From f2a6af0995512835bae7e6ecd094e15ef5115fc3 Mon Sep 17 00:00:00 2001 From: Brooke Vibber Date: Thu, 3 Jul 2025 18:43:10 -0700 Subject: [PATCH] Replace the not-enough-precision 32 bit to float impl keep the proc though to encapsulate it but uses the older logic of rounding down to 3.13 first --- mandel.s | 79 +++----------------------------------------------------- 1 file changed, 4 insertions(+), 75 deletions(-) diff --git a/mandel.s b/mandel.s index 4cc0f39..a97d6e3 100644 --- a/mandel.s +++ b/mandel.s @@ -261,28 +261,6 @@ fixed3_13_as_float: ; float48 .byte $00 .byte $00 -u65536_as_float: ; float48 - ; 1 << 16 - ; 65536 - ; 06 55 36 . 00 00 - .byte 66 ; exponent/sign - +2 bytes - .byte $06 - .byte $55 - .byte $36 - .byte $00 - .byte $00 - -fixed6_26_as_float: ; float48 - ; 1 << 26 - ; 67108864 - ; 67 10 88 64 . 00 - .byte 67 ; exponent/sign - +3 bytes - .byte $67 - .byte $10 - .byte $88 - .byte $64 - .byte $00 - sec_per_frame: ; float48 00 . 01 66 66 66 67 .byte 63 ; exponent/sign - -1 bytes .byte $01 ; BCD digits @@ -1016,63 +994,14 @@ common: .endproc +; rounds to 16-bit first! ; input in FR0, 32 bits signed 6.26 fixed ; output in FR0, Atari float ; clobbers a, x, y, FR0, FR1 .proc fixed6_26_to_float - ; check sign bit! conversion routine is for unsigned - lda FR0 + 3 - and #$80 - sta temp - - beq positive - neg32 FR0 -positive: - - ; save low word - lda FR0 - pha - lda FR0 + 1 - pha - - ; convert high word - sta FR0 + 2 - sta FR1 - lda FR0 + 3 - sta FR0 + 1 - jsr IFP - - lda temp - beq positive2 - ; set float sign bit - lda FR0 - ora #$80 - sta FR0 -positive2: - - ; high word to FR1 - ldx #.lobyte(u65536_as_float) - ldy #.hibyte(u65536_as_float) - jsr FLD1R - jsr FMUL - jsr FMOVE - - ; convert low word - pla - lda temp + 1 - pla - lda temp - jsr IFP - - ; combine - jsr FADD - - ; scale - ldx #.lobyte(fixed6_26_as_float) - ldy #.hibyte(fixed6_26_as_float) - jsr FLD1R - jsr FDIV - + shift_round_16 FR0, 3 + copy16 FR0, FR0 + 2 + jsr fixed3_13_to_float rts .endproc