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Diffstat (limited to 'sysdeps/sparc/sparc32/divrem.m4')
| -rw-r--r-- | sysdeps/sparc/sparc32/divrem.m4 | 234 |
1 files changed, 0 insertions, 234 deletions
diff --git a/sysdeps/sparc/sparc32/divrem.m4 b/sysdeps/sparc/sparc32/divrem.m4 deleted file mode 100644 index c08c530020..0000000000 --- a/sysdeps/sparc/sparc32/divrem.m4 +++ /dev/null @@ -1,234 +0,0 @@ -/* - * Division and remainder, from Appendix E of the Sparc Version 8 - * Architecture Manual, with fixes from Gordon Irlam. - */ - -/* - * Input: dividend and divisor in %o0 and %o1 respectively. - * - * m4 parameters: - * NAME name of function to generate - * OP OP=div => %o0 / %o1; OP=rem => %o0 % %o1 - * S S=true => signed; S=false => unsigned - * - * Algorithm parameters: - * N how many bits per iteration we try to get (4) - * WORDSIZE total number of bits (32) - * - * Derived constants: - * TOPBITS number of bits in the top `decade' of a number - * - * Important variables: - * Q the partial quotient under development (initially 0) - * R the remainder so far, initially the dividend - * ITER number of main division loop iterations required; - * equal to ceil(log2(quotient) / N). Note that this - * is the log base (2^N) of the quotient. - * V the current comparand, initially divisor*2^(ITER*N-1) - * - * Cost: - * Current estimate for non-large dividend is - * ceil(log2(quotient) / N) * (10 + 7N/2) + C - * A large dividend is one greater than 2^(31-TOPBITS) and takes a - * different path, as the upper bits of the quotient must be developed - * one bit at a time. - */ - -define(N, `4')dnl -define(WORDSIZE, `32')dnl -define(TOPBITS, eval(WORDSIZE - N*((WORDSIZE-1)/N)))dnl -dnl -define(dividend, `%o0')dnl -define(divisor, `%o1')dnl -define(Q, `%o2')dnl -define(R, `%o3')dnl -define(ITER, `%o4')dnl -define(V, `%o5')dnl -dnl -dnl m4 reminder: ifelse(a,b,c,d) => if a is b, then c, else d -define(T, `%g1')dnl -define(SC, `%g2')dnl -ifelse(S, `true', `define(SIGN, `%g3')')dnl - -dnl -dnl This is the recursive definition for developing quotient digits. -dnl -dnl Parameters: -dnl $1 the current depth, 1 <= $1 <= N -dnl $2 the current accumulation of quotient bits -dnl N max depth -dnl -dnl We add a new bit to $2 and either recurse or insert the bits in -dnl the quotient. R, Q, and V are inputs and outputs as defined above; -dnl the condition codes are expected to reflect the input R, and are -dnl modified to reflect the output R. -dnl -define(DEVELOP_QUOTIENT_BITS, -` ! depth $1, accumulated bits $2 - bl LOC($1.eval(2**N+$2)) - srl V,1,V - ! remainder is positive - subcc R,V,R - ifelse($1, N, - ` b 9f - add Q, ($2*2+1), Q -', ` DEVELOP_QUOTIENT_BITS(incr($1), `eval(2*$2+1)')') -LOC($1.eval(2**N+$2)): - ! remainder is negative - addcc R,V,R - ifelse($1, N, - ` b 9f - add Q, ($2*2-1), Q -', ` DEVELOP_QUOTIENT_BITS(incr($1), `eval(2*$2-1)')') -ifelse($1, 1, `9:')')dnl - -#include <sysdep.h> -#include <sys/trap.h> - -ENTRY(NAME) -ifelse(S, `true', -` ! compute sign of result; if neither is negative, no problem - orcc divisor, dividend, %g0 ! either negative? - bge 2f ! no, go do the divide -ifelse(OP, `div', -` xor divisor, dividend, SIGN ! compute sign in any case', -` mov dividend, SIGN ! sign of remainder matches dividend') - tst divisor - bge 1f - tst dividend - ! divisor is definitely negative; dividend might also be negative - bge 2f ! if dividend not negative... - sub %g0, divisor, divisor ! in any case, make divisor nonneg -1: ! dividend is negative, divisor is nonnegative - sub %g0, dividend, dividend ! make dividend nonnegative -2: -') - ! Ready to divide. Compute size of quotient; scale comparand. - orcc divisor, %g0, V - bne 1f - mov dividend, R - - ! Divide by zero trap. If it returns, return 0 (about as - ! wrong as possible, but that is what SunOS does...). - ta ST_DIV0 - retl - clr %o0 - -1: - cmp R, V ! if divisor exceeds dividend, done - blu LOC(got_result) ! (and algorithm fails otherwise) - clr Q - sethi %hi(1 << (WORDSIZE - TOPBITS - 1)), T - cmp R, T - blu LOC(not_really_big) - clr ITER - - ! `Here the dividend is >= 2**(31-N) or so. We must be careful here, - ! as our usual N-at-a-shot divide step will cause overflow and havoc. - ! The number of bits in the result here is N*ITER+SC, where SC <= N. - ! Compute ITER in an unorthodox manner: know we need to shift V into - ! the top decade: so do not even bother to compare to R.' - 1: - cmp V, T - bgeu 3f - mov 1, SC - sll V, N, V - b 1b - add ITER, 1, ITER - - ! Now compute SC. - 2: addcc V, V, V - bcc LOC(not_too_big) - add SC, 1, SC - - ! We get here if the divisor overflowed while shifting. - ! This means that R has the high-order bit set. - ! Restore V and subtract from R. - sll T, TOPBITS, T ! high order bit - srl V, 1, V ! rest of V - add V, T, V - b LOC(do_single_div) - sub SC, 1, SC - - LOC(not_too_big): - 3: cmp V, R - blu 2b - nop - be LOC(do_single_div) - nop - /* NB: these are commented out in the V8-Sparc manual as well */ - /* (I do not understand this) */ - ! V > R: went too far: back up 1 step - ! srl V, 1, V - ! dec SC - ! do single-bit divide steps - ! - ! We have to be careful here. We know that R >= V, so we can do the - ! first divide step without thinking. BUT, the others are conditional, - ! and are only done if R >= 0. Because both R and V may have the high- - ! order bit set in the first step, just falling into the regular - ! division loop will mess up the first time around. - ! So we unroll slightly... - LOC(do_single_div): - subcc SC, 1, SC - bl LOC(end_regular_divide) - nop - sub R, V, R - mov 1, Q - b LOC(end_single_divloop) - nop - LOC(single_divloop): - sll Q, 1, Q - bl 1f - srl V, 1, V - ! R >= 0 - sub R, V, R - b 2f - add Q, 1, Q - 1: ! R < 0 - add R, V, R - sub Q, 1, Q - 2: - LOC(end_single_divloop): - subcc SC, 1, SC - bge LOC(single_divloop) - tst R - b,a LOC(end_regular_divide) - -LOC(not_really_big): -1: - sll V, N, V - cmp V, R - bleu 1b - addcc ITER, 1, ITER - be LOC(got_result) - sub ITER, 1, ITER - - tst R ! set up for initial iteration -LOC(divloop): - sll Q, N, Q - DEVELOP_QUOTIENT_BITS(1, 0) -LOC(end_regular_divide): - subcc ITER, 1, ITER - bge LOC(divloop) - tst R - bl,a LOC(got_result) - ! non-restoring fixup here (one instruction only!) -ifelse(OP, `div', -` sub Q, 1, Q -', ` add R, divisor, R -') - -LOC(got_result): -ifelse(S, `true', -` ! check to see if answer should be < 0 - tst SIGN - bl,a 1f - ifelse(OP, `div', `sub %g0, Q, Q', `sub %g0, R, R') -1:') - retl - ifelse(OP, `div', `mov Q, %o0', `mov R, %o0') - -END(NAME) -ifelse(OP, `div', ifelse(S, `false', `strong_alias (.udiv, __wrap_.udiv) -'))dnl |