Reorg of exception handling code in the core blitter
* Moved V-flag handling outside of the 32-byte exception handler * Switched relative branches to JMP to save a cycle per word * Updated macros to create a full code snippet instead of assuming certain values exist in the exception handler buffer
This commit is contained in:
Lucas Scharenbroich
parent
0a9eb76ab5
commit
4c31a0d056
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@ -219,7 +219,7 @@ mixed cmp #$FFFF ; All 1's in the mask is fully transparent
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; This is the slowest path because there is a *lot* of work to do. So much that it's
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; worth it to change up the environment to optimize things a bit more.
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;
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; Need to fill in the first 8 bytes of the JMP handler with the following code sequence
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; Need to fill in the first 10 bytes of the JMP handler with the following code sequence
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;
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; lda (00),y
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; and #MASK
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@ -252,6 +252,9 @@ mixed cmp #$FFFF ; All 1's in the mask is fully transparent
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lda ]1
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sta: $0006,y
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lda #$0D80 ; branch to the prologue (BRA *+15)
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sta: $0008,y
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ldy _Y_REG ; restore original y-register value and move on
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bra next
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@ -321,6 +324,9 @@ mixed cmp #$FFFF ; All 1's in the mask is fully transparent
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ldal ]1,x
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sta: $0006,y
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lda #$0D80 ; branch to the prologue (BRA *+15)
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sta: $0008,y
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ldy _Y_REG ; restore original y-register value and move on
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bra next
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@ -346,12 +352,11 @@ next
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; ]3 : code field offset
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CopyMaskedDWord MAC
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; Need to fill in the first 8 bytes of the JMP handler with the following code sequence
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; Need to fill in the first 6 bytes of the JMP handler with the following code sequence
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;
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; lda (00),y
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; and $80,x
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; ora $00,x
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; bcc *+4
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ldx _X_REG ; Get the addressing offset
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ldal JTableOffset,x ; Get the address offset and add to the base address
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@ -377,7 +382,7 @@ CopyMaskedDWord MAC
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sta: $0004,x ; Set ORA 00,x opcode
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rep #$30
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lda #$0290 ; BCC *+4
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lda #$0F80 ; branch to the prologue (BRA *+17)
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sta: $0006,x
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eom
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@ -392,25 +397,17 @@ CopyMaskedDWord MAC
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; ]3 : code field offset
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CopyMaskedDynSpriteWord MAC
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; Need to fill in the first 12(!!) bytes of the JMP handler with the following code sequence
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; Need to fill in the first 12 bytes of the JMP handler with the following code sequence
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;
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; lda (00),y
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; and $80,x
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; ora $00,x
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; and #MASK
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; ora #DATA
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; bra *+11
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;
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; If MASK == 0, then we can do a PEA. If MASK == $FFFF, then fall back to the simple Dynamic Masked
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; code.
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;
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; If the tile priority bit is set, then we use an alternate bit of code that changes to oder
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; of operations to and can't make an assumption about the transparency
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;
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; lda (00),y
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; and #MASK
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; ora #DATA
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; and $80,x
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; ora $00,x
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ldx _X_REG ; Get the addressing offset
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@ -432,11 +429,21 @@ CopyMaskedDynSpriteWord MAC
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ora #$80
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sta: $0003,x ; Set AND 00,x operand
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lda #$35
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sta: $0002,x ; Set AND 00,x operand
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sta: $0002,x ; Set AND 00,x opcode
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lda #$15
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sta: $0004,x ; Set ORA 00,x operand
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rep #$30
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sta: $0004,x ; Set ORA 00,x opcode
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lda #$0290 ; BCC *+4
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sta: $0006,x
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lda #$29
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sta: $0006,y ; AND #$0000 opcode
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lda #$09
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sta: $0009,y ; ORA #$0000 opcode
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rep #$20
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lda ]1+32 ; insert the tile mask and data into the exception
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sta: $0007,y ; handler.
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lda ]1
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sta: $000A,y
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lda #$0990 ; BCC *+11
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sta: $000C,x
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eom
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@ -37,8 +37,18 @@ PagePatches da {long_0-base+2}
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da {loop_back-base+2}
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da {loop_exit_3-base+2}
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da {even_exit-base+2}
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da {jmp_rtn_1-base+2}
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da {jmp_rtn_2-base+2}
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]index equ 0
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lup 82 ; All the snippet addresses. The two JMP
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da {snippets-base+{]index*32}+31} ; instructino are at the end of each of
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da {snippets-base+{]index*32}+28} ; the 32-byte buffers
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]index equ ]index+1
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--^
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PagePatchNum equ *-PagePatches
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; Location that need a bank byte set for long addressing modes
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BankPatches da {long_0-base+3}
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da {long_1-base+3}
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da {long_2-base+3}
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@ -483,7 +493,9 @@ BuildBank
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; 13 banks for a total of 208 lines, which is what is required to render 26 tiles
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; to cover the full screen vertical scrolling.
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;
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; The 'base' location is always assumed to be on a 4kb ($1000) boundary
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; The 'base' location is always assumed to be on a 4kb ($1000) boundary. We make sure that
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; the code is assembled on a page boundary to help will alignment
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ds \,$00 ; pad to the next page boundary
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base
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entry_1 ldx #0000 ; Used for LDA 00,x addressing
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entry_2 ldy #0000 ; Used for LDA (00),y addressing
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@ -538,7 +550,7 @@ long_3 stal *+5-base
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full_return jml blt_return ; Full exit
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; Re-enable interrupts and continue -- the even_exit JMP from the previous line will jump here every
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; 8 or 16 lines in order to give the system some extra time to handle interrupts.
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; 8 or 16 lines in order to give the system time to handle interrupts.
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enable_int ldal stk_save+1 ; restore the stack
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tcs
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sep #$20 ; 8-bit mode
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@ -554,13 +566,26 @@ enable_int ldal stk_save+1 ; restore the stack
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rep #$20
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bra entry_1
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; The even/odd branch of this line's exception handler will return here. This is mostly
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; a space-saving measure to allow for more code in the exeption handers themselved, but
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; also simplified the relocation process since we only have to update a single address
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; in each exception handler, rather than two.
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;
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; Oce working, this code should be able to be interleaved with the r_jmp_rtn code
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; above to eliminate a couple of branches
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jmp_rtn
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bvs jmp_rtn_v ; overflow set means this is the right edge (entry)
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clc ; carry is set only for edge operations; force clear
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jmp_rtn_1 jmp l_jmp_rtn-base
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jmp_rtn_v rep #$41 ; clear V and C
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jmp_rtn_2 jmp r_jmp_rtn-base
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; This is the spot that needs to be page-aligned. In addition to simplifying the entry address
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; and only needing to update a byte instad of a word, because the code breaks out of the
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; code field with a BRA instruction, we keep everything within a page to avoid the 1-cycle
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; page-crossing penalty of the branch.
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ds 166
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ds \,$00 ; pad to the next page boundary
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loop_exit_1 jmp odd_exit-base ; +0 Alternate exit point depending on whether the left edge is
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loop_exit_2 jmp even_exit-base ; +3 odd-aligned
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@ -685,32 +710,25 @@ epilogue_1 tsc
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; r_edge rep #$41
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; brl r_jmp_rtn ; 3
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; Each snippet is provided 32 bytes of space. The constant code is filled in from the end and
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; it is the responsibility of the code that fills in the hander to create valid program in the
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; first 23 bytes are available to be manipulated.
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;
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; Note that the code that's assembled in the first bytes of these snippets is just an example. Every
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; routine that created an exception handler *MUST* write a full set of instructions since there is
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; no guarantee of what was written previously.
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ds \,$00 ; pad to the next page boundary
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]index equ 0
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snippets lup 82
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ds 2 ; space for a 2-byte sequence; LDA (00),y LDA 00,x LDA 0,s
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ds 2 ; space for all exception handlers
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and #$0000 ; the mask operand will be set when the tile is drawn
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ora #$0000 ; the data operand will be set when the tile is drawn
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bcs *+6
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pha
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brl loop+3+{3*]index} ; use relative branch for convenience
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bvs *+6 ; overflow set means this is the right edge (entry)
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clc ; carry is set only for edge operations; force clear
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brl l_jmp_rtn
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rep #$41 ; clear V and C
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brl r_jmp_rtn ; 25 bytes
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ds 7 ; padding
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ds 15 ; extra padding
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bcs :byte ; if C = 0, just push the data and return
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pha ; 1 byte
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jmp loop+3+{3*]index}-base ; 3 bytes : use relative branch for convenience
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:byte jmp jmp_rtn-base ; 3 bytes
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]index equ ]index+1
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--^
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top
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