From e284587edc743cce7961c61c0c0ccacce9ce9edd Mon Sep 17 00:00:00 2001 From: Brooke Vibber Date: Sat, 22 Aug 2026 15:35:03 -0700 Subject: [PATCH] Fix regression from merging ptr and pixel_ptr the XE fast-path assumed low byte of ptr never changes to save a couple cycles --- mandel-core.s | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/mandel-core.s b/mandel-core.s index 34dff8b..348e072 100644 --- a/mandel-core.s +++ b/mandel-core.s @@ -18,6 +18,7 @@ z_buffer_start: .res 1 ; u8: index into z_buffer z_buffer_end: .res 1 ; u8: index into z_buffer iter: .res 1 ; u8: iteration count ptr: .res 2 ; u16 +pixel_ptr: .res 2 ; u16 temp: .res 2 ; u16 temp2: .res 2 ; u16 @@ -1254,21 +1255,21 @@ enough: negative: ; temp1 = top half lda #.lobyte(framebuffer_top + stride * half_height) - sta ptr + sta pixel_ptr lda #.hibyte(framebuffer_top + stride * half_height) - sta ptr + 1 + sta pixel_ptr + 1 jmp point positive: lda #.lobyte(framebuffer_bottom) - sta ptr + sta pixel_ptr lda #.hibyte(framebuffer_bottom) - sta ptr + 1 + sta pixel_ptr + 1 point: - ; ptr += sy * stride + ; pixel_ptr += sy * stride ; temp * 40 ; = temp * 32 + temp * 8 ; = (temp << 5) + (temp << 3) @@ -1276,10 +1277,10 @@ point: shl16 temp shl16 temp shl16 temp - add16 ptr, ptr, temp + add16 pixel_ptr, pixel_ptr, temp shl16 temp shl16 temp - add16 ptr, ptr, temp + add16 pixel_ptr, pixel_ptr, temp ; Ok so temp1 points to the start of the line, which is 40 bytes. ; Get the byte and bit offsets @@ -1319,20 +1320,20 @@ shift_done: draw_pixel: ; read, mask, or, write - lda (ptr),y + lda (pixel_ptr),y and pixel_mask ora pixel_color - sta (ptr),y + sta (pixel_ptr),y dex beq done clc lda #40 - adc ptr - sta ptr + adc pixel_ptr + sta pixel_ptr lda #0 - adc ptr + 1 - sta ptr + 1 + adc pixel_ptr + 1 + sta pixel_ptr + 1 jmp draw_pixel done: