* config/h8300/lib1funcs.asm (DenHighNonZero): Optimize using

	the approximate quotient method.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@73550 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0199852..4bf3f91 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2003-11-13  Pavel Pisa  <pisa@cmp.felk.cvut.cz>
+           Kazu Hirata  <kazu@cs.umass.edu>
+
+       * config/h8300/lib1funcs.asm (DenHighNonZero): Optimize using
+       the approximate quotient method.
+
 2003-11-13  Richard Earnshaw  <rearnsha@arm.com>
 
        * combine.c (distribute_notes): When re-distributing the notes from

diff --git a/gcc/config/h8300/lib1funcs.asm b/gcc/config/h8300/lib1funcs.asm
index 7ef956f..d71a11e 100644 (file)
--- a/gcc/config/h8300/lib1funcs.asm
+++ b/gcc/config/h8300/lib1funcs.asm
@@ -603,32 +603,57 @@ divmodsi4:
        extu.l  S0P
        rts
 
+       ; er0 = er0 / er1
+       ; er4 = er0 % er1
+       ; trashes er1 er2
+       ; expects er1 >= 2^16
 DenHighNonZero:
-       sub.l   S0P,S0P         ; zero play area
-       mov.w   A0E,A2
-       mov.b   A2H,S0L
-       mov.b   A2L,A2H
-       mov.b   A0H,A2L
-       mov.w   A2,A0E
-       mov.b   A0L,A0H
-       mov.b   #0,A0L
-       mov.b   #24,S2H         ; only do 24 iterations
-
-nextbit:
-       shll.l  A0P             ; double the answer guess
-       rotxl.l S0P             ; double remainder
-       sub.l   A1P,S0P         ; does it all fit?
-       bhs     setone
-
-       add.l   A1P,S0P         ; no, restore mistake
-       dec     S2H
-       bne     nextbit
-       rts
-
-setone:
-       inc     A0L
-       dec     S2H
-       bne     nextbit
+       mov.l   er0,er4
+       mov.l   er1,er2
+#ifdef __H8300H__
+divmod_L21:
+       shlr.l  er0
+       shlr.l  er2             ; make divisor < 2^16
+       mov.w   e2,e2
+       bne     divmod_L21
+#else
+       bra     divmod_L22
+divmod_L21:
+       shlr.l  #2,er0
+divmod_L22:
+       shlr.l  #2,er2          ; make divisor < 2^16
+       mov.w   e2,e2
+       bne     divmod_L21
+       rotxl.w r2
+       bcs     divmod_L23
+       shlr.l  er0
+       bra     divmod_L24
+divmod_L23:
+       rotxr.w r2
+       shlr.l  #2,er0
+divmod_L24:
+#endif
+       ;; At this point,
+       ;;  er0 contains shifted dividend
+       ;;  er1 contains divisor
+       ;;  er2 contains shifted divisor
+       ;;  er4 contains dividend, later remainder
+       divxu.w r2,er0          ; e0 now contains the approximate quotient (AQ)
+       extu.l  er0
+       beq     divmod_L25
+       subs    #1,er0          ; er0 = AQ - 1
+       mov.w   e1,r2
+       mulxu.w r0,er2          ; er2 = upper (AQ - 1) * divisor
+       sub.w   r2,e4           ; dividend - 65536 * er2
+       mov.w   r1,r2
+       mulxu.w r0,er2          ; compute er4 = remainder (tentative)
+       sub.l   er2,er4         ; er4 = dividend - (AQ - 1) * divisor
+divmod_L25:
+       cmp.l   er1,er4         ; is divisor < remainder?
+       blo     divmod_L26
+       adds    #1,er0
+       sub.l   er1,er4         ; correct the remainder
+divmod_L26:
        rts
 
 #endif