C_0 + mov R_1, C_1 + ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc} +#else + @ Note: A, B and Q, R are aliases + @ R = A & (B - 1) + and C_0, A_0, C_0 + and C_1, A_1, C_1 + @ Q = A >> log2(B) + @ Note: B must not be 0 here! + @ Count the leading zeroes in B. + mov D_0, #0 + orrs B_0, B_0, B_0 + @ If B is greater than 1 << 31, divide A and B by 1 << 32. + moveq A_0, A_1 + moveq A_1, #0 + moveq B_0, B_1 + @ Count the remaining leading zeroes in B. + movs B_1, B_0, lsl #16 + addeq D_0, #16 + moveq B_0, B_0, lsr #16 + tst B_0, #0xff + addeq D_0, #8 + moveq B_0, B_0, lsr #8 + tst B_0, #0xf + addeq D_0, #4 + moveq B_0, B_0, lsr #4 + tst B_0, #0x3 + addeq D_0, #2 + moveq B_0, B_0, lsr #2 + tst B_0, #0x1 + addeq D_0, #1 + @ Shift A to the right by the appropriate amount. + rsb D_1, D_0, #32 + mov Q_0, A_0, lsr D_0 + ARM( orr Q_0, Q_0, A_1, lsl D_1 ) + THUMB( lsl A_1, D_1 ) + THUMB( orr Q_0, A_1 ) + mov Q_1, A_1, lsr D_0 + @ Move C to R + mov R_0, C_0 + mov R_1, C_1 + ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc} +#endif + +L_div_by_0: + bl __div0 + @ As wrong as it could be + mov Q_0, #0 + mov Q_1, #0 + mov R_0, #0 + mov R_1, #0 + ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc} +ENDPROC(__aeabi_uldivmod) +.popsection |