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[/] [forwardcom/] [libraries/] [print_integer_light.as] - Blame information for rev 118

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1 98 Agner
/***************************  print_integer_light.as **************************
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* Author:        Agner Fog
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* date created:  2021-05-16
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* Last modified: 2021-05-16
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* Version:       1.11
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* Project:       ForwardCom library libc_light.li
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* Description:   puts: print a string to stdout. Does not append linefeed
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* This version is for CPUs with limited capabilities
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* C declaration: void print_integer(int32_t i);
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* C declaration: void print_unsigned(uint32_t i);
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*
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* Copyright 2021 GNU General Public License http://www.gnu.org/licenses
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******************************************************************************/
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code section execute align = 4                   // code section
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// Print a 32-bit signed integer as decimal number to stdout
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_print_integer function public reguse=3,0
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if (int32 r0 < 0) {
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    int32 r0 = -r0
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    int8+ r1 = '-'
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    int8 output(r1, r1, 10)  // print '-'
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}
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// continue in _print_unsigned
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// Print a 32-bit unsigned integer as decimal number to stdout
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_print_unsigned function public reguse=3,0
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// This function is using the double dabble algorithm for binary to BCD conversion.
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// This method is slow, but it is used here because it does not require division
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// or multiplication. This makes sure it will work on small cores without mul and div instructions.
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// save r2-r5
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int64 sp -= 4*8
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int64 [sp]      = r2
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int64 [sp+8]    = r3
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int64 [sp+0x10] = r4
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int64 [sp+0x18] = r5
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// First two BCD digits are made with simple subtraction to avoid the need for a larger bit field
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int r5 = 0
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while (uint32 r0 >= 1000000000) {
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    uint32 r0 -= 1000000000
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    uint32 r5 += 0x10
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}
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while (uint32 r0 >= 100000000) {
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    uint32 r0 -= 100000000
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    uint32 r5 += 0x01
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}
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uint32 r5 <<= 24
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// Generate 8 BCD digits using double dabble algorithm
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int32 r1 = 0
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for (int r2 = 0; r2 < 32; r2++) {           // loop for 32 bits
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    int32 r3 = r1 + 0x33333333              // digit values 5-9 will set bit 3 in each 4-bit nibble
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    int32 r3 &= 0x88888888                  // isolate bit 3 in each nibble
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    int32 r4 = r3 >> 3                      // generate value 3 in nibbles with value 5-9
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    int32 r3 >>= 2
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    int32 r3 |= r4                          // this will have 3 for each nibble with a value 5-9
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    int32 r1 += r3                          // add 3 to nibble values 5-9 to generate 8-12
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    int32 r1 = funnel_shift(r0, r1, 31)     // shift most significant bit of r0 into r1
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    int32 r0 <<= 1
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}
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// r5:r1 = BCD value
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int r4 = 0                                  // remember if first digit has been printed
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for (int r2 = 2; r2 > 0; r2--) {
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    int32 r5 = rotate(r5, 4)                // get most significant digit first
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    int8 r3 = r5 & 0x0F
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    int r4 = (r3 != 0) || r4                // digit has been printed
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    int8 r3 += '0'
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    if (int r4 != 0) {
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        int8 output(r3, r3, 10)             // print character to stdout
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    }
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}
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// print 8 decimal digits
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for (int r2 = 8; r2 > 0; r2--) {
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    int32 r1 = rotate(r1, 4)                // get most significant digit first
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    int8 r3 = r1 & 0x0F
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    int r4 = (r3 != 0) || r4                // digit has been printed
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    int r4 = (r2 == 1) || r4                // last digit must be printed
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    int8 r3 += '0'
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    if (int r4 != 0) {
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        int8 output(r3, r3, 10)             // print character to stdout
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    }
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}
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// restore r2-r5
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int64 r2 = [sp]
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int64 r3 = [sp+8]
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int64 r4 = [sp+0x10]
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int64 r5 = [sp+0x18]
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int64 sp += 4*8
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return
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_print_integer end
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code end

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