passing destoer isr test, booting kirby, failing tonc irq_demo

- handle exception returns after alu
- proper spsr banking
- fill pipeline before interrupts
- align r15 before each pipeline fill

src/crab/arm/data_processing.cr

@@ -16,12 +16,6 @@ module ARM
                 else # Operand 2 is a register
                   rotate_register bits(instr, 0..11), pointerof(barrel_shifter_carry_out)
                 end
-    if rd == 15 && set_conditions
-      old_spsr = @spsr.value
-      switch_mode CPU::Mode.from_value @spsr.mode
-      @cpsr.value = old_spsr
-      set_conditions = false
-    end
     case opcode
     when 0b0000 # AND
       set_reg(rd, @r[rn] & operand_2)
@@ -84,5 +78,12 @@ module ARM
     else raise "Unimplemented execution of data processing opcode: #{hex_str opcode}"
     end
     @r[15] &-= 4 if pc_reads_12_ahead
+    if rd == 15 && set_conditions
+      old_spsr = @spsr.value
+      new_mode = CPU::Mode.from_value(@spsr.mode)
+      switch_mode new_mode
+      @cpsr.value = old_spsr
+      @spsr.value = new_mode.bank == 0 ? @cpsr.value : @spsr_banks[new_mode.bank]
+    end
   end
 end

src/crab/arm/psr_transfer.cr

@@ -1,21 +1,28 @@
 module ARM
   def arm_psr_transfer(instr : Word) : Nil
     spsr = bit?(instr, 22)
+    mode = CPU::Mode.from_value @cpsr.mode
+    has_spsr = mode != CPU::Mode::USR && mode != CPU::Mode::SYS
+
     if bit?(instr, 21) # MSR
-      mask = 0_u32 # described in gbatek, not in arm manual https://problemkaputt.de/gbatek.htm#armopcodespsrtransfermrsmsr
+      mask = 0_u32
       mask |= 0xFF000000 if bit?(instr, 19) # f (aka _flg)
       mask |= 0x00FF0000 if bit?(instr, 18) # s
       mask |= 0x0000FF00 if bit?(instr, 17) # x
       mask |= 0x000000FF if bit?(instr, 16) # c (aka _ctl)
-      if bit?(instr, 25) # immediate
+
+      if bit?(instr, 25)                 # immediate
         barrel_shifter_carry_out = false # unused, doesn't matter
         value = immediate_offset bits(instr, 0..11), pointerof(barrel_shifter_carry_out)
       else # register value
         value = @r[bits(instr, 0..3)]
       end
+
       value &= mask
       if spsr
-        @spsr.value = (@spsr.value & ~mask) | value
+        if has_spsr
+          @spsr.value = (@spsr.value & ~mask) | value
+        end
       else
         thumb = @cpsr.thumb
         switch_mode CPU::Mode.from_value value & 0x1F if mask & 0xFF > 0
@@ -24,7 +31,7 @@ module ARM
       end
     else # MRS
       rd = bits(instr, 12..15)
-      if spsr
+      if spsr && has_spsr
         set_reg(rd, @spsr.value)
       else
         set_reg(rd, @cpsr.value)

src/crab/cpu.cr

@@ -40,12 +40,13 @@ class CPU
   end
 
   getter r = Slice(Word).new 16
-  @cpsr : PSR = PSR.new 0x0000001F
-  @spsr : PSR = PSR.new 0
+  @cpsr : PSR = PSR.new CPU::Mode::SYS.value
+  @spsr : PSR = PSR.new CPU::Mode::SYS.value
   getter pipeline = Pipeline.new
   getter lut : Slice(Proc(Word, Nil)) { fill_lut }
   getter thumb_lut : Slice(Proc(Word, Nil)) { fill_thumb_lut }
-  @reg_banks = Array(Array(Word)).new 6 { Array(Word).new 8, 0 }
+  @reg_banks = Array(Array(Word)).new 6 { Array(Word).new 7, 0 }
+  @spsr_banks = Array(Word).new 6, CPU::Mode::SYS.value # logically independent of typical register banks
 
   def initialize(@gba : GBA)
     @reg_banks[Mode::USR.bank][5] = @r[13] = 0x03007F00
@@ -57,8 +58,6 @@ class CPU
   def switch_mode(new_mode : Mode) : Nil
     old_mode = Mode.from_value @cpsr.mode
     return if new_mode == old_mode
-    @spsr.value = @cpsr.value
-    @cpsr.mode = new_mode.value
     new_bank = new_mode.bank
     old_bank = old_mode.bank
     if new_mode == Mode::FIQ || old_mode == Mode::FIQ
@@ -70,17 +69,20 @@ class CPU
     # store old regs
     @reg_banks[old_bank][5] = @r[13]
     @reg_banks[old_bank][6] = @r[14]
+    @spsr_banks[old_bank] = @spsr.value
     # load new regs
     @r[13] = @reg_banks[new_bank][5]
     @r[14] = @reg_banks[new_bank][6]
+    @spsr.value = @cpsr.value
+    @cpsr.mode = new_mode.value
   end
 
   def irq : Nil
     unless @cpsr.irq_disable
+      fill_pipeline
       lr = @r[15] - (@cpsr.thumb ? 0 : 4)
       switch_mode CPU::Mode::IRQ
       @cpsr.thumb = false
-      clear_pipeline
       @cpsr.irq_disable = true
       set_reg(14, lr)
       set_reg(15, 0x18)
@@ -88,6 +90,11 @@ class CPU
   end
 
   def fill_pipeline : Nil
+    if @cpsr.thumb # moved alignment to interpreter loop to fix exception returning
+      @r[15] &= ~1
+    else
+      @r[15] &= ~3
+    end
     while @pipeline.size < 2
       if @cpsr.thumb
         log "Fetch pc: #{hex_str @r[15]}, instr: #{hex_str @gba.bus.read_half(@r[15]).to_u16}"
@@ -141,17 +148,8 @@ class CPU
 
   @[AlwaysInline]
   def set_reg(reg : Int, value : UInt32) : UInt32
-    case reg
-    when 15
-      if @cpsr.thumb
-        @r[reg] = value & ~1
-      else
-        @r[reg] = value & ~3
-      end
-      clear_pipeline
-    else @r[reg] = value
-    end
-    value
+    clear_pipeline if reg == 15
+    @r[reg] = value
   end
 
   @[AlwaysInline]

src/crab/mmio.cr

@@ -50,7 +50,7 @@ class MMIO
       @waitcnt.value = (@waitcnt.value & mask) | value.to_u16 << shift
     elsif not_used? io_addr
     else
-      puts "Unmapped MMIO write ~ addr:#{hex_str io_addr.to_u32}, val:#{value}".colorize(:yellow)
+      puts "Unmapped MMIO write ~ addr:#{hex_str index.to_u32}, val:#{hex_str value}".colorize(:yellow)
     end
   end