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Diffstat (limited to 'c/src/lib/libcpu/m68k/m68040/fpsp/srem_mod.S')
| -rw-r--r-- | c/src/lib/libcpu/m68k/m68040/fpsp/srem_mod.S | 424 |
1 files changed, 424 insertions, 0 deletions
diff --git a/c/src/lib/libcpu/m68k/m68040/fpsp/srem_mod.S b/c/src/lib/libcpu/m68k/m68040/fpsp/srem_mod.S new file mode 100644 index 0000000000..8bbcb8a3de --- /dev/null +++ b/c/src/lib/libcpu/m68k/m68040/fpsp/srem_mod.S @@ -0,0 +1,424 @@ +// +// $Id$ +// +// srem_mod.sa 3.1 12/10/90 +// +// The entry point sMOD computes the floating point MOD of the +// input values X and Y. The entry point sREM computes the floating +// point (IEEE) REM of the input values X and Y. +// +// INPUT +// ----- +// Double-extended value Y is pointed to by address in register +// A0. Double-extended value X is located in -12(A0). The values +// of X and Y are both nonzero and finite; although either or both +// of them can be denormalized. The special cases of zeros, NaNs, +// and infinities are handled elsewhere. +// +// OUTPUT +// ------ +// FREM(X,Y) or FMOD(X,Y), depending on entry point. +// +// ALGORITHM +// --------- +// +// Step 1. Save and strip signs of X and Y: signX := sign(X), +// signY := sign(Y), X := |X|, Y := |Y|, +// signQ := signX EOR signY. Record whether MOD or REM +// is requested. +// +// Step 2. Set L := expo(X)-expo(Y), k := 0, Q := 0. +// If (L < 0) then +// R := X, go to Step 4. +// else +// R := 2^(-L)X, j := L. +// endif +// +// Step 3. Perform MOD(X,Y) +// 3.1 If R = Y, go to Step 9. +// 3.2 If R > Y, then { R := R - Y, Q := Q + 1} +// 3.3 If j = 0, go to Step 4. +// 3.4 k := k + 1, j := j - 1, Q := 2Q, R := 2R. Go to +// Step 3.1. +// +// Step 4. At this point, R = X - QY = MOD(X,Y). Set +// Last_Subtract := false (used in Step 7 below). If +// MOD is requested, go to Step 6. +// +// Step 5. R = MOD(X,Y), but REM(X,Y) is requested. +// 5.1 If R < Y/2, then R = MOD(X,Y) = REM(X,Y). Go to +// Step 6. +// 5.2 If R > Y/2, then { set Last_Subtract := true, +// Q := Q + 1, Y := signY*Y }. Go to Step 6. +// 5.3 This is the tricky case of R = Y/2. If Q is odd, +// then { Q := Q + 1, signX := -signX }. +// +// Step 6. R := signX*R. +// +// Step 7. If Last_Subtract = true, R := R - Y. +// +// Step 8. Return signQ, last 7 bits of Q, and R as required. +// +// Step 9. At this point, R = 2^(-j)*X - Q Y = Y. Thus, +// X = 2^(j)*(Q+1)Y. set Q := 2^(j)*(Q+1), +// R := 0. Return signQ, last 7 bits of Q, and R. +// +// + +// Copyright (C) Motorola, Inc. 1990 +// All Rights Reserved +// +// THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA +// The copyright notice above does not evidence any +// actual or intended publication of such source code. + +SREM_MOD: //idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + +#include "fpsp.defs" + + .set Mod_Flag,L_SCR3 + .set SignY,FP_SCR3+4 + .set SignX,FP_SCR3+8 + .set SignQ,FP_SCR3+12 + .set Sc_Flag,FP_SCR4 + + .set Y,FP_SCR1 + .set Y_Hi,Y+4 + .set Y_Lo,Y+8 + + .set R,FP_SCR2 + .set R_Hi,R+4 + .set R_Lo,R+8 + + +Scale: .long 0x00010000,0x80000000,0x00000000,0x00000000 + + |xref t_avoid_unsupp + + .global smod +smod: + + movel #0,Mod_Flag(%a6) + bras Mod_Rem + + .global srem +srem: + + movel #1,Mod_Flag(%a6) + +Mod_Rem: +//..Save sign of X and Y + moveml %d2-%d7,-(%a7) // ...save data registers + movew (%a0),%d3 + movew %d3,SignY(%a6) + andil #0x00007FFF,%d3 // ...Y := |Y| + +// + movel 4(%a0),%d4 + movel 8(%a0),%d5 // ...(D3,D4,D5) is |Y| + + tstl %d3 + bnes Y_Normal + + movel #0x00003FFE,%d3 // ...$3FFD + 1 + tstl %d4 + bnes HiY_not0 + +HiY_0: + movel %d5,%d4 + clrl %d5 + subil #32,%d3 + clrl %d6 + bfffo %d4{#0:#32},%d6 + lsll %d6,%d4 + subl %d6,%d3 // ...(D3,D4,D5) is normalized +// ...with bias $7FFD + bras Chk_X + +HiY_not0: + clrl %d6 + bfffo %d4{#0:#32},%d6 + subl %d6,%d3 + lsll %d6,%d4 + movel %d5,%d7 // ...a copy of D5 + lsll %d6,%d5 + negl %d6 + addil #32,%d6 + lsrl %d6,%d7 + orl %d7,%d4 // ...(D3,D4,D5) normalized +// ...with bias $7FFD + bras Chk_X + +Y_Normal: + addil #0x00003FFE,%d3 // ...(D3,D4,D5) normalized +// ...with bias $7FFD + +Chk_X: + movew -12(%a0),%d0 + movew %d0,SignX(%a6) + movew SignY(%a6),%d1 + eorl %d0,%d1 + andil #0x00008000,%d1 + movew %d1,SignQ(%a6) // ...sign(Q) obtained + andil #0x00007FFF,%d0 + movel -8(%a0),%d1 + movel -4(%a0),%d2 // ...(D0,D1,D2) is |X| + tstl %d0 + bnes X_Normal + movel #0x00003FFE,%d0 + tstl %d1 + bnes HiX_not0 + +HiX_0: + movel %d2,%d1 + clrl %d2 + subil #32,%d0 + clrl %d6 + bfffo %d1{#0:#32},%d6 + lsll %d6,%d1 + subl %d6,%d0 // ...(D0,D1,D2) is normalized +// ...with bias $7FFD + bras Init + +HiX_not0: + clrl %d6 + bfffo %d1{#0:#32},%d6 + subl %d6,%d0 + lsll %d6,%d1 + movel %d2,%d7 // ...a copy of D2 + lsll %d6,%d2 + negl %d6 + addil #32,%d6 + lsrl %d6,%d7 + orl %d7,%d1 // ...(D0,D1,D2) normalized +// ...with bias $7FFD + bras Init + +X_Normal: + addil #0x00003FFE,%d0 // ...(D0,D1,D2) normalized +// ...with bias $7FFD + +Init: +// + movel %d3,L_SCR1(%a6) // ...save biased expo(Y) + movel %d0,L_SCR2(%a6) //save d0 + subl %d3,%d0 // ...L := expo(X)-expo(Y) +// Move.L D0,L ...D0 is j + clrl %d6 // ...D6 := carry <- 0 + clrl %d3 // ...D3 is Q + moveal #0,%a1 // ...A1 is k; j+k=L, Q=0 + +//..(Carry,D1,D2) is R + tstl %d0 + bges Mod_Loop + +//..expo(X) < expo(Y). Thus X = mod(X,Y) +// + movel L_SCR2(%a6),%d0 //restore d0 + bra Get_Mod + +//..At this point R = 2^(-L)X; Q = 0; k = 0; and k+j = L + + +Mod_Loop: + tstl %d6 // ...test carry bit + bgts R_GT_Y + +//..At this point carry = 0, R = (D1,D2), Y = (D4,D5) + cmpl %d4,%d1 // ...compare hi(R) and hi(Y) + bnes R_NE_Y + cmpl %d5,%d2 // ...compare lo(R) and lo(Y) + bnes R_NE_Y + +//..At this point, R = Y + bra Rem_is_0 + +R_NE_Y: +//..use the borrow of the previous compare + bcss R_LT_Y // ...borrow is set iff R < Y + +R_GT_Y: +//..If Carry is set, then Y < (Carry,D1,D2) < 2Y. Otherwise, Carry = 0 +//..and Y < (D1,D2) < 2Y. Either way, perform R - Y + subl %d5,%d2 // ...lo(R) - lo(Y) + subxl %d4,%d1 // ...hi(R) - hi(Y) + clrl %d6 // ...clear carry + addql #1,%d3 // ...Q := Q + 1 + +R_LT_Y: +//..At this point, Carry=0, R < Y. R = 2^(k-L)X - QY; k+j = L; j >= 0. + tstl %d0 // ...see if j = 0. + beqs PostLoop + + addl %d3,%d3 // ...Q := 2Q + addl %d2,%d2 // ...lo(R) = 2lo(R) + roxll #1,%d1 // ...hi(R) = 2hi(R) + carry + scs %d6 // ...set Carry if 2(R) overflows + addql #1,%a1 // ...k := k+1 + subql #1,%d0 // ...j := j - 1 +//..At this point, R=(Carry,D1,D2) = 2^(k-L)X - QY, j+k=L, j >= 0, R < 2Y. + + bras Mod_Loop + +PostLoop: +//..k = L, j = 0, Carry = 0, R = (D1,D2) = X - QY, R < Y. + +//..normalize R. + movel L_SCR1(%a6),%d0 // ...new biased expo of R + tstl %d1 + bnes HiR_not0 + +HiR_0: + movel %d2,%d1 + clrl %d2 + subil #32,%d0 + clrl %d6 + bfffo %d1{#0:#32},%d6 + lsll %d6,%d1 + subl %d6,%d0 // ...(D0,D1,D2) is normalized +// ...with bias $7FFD + bras Get_Mod + +HiR_not0: + clrl %d6 + bfffo %d1{#0:#32},%d6 + bmis Get_Mod // ...already normalized + subl %d6,%d0 + lsll %d6,%d1 + movel %d2,%d7 // ...a copy of D2 + lsll %d6,%d2 + negl %d6 + addil #32,%d6 + lsrl %d6,%d7 + orl %d7,%d1 // ...(D0,D1,D2) normalized + +// +Get_Mod: + cmpil #0x000041FE,%d0 + bges No_Scale +Do_Scale: + movew %d0,R(%a6) + clrw R+2(%a6) + movel %d1,R_Hi(%a6) + movel %d2,R_Lo(%a6) + movel L_SCR1(%a6),%d6 + movew %d6,Y(%a6) + clrw Y+2(%a6) + movel %d4,Y_Hi(%a6) + movel %d5,Y_Lo(%a6) + fmovex R(%a6),%fp0 // ...no exception + movel #1,Sc_Flag(%a6) + bras ModOrRem +No_Scale: + movel %d1,R_Hi(%a6) + movel %d2,R_Lo(%a6) + subil #0x3FFE,%d0 + movew %d0,R(%a6) + clrw R+2(%a6) + movel L_SCR1(%a6),%d6 + subil #0x3FFE,%d6 + movel %d6,L_SCR1(%a6) + fmovex R(%a6),%fp0 + movew %d6,Y(%a6) + movel %d4,Y_Hi(%a6) + movel %d5,Y_Lo(%a6) + movel #0,Sc_Flag(%a6) + +// + + +ModOrRem: + movel Mod_Flag(%a6),%d6 + beqs Fix_Sign + + movel L_SCR1(%a6),%d6 // ...new biased expo(Y) + subql #1,%d6 // ...biased expo(Y/2) + cmpl %d6,%d0 + blts Fix_Sign + bgts Last_Sub + + cmpl %d4,%d1 + bnes Not_EQ + cmpl %d5,%d2 + bnes Not_EQ + bra Tie_Case + +Not_EQ: + bcss Fix_Sign + +Last_Sub: +// + fsubx Y(%a6),%fp0 // ...no exceptions + addql #1,%d3 // ...Q := Q + 1 + +// + +Fix_Sign: +//..Get sign of X + movew SignX(%a6),%d6 + bges Get_Q + fnegx %fp0 + +//..Get Q +// +Get_Q: + clrl %d6 + movew SignQ(%a6),%d6 // ...D6 is sign(Q) + movel #8,%d7 + lsrl %d7,%d6 + andil #0x0000007F,%d3 // ...7 bits of Q + orl %d6,%d3 // ...sign and bits of Q + swap %d3 + fmovel %fpsr,%d6 + andil #0xFF00FFFF,%d6 + orl %d3,%d6 + fmovel %d6,%fpsr // ...put Q in fpsr + +// +Restore: + moveml (%a7)+,%d2-%d7 + fmovel USER_FPCR(%a6),%fpcr + movel Sc_Flag(%a6),%d0 + beqs Finish + fmulx Scale(%pc),%fp0 // ...may cause underflow + bra t_avoid_unsupp //check for denorm as a +// ;result of the scaling + +Finish: + fmovex %fp0,%fp0 //capture exceptions & round + rts + +Rem_is_0: +//..R = 2^(-j)X - Q Y = Y, thus R = 0 and quotient = 2^j (Q+1) + addql #1,%d3 + cmpil #8,%d0 // ...D0 is j + bges Q_Big + + lsll %d0,%d3 + bras Set_R_0 + +Q_Big: + clrl %d3 + +Set_R_0: + fmoves #0x00000000,%fp0 + movel #0,Sc_Flag(%a6) + bra Fix_Sign + +Tie_Case: +//..Check parity of Q + movel %d3,%d6 + andil #0x00000001,%d6 + tstl %d6 + beq Fix_Sign // ...Q is even + +//..Q is odd, Q := Q + 1, signX := -signX + addql #1,%d3 + movew SignX(%a6),%d6 + eoril #0x00008000,%d6 + movew %d6,SignX(%a6) + bra Fix_Sign + + //end |