From 5749cd3a2497443d520ff91f38ec699c87c21e5a Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Sat, 24 Oct 2020 16:00:12 -0700
Subject: [PATCH] abstract register writing (always align and clear pipeline on
 pc writes)

---
 src/crab/arm/block_data_transfer.cr           |  8 ++----
 src/crab/arm/branch.cr                        |  5 ++--
 src/crab/arm/branch_exchange.cr               |  5 ++--
 src/crab/arm/data_processing.cr               | 25 +++++++++---------
 src/crab/arm/halfword_data_transfer_imm.cr    | 12 ++++-----
 src/crab/arm/halfword_data_transfer_reg.cr    | 12 ++++-----
 src/crab/arm/multiply.cr                      |  4 +--
 src/crab/arm/multiply_long.cr                 |  4 +--
 src/crab/arm/psr_transfer.cr                  |  4 +--
 src/crab/arm/single_data_swap.cr              |  4 +--
 src/crab/arm/single_data_transfer.cr          | 10 +++----
 src/crab/arm/software_interrupt.cr            |  5 ++--
 src/crab/cpu.cr                               | 15 +++++++++++
 src/crab/display.cr                           |  1 +
 src/crab/thumb/add_offset_to_stack_pointer.cr |  4 +--
 src/crab/thumb/add_subtract.cr                |  4 +--
 src/crab/thumb/alu_operations.cr              | 26 +++++++++----------
 src/crab/thumb/conditional_branch.cr          |  3 +--
 src/crab/thumb/hi_reg_branch_exchange.cr      | 10 +++----
 src/crab/thumb/load_address.cr                |  2 +-
 src/crab/thumb/load_store_halfword.cr         |  2 +-
 src/crab/thumb/load_store_immediate_offset.cr |  8 ++----
 src/crab/thumb/load_store_register_offset.cr  |  8 ++----
 src/crab/thumb/load_store_sign_extended.cr    |  8 +++---
 src/crab/thumb/long_branch_link.cr            |  7 +++--
 src/crab/thumb/move_compare_add_subtract.cr   |  6 ++---
 src/crab/thumb/move_shifted_register.cr       | 12 ++++-----
 src/crab/thumb/multiple_load_store.cr         |  4 +--
 src/crab/thumb/pc_relative_load.cr            |  2 +-
 src/crab/thumb/push_pop_registers.cr          |  7 +++--
 src/crab/thumb/software_interrupt.cr          |  5 ++--
 src/crab/thumb/sp_relative_load_store.cr      |  2 +-
 src/crab/thumb/thumb.cr                       |  2 +-
 src/crab/thumb/unconditional_branch.cr        |  3 +--
 34 files changed, 116 insertions(+), 123 deletions(-)

diff --git a/src/crab/arm/block_data_transfer.cr b/src/crab/arm/block_data_transfer.cr
index f1b2e36..71cb007 100644
--- a/src/crab/arm/block_data_transfer.cr
+++ b/src/crab/arm/block_data_transfer.cr
@@ -14,8 +14,7 @@ module ARM
       16.times do |idx|
         if bit?(list, idx)
           address &+= add ? 4 : -4 if pre_index
-          @r[idx] = @gba.bus.read_word(address)
-          clear_pipeline if idx == 15
+          set_reg(idx, @gba.bus.read_word(address))
           address &+= add ? 4 : -4 unless pre_index
         end
       end
@@ -29,9 +28,6 @@ module ARM
       end
     end
 
-    if write_back
-      @r[rn] = address
-      clear_pipeline if rn == 15 # do this for all other instrs that write to r15
-    end
+    set_reg(rn, address) if write_back
   end
 end
diff --git a/src/crab/arm/branch.cr b/src/crab/arm/branch.cr
index bf26d15..02d733e 100644
--- a/src/crab/arm/branch.cr
+++ b/src/crab/arm/branch.cr
@@ -3,8 +3,7 @@ module ARM
     link = bit?(instr, 24)
     offset = instr & 0xFFFFFF
     offset = (offset << 8).to_i32! >> 6
-    @r[14] = @r[15] - 4 if link
-    @r[15] &+= offset
-    clear_pipeline
+    set_reg(14, @r[15] - 4) if link
+    set_reg(15, @r[15] &+ offset)
   end
 end
diff --git a/src/crab/arm/branch_exchange.cr b/src/crab/arm/branch_exchange.cr
index 1555078..6587fe6 100644
--- a/src/crab/arm/branch_exchange.cr
+++ b/src/crab/arm/branch_exchange.cr
@@ -3,10 +3,9 @@ module ARM
     rn = bits(instr, 0..3)
     if bit?(@r[rn], 0)
       @cpsr.thumb = true
-      @r[15] = @r[rn] & ~1
+      set_reg(15, @r[rn])
     else
-      @r[15] = @r[rn] & ~3
+      set_reg(15, @r[rn])
     end
-    clear_pipeline
   end
 end
diff --git a/src/crab/arm/data_processing.cr b/src/crab/arm/data_processing.cr
index 2e7b7ca..87a026d 100644
--- a/src/crab/arm/data_processing.cr
+++ b/src/crab/arm/data_processing.cr
@@ -12,28 +12,27 @@ module ARM
                 end
     # todo handle carry flag on all ops
     case opcode
-    when 0x0 then res = @r[rd] = @r[rn] & operand_2
-    when 0x1 then res = @r[rd] = @r[rn] ^ operand_2
-    when 0x2 then res = @r[rd] = sub(@r[rn], operand_2, set_conditions)
-    when 0x3 then res = @r[rd] = sub(operand_2, @r[rn], set_conditions)
-    when 0x4 then res = @r[rd] = add(@r[rn], operand_2, set_conditions)
-    when 0x5 then res = @r[rd] = adc(@r[rn], operand_2, set_conditions)
-    when 0x6 then res = @r[rd] = sbc(@r[rn], operand_2, set_conditions)
-    when 0x7 then res = @r[rd] = sbc(operand_2, @r[rn], set_conditions)
+    when 0x0 then res = set_reg(rd, @r[rn] & operand_2)
+    when 0x1 then res = set_reg(rd, @r[rn] ^ operand_2)
+    when 0x2 then res = set_reg(rd, sub(@r[rn], operand_2, set_conditions))
+    when 0x3 then res = set_reg(rd, sub(operand_2, @r[rn], set_conditions))
+    when 0x4 then res = set_reg(rd, add(@r[rn], operand_2, set_conditions))
+    when 0x5 then res = set_reg(rd, adc(@r[rn], operand_2, set_conditions))
+    when 0x6 then res = set_reg(rd, sbc(@r[rn], operand_2, set_conditions))
+    when 0x7 then res = set_reg(rd, sbc(operand_2, @r[rn], set_conditions))
     when 0x8 then res = @r[rn] & operand_2
     when 0x9 then res = @r[rn] ^ operand_2
     when 0xA then res = sub(@r[rn], operand_2, set_conditions)
     when 0xB then res = add(@r[rn], operand_2, set_conditions)
-    when 0xC then res = @r[rd] = @r[rn] | operand_2
-    when 0xD then res = @r[rd] = operand_2
-    when 0xE then res = @r[rd] = @r[rn] & ~operand_2
-    when 0xF then res = @r[rd] = ~operand_2
+    when 0xC then res = set_reg(rd, @r[rn] | operand_2)
+    when 0xD then res = set_reg(rd, operand_2)
+    when 0xE then res = set_reg(rd, @r[rn] & ~operand_2)
+    when 0xF then res = set_reg(rd, ~operand_2)
     else          raise "Unimplemented execution of data processing opcode: #{hex_str opcode}"
     end
     if set_conditions # todo this only works for logical ops, not arithmetic
       @cpsr.zero = res == 0
       @cpsr.negative = bit?(res, 31)
     end
-    clear_pipeline if rd == 15 # todo only do this when needed (not 0xA or 0xB)
   end
 end
diff --git a/src/crab/arm/halfword_data_transfer_imm.cr b/src/crab/arm/halfword_data_transfer_imm.cr
index d94dead..b092f53 100644
--- a/src/crab/arm/halfword_data_transfer_imm.cr
+++ b/src/crab/arm/halfword_data_transfer_imm.cr
@@ -25,25 +25,25 @@ module ARM
     when 0b00 # swp, no docs on this?
     when 0b01 # ldrh/strh
       if load
-        @r[rd] = @gba.bus.read_half address
+        set_reg(rd, @gba.bus.read_half address)
       else
         @gba.bus[address] = 0xFFFF_u16 & @r[rd]
       end
     when 0b10 # ldrsb
-      @r[rd] = @gba.bus[address].to_i8!.to_u32
+      set_reg(rd, @gba.bus[address].to_i8!.to_u32)
     when 0b11 # ldrsh
-      @r[rd] = @gba.bus.read_half(address).to_i16!.to_u32
+      set_reg(rd, @gba.bus.read_half(address).to_i16!.to_u32)
     else raise "Invalid halfword data transfer imm op: #{sh}"
     end
 
     if !pre_index
       if add
-        @r[rn] &+= offset
+        set_reg(rn, @r[rn] &+ offset)
       else
-        @r[rn] &-= offset
+        set_reg(rn, @r[rn] &- offset)
       end
     elsif write_back
-      @r[rn] = address
+      set_reg(rn, address)
     end
   end
 end
diff --git a/src/crab/arm/halfword_data_transfer_reg.cr b/src/crab/arm/halfword_data_transfer_reg.cr
index ce39d8b..9bd1cb8 100644
--- a/src/crab/arm/halfword_data_transfer_reg.cr
+++ b/src/crab/arm/halfword_data_transfer_reg.cr
@@ -24,25 +24,25 @@ module ARM
     when 0b00 # swp, no docs on this?
     when 0b01 # ldrh/strh
       if load
-        @r[rd] = @gba.bus.read_half address
+        set_reg(rd, @gba.bus.read_half address)
       else
         @gba.bus[address] = 0xFFFF_u16 & @r[rd]
       end
     when 0b10 # ldrsb
-      @r[rd] = @gba.bus[address].to_i8!.to_u32
+      set_reg(rd, @gba.bus[address].to_i8!.to_u32)
     when 0b11 # ldrsh
-      @r[rd] = @gba.bus.read_half(address).to_i16!.to_u32
+      set_reg(rd, @gba.bus.read_half(address).to_i16!.to_u32)
     else raise "Invalid halfword data transfer imm op: #{sh}"
     end
 
     if !pre_index
       if add
-        @r[rn] &+= offset
+        set_reg(rn, @r[rn] &+ offset)
       else
-        @r[rn] &-= offset
+        set_reg(rn, @r[rn] &- offset)
       end
     elsif write_back
-      @r[rn] = address
+      set_reg(rn, address)
     end
   end
 end
diff --git a/src/crab/arm/multiply.cr b/src/crab/arm/multiply.cr
index bb05179..91eef3b 100644
--- a/src/crab/arm/multiply.cr
+++ b/src/crab/arm/multiply.cr
@@ -7,8 +7,8 @@ module ARM
     rs = bits(instr, 8..11)
     rm = bits(instr, 0..3)
 
-    @r[rd] = @r[rm] &* @r[rs]
-    @r[rd] &+= @r[rn] if accumulate
+    set_reg(rd, @r[rm] &* @r[rs])
+    set_reg(rd, @r[rd] &+ @r[rn]) if accumulate
     if set_conditions
       @cpsr.zero = @r[rd] == 0
       @cpsr.negative = bit?(@r[rd], 31)
diff --git a/src/crab/arm/multiply_long.cr b/src/crab/arm/multiply_long.cr
index c6173e9..6a63c94 100644
--- a/src/crab/arm/multiply_long.cr
+++ b/src/crab/arm/multiply_long.cr
@@ -14,8 +14,8 @@ module ARM
             @r[rm].to_u64 &* @r[rs]
           end
     res &+= @r[rdhi].to_u64 << 32 | @r[rdlo] if accumulate
-    @r[rdhi] = (res >> 32).to_u32!
-    @r[rdlo] = res.to_u32!
+    set_reg(rdhi, (res >> 32).to_u32!)
+    set_reg(rdlo, res.to_u32!)
     if set_conditions
       @cpsr.zero = res == 0
       @cpsr.negative = bit?(@r[rdhi], 31)
diff --git a/src/crab/arm/psr_transfer.cr b/src/crab/arm/psr_transfer.cr
index 2d874c0..e7b8179 100644
--- a/src/crab/arm/psr_transfer.cr
+++ b/src/crab/arm/psr_transfer.cr
@@ -27,9 +27,9 @@ module ARM
     else
       rd = bits(instr, 12..15)
       if spsr
-        @r[rd] = @spsr.value
+        set_reg(rd, @spsr.value)
       else
-        @r[rd] = @cpsr.value
+        set_reg(rd, @cpsr.value)
       end
     end
   end
diff --git a/src/crab/arm/single_data_swap.cr b/src/crab/arm/single_data_swap.cr
index 92e1654..9563708 100644
--- a/src/crab/arm/single_data_swap.cr
+++ b/src/crab/arm/single_data_swap.cr
@@ -7,11 +7,11 @@ module ARM
     if byte_quantity
       tmp = @gba.bus[@r[rn]]
       @gba.bus[@r[rn]] = @r[rm].to_u8!
-      @r[rd] = tmp.to_u32
+      set_reg(rd, tmp.to_u32)
     else
       tmp = @gba.bus.read_word @r[rn]
       @gba.bus[@r[rn]] = @r[rm]
-      @r[rd] = tmp
+      set_reg(rd, tmp)
     end
   end
 end
diff --git a/src/crab/arm/single_data_transfer.cr b/src/crab/arm/single_data_transfer.cr
index 77796f8..1fc5fc3 100644
--- a/src/crab/arm/single_data_transfer.cr
+++ b/src/crab/arm/single_data_transfer.cr
@@ -27,9 +27,9 @@ module ARM
 
     if load
       if byte_quantity
-        @r[rd] = 0xFF_u32 & @gba.bus[address]
+        set_reg(rd, 0xFF_u32 & @gba.bus[address])
       else
-        @r[rd] = @gba.bus.read_word address
+        set_reg(rd, @gba.bus.read_word address)
       end
     else
       if byte_quantity
@@ -41,12 +41,12 @@ module ARM
 
     if !pre_indexing
       if add_offset
-        @r[rn] &+= offset
+        set_reg(rn, @r[rn] &+ offset)
       else
-        @r[rn] &-= offset
+        set_reg(rn, @r[rn] &- offset)
       end
     elsif write_back
-      @r[rn] = address
+      set_reg(rn, address)
     end
   end
 end
diff --git a/src/crab/arm/software_interrupt.cr b/src/crab/arm/software_interrupt.cr
index f95bebf..3179210 100644
--- a/src/crab/arm/software_interrupt.cr
+++ b/src/crab/arm/software_interrupt.cr
@@ -2,9 +2,8 @@ module ARM
   def arm_software_interrupt(instr : Word) : Nil
     lr = @r[15] - 4
     switch_mode CPU::Mode::SVC
-    @r[14] = lr
+    set_reg(14, lr)
     @cpsr.irq_disable = true
-    @r[15] = 0x08
-    clear_pipeline
+    set_reg(15, 0x08)
   end
 end
diff --git a/src/crab/cpu.cr b/src/crab/cpu.cr
index 6630495..c6eb90e 100644
--- a/src/crab/cpu.cr
+++ b/src/crab/cpu.cr
@@ -134,6 +134,21 @@ class CPU
     end
   end
 
+  @[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
+  end
+
   # Logical shift left
   def lsl(word : Word, bits : Int, set_conditions : Bool) : Word
     log "lsl - word:#{hex_str word}, bits:#{bits}"
diff --git a/src/crab/display.cr b/src/crab/display.cr
index ff50f83..8b58f92 100644
--- a/src/crab/display.cr
+++ b/src/crab/display.cr
@@ -20,6 +20,7 @@ class Display
 
   @fps = 30
   @seconds : Int32 = Time.utc.second
+
   def draw(framebuffer : Bytes) : Nil
     LibSDL.update_texture @texture, nil, framebuffer, WIDTH * 2
     @renderer.clear
diff --git a/src/crab/thumb/add_offset_to_stack_pointer.cr b/src/crab/thumb/add_offset_to_stack_pointer.cr
index a5a8b72..28e39bc 100644
--- a/src/crab/thumb/add_offset_to_stack_pointer.cr
+++ b/src/crab/thumb/add_offset_to_stack_pointer.cr
@@ -3,9 +3,9 @@ module THUMB
     sign = bit?(instr, 7)
     offset = bits(instr, 0..6)
     if sign # negative
-      @r[13] &-= (offset << 2)
+      set_reg(13, @r[13] &- (offset << 2))
     else # positive
-      @r[13] &+= (offset << 2)
+      set_reg(13, @r[13] &+ (offset << 2))
     end
   end
 end
diff --git a/src/crab/thumb/add_subtract.cr b/src/crab/thumb/add_subtract.cr
index 2a14fab..1b01cf7 100644
--- a/src/crab/thumb/add_subtract.cr
+++ b/src/crab/thumb/add_subtract.cr
@@ -11,9 +11,9 @@ module THUMB
                 @r[imm]
               end
     if sub
-      @r[rd] = sub(@r[rs], operand, true)
+      set_reg(rd, sub(@r[rs], operand, true))
     else
-      @r[rd] = add(@r[rs], operand, true)
+      set_reg(rd, add(@r[rs], operand, true))
     end
     # todo handle carry flag on all ops
     @cpsr.zero = @r[rd] == 0
diff --git a/src/crab/thumb/alu_operations.cr b/src/crab/thumb/alu_operations.cr
index 1c9c842..0da2356 100644
--- a/src/crab/thumb/alu_operations.cr
+++ b/src/crab/thumb/alu_operations.cr
@@ -5,22 +5,22 @@ module THUMB
     rd = bits(instr, 0..2)
     # todo handle flags for all ops
     case op
-    when 0b0000 then res = @r[rd] = @r[rd] & @r[rs]
-    when 0b0001 then res = @r[rd] = @r[rd] ^ @r[rs]
-    when 0b0010 then res = @r[rd] = lsl(@r[rd], @r[rs], true)
-    when 0b0011 then res = @r[rd] = lsr(@r[rd], @r[rs], true)
-    when 0b0100 then res = @r[rd] = asr(@r[rd], @r[rs], true)
-    when 0b0101 then res = @r[rd] = adc(@r[rd], @r[rs], true)
-    when 0b0110 then res = @r[rd] = sbc(@r[rd], @r[rs], true)
-    when 0b0111 then res = @r[rd] = ror(@r[rd], @r[rs], true)
+    when 0b0000 then res = set_reg(rd, @r[rd] & @r[rs])
+    when 0b0001 then res = set_reg(rd, @r[rd] ^ @r[rs])
+    when 0b0010 then res = set_reg(rd, lsl(@r[rd], @r[rs], true))
+    when 0b0011 then res = set_reg(rd, lsr(@r[rd], @r[rs], true))
+    when 0b0100 then res = set_reg(rd, asr(@r[rd], @r[rs], true))
+    when 0b0101 then res = set_reg(rd, adc(@r[rd], @r[rs], true))
+    when 0b0110 then res = set_reg(rd, sbc(@r[rd], @r[rs], true))
+    when 0b0111 then res = set_reg(rd, ror(@r[rd], @r[rs], true))
     when 0b1000 then res = @r[rd] & @r[rs]
-    when 0b1001 then res = @r[rd] = (-@r[rs].to_i32!).to_u32!
+    when 0b1001 then res = set_reg(rd, (-@r[rs].to_i32!).to_u32!)
     when 0b1010 then res = sub(@r[rd], @r[rs], true)
     when 0b1011 then res = add(@r[rd], @r[rs], true)
-    when 0b1100 then res = @r[rd] = @r[rd] | @r[rs]
-    when 0b1101 then res = @r[rd] = @r[rs] &* @r[rd]
-    when 0b1110 then res = @r[rd] = @r[rd] & ~@r[rs]
-    when 0b1111 then res = @r[rd] = ~@r[rs]
+    when 0b1100 then res = set_reg(rd, @r[rd] | @r[rs])
+    when 0b1101 then res = set_reg(rd, @r[rs] &* @r[rd])
+    when 0b1110 then res = set_reg(rd, @r[rd] & ~@r[rs])
+    when 0b1111 then res = set_reg(rd, ~@r[rs])
     else             raise "Invalid alu op: #{op}"
     end
     @cpsr.zero = res == 0
diff --git a/src/crab/thumb/conditional_branch.cr b/src/crab/thumb/conditional_branch.cr
index 3477790..bc1dd8b 100644
--- a/src/crab/thumb/conditional_branch.cr
+++ b/src/crab/thumb/conditional_branch.cr
@@ -3,8 +3,7 @@ module THUMB
     cond = bits(instr, 8..11)
     offset = bits(instr, 0..7).to_i8!.to_i32
     if check_cond cond
-      @r[15] &+= (offset * 2)
-      clear_pipeline
+      set_reg(15, @r[15] &+ (offset * 2))
     end
   end
 end
diff --git a/src/crab/thumb/hi_reg_branch_exchange.cr b/src/crab/thumb/hi_reg_branch_exchange.cr
index 13df881..0c40249 100644
--- a/src/crab/thumb/hi_reg_branch_exchange.cr
+++ b/src/crab/thumb/hi_reg_branch_exchange.cr
@@ -10,18 +10,16 @@ module THUMB
     rs += 8 if h2
 
     case op
-    when 0b00 then @r[rd] = add(@r[rd], @r[rs], true)
+    when 0b00 then set_reg(rd, add(@r[rd], @r[rs], true))
     when 0b01 then sub(@r[rd], @r[rs], true)
-    when 0b10 then @r[rd] = @r[rs]
+    when 0b10 then set_reg(rd, @r[rs])
     when 0b11
       if bit?(@r[rs], 0)
-        @r[15] = @r[rs] & ~1
+        set_reg(15, @r[rs])
       else
         @cpsr.thumb = false
-        @r[15] = @r[rs] & ~3
+        set_reg(15, @r[rs])
       end
-      clear_pipeline
     end
-    clear_pipeline if rd == 15
   end
 end
diff --git a/src/crab/thumb/load_address.cr b/src/crab/thumb/load_address.cr
index dbb6ca1..33514eb 100644
--- a/src/crab/thumb/load_address.cr
+++ b/src/crab/thumb/load_address.cr
@@ -4,6 +4,6 @@ module THUMB
     rd = bits(instr, 8..10)
     word = bits(instr, 0..8)
     imm = word << 2
-    @r[rd] = (source ? @r[13] : @r[15]) &+ imm
+    set_reg(rd, (source ? @r[13] : @r[15]) &+ imm)
   end
 end
diff --git a/src/crab/thumb/load_store_halfword.cr b/src/crab/thumb/load_store_halfword.cr
index ed7ef45..8664512 100644
--- a/src/crab/thumb/load_store_halfword.cr
+++ b/src/crab/thumb/load_store_halfword.cr
@@ -6,7 +6,7 @@ module THUMB
     rd = bits(instr, 0..2)
     address = @r[rb] + (offset << 1)
     if load
-      @r[rd] = @gba.bus.read_half(address)
+      set_reg(rd, @gba.bus.read_half(address))
     else
       @gba.bus[address] = @r[rd].to_u16!
     end
diff --git a/src/crab/thumb/load_store_immediate_offset.cr b/src/crab/thumb/load_store_immediate_offset.cr
index 9541933..7004808 100644
--- a/src/crab/thumb/load_store_immediate_offset.cr
+++ b/src/crab/thumb/load_store_immediate_offset.cr
@@ -8,13 +8,9 @@ module THUMB
     address = @r[rb] &+ (offset << 2)
     case byte_quantity_and_load
     when 0b00 then @gba.bus[address] = @r[rd]
-    when 0b01
-      @r[rd] = @gba.bus.read_word(address)
-      clear_pipeline if rd == 15
+    when 0b01 then set_reg(rd, @gba.bus.read_word(address))
     when 0b10 then @gba.bus[address] = 0xFF_u8 & @r[rd]
-    when 0b11
-      @r[rd] = 0xFFFFFFFF_u32 & @gba.bus[address]
-      clear_pipeline if rd == 15
+    when 0b11 then set_reg(rd, 0xFFFFFFFF_u32 & @gba.bus[address])
     end
   end
 end
diff --git a/src/crab/thumb/load_store_register_offset.cr b/src/crab/thumb/load_store_register_offset.cr
index 36ce091..0d335f7 100644
--- a/src/crab/thumb/load_store_register_offset.cr
+++ b/src/crab/thumb/load_store_register_offset.cr
@@ -8,12 +8,8 @@ module THUMB
     case load_and_byte_quantity
     when 0b00 then @gba.bus[address] = @r[rd]
     when 0b01 then @gba.bus[address] = 0xFF_u8 & @r[rd]
-    when 0b10
-      @r[rd] = @gba.bus.read_word address
-      clear_pipeline if rd == 15
-    when 0b11
-      @r[rd] = 0xFFFFFFFF_u32 & @gba.bus[address]
-      clear_pipeline if rd == 15
+    when 0b10 then set_reg(rd, @gba.bus.read_word address)
+    when 0b11 then set_reg(rd, 0xFFFFFFFF_u32 & @gba.bus[address])
     end
   end
 end
diff --git a/src/crab/thumb/load_store_sign_extended.cr b/src/crab/thumb/load_store_sign_extended.cr
index 1db299b..e835a57 100644
--- a/src/crab/thumb/load_store_sign_extended.cr
+++ b/src/crab/thumb/load_store_sign_extended.cr
@@ -6,10 +6,10 @@ module THUMB
     rd = bits(instr, 0..2)
     address = @r[rb] &+ @r[ro]
     case hs
-    when 0b00 then @gba.bus[address] = @r[rd].to_u16!                  # strh
-    when 0b01 then @r[rd] = @gba.bus[address].to_i8!.to_u32            # ldsb
-    when 0b10 then @r[rd] = @gba.bus.read_half(address)                # ldrh
-    when 0b11 then @r[rd] = @gba.bus.read_half(address).to_i16!.to_u32 # ldsh
+    when 0b00 then @gba.bus[address] = @r[rd].to_u16!                      # strh
+    when 0b01 then set_reg(rd, @gba.bus[address].to_i8!.to_u32)            # ldsb
+    when 0b10 then set_reg(rd, @gba.bus.read_half(address))                # ldrh
+    when 0b11 then set_reg(rd, @gba.bus.read_half(address).to_i16!.to_u32) # ldsh
     else           raise "Invalid load/store signed extended: #{hs}"
     end
   end
diff --git a/src/crab/thumb/long_branch_link.cr b/src/crab/thumb/long_branch_link.cr
index 03a7857..9337d8b 100644
--- a/src/crab/thumb/long_branch_link.cr
+++ b/src/crab/thumb/long_branch_link.cr
@@ -4,12 +4,11 @@ module THUMB
     offset = bits(instr, 0..10)
     if second_instr
       temp = @r[15] &- 2
-      @r[15] = @r[14] &+ (offset << 1)
-      @r[14] = temp | 1
-      clear_pipeline
+      set_reg(15, @r[14] &+ (offset << 1))
+      set_reg(14, temp | 1)
     else
       offset = (offset << 5).to_i16! >> 5
-      @r[14] = @r[15] &+ (offset.to_u32 << 12)
+      set_reg(14, @r[15] &+ (offset.to_u32 << 12))
     end
   end
 end
diff --git a/src/crab/thumb/move_compare_add_subtract.cr b/src/crab/thumb/move_compare_add_subtract.cr
index e943d60..afb8c38 100644
--- a/src/crab/thumb/move_compare_add_subtract.cr
+++ b/src/crab/thumb/move_compare_add_subtract.cr
@@ -5,10 +5,10 @@ module THUMB
     offset = bits(instr, 0..7)
     # todo handle carry flag on all ops
     case op
-    when 0b00 then res = @r[rd] = offset
+    when 0b00 then res = set_reg(rd, offset)
     when 0b01 then res = sub(@r[rd], offset, true)
-    when 0b10 then res = @r[rd] = add(@r[rd], offset, true)
-    when 0b11 then res = @r[rd] = sub(@r[rd], offset, true)
+    when 0b10 then res = set_reg(rd, add(@r[rd], offset, true))
+    when 0b11 then res = set_reg(rd, sub(@r[rd], offset, true))
     else           raise "Invalid move/compare/add/subtract op: #{op}"
     end
     @cpsr.zero = res == 0
diff --git a/src/crab/thumb/move_shifted_register.cr b/src/crab/thumb/move_shifted_register.cr
index fde88a9..572fd97 100644
--- a/src/crab/thumb/move_shifted_register.cr
+++ b/src/crab/thumb/move_shifted_register.cr
@@ -4,12 +4,12 @@ module THUMB
     offset = bits(instr, 6..10)
     rs = bits(instr, 3..5)
     rd = bits(instr, 0..2)
-    @r[rd] = case op
-             when 0b00 then lsl(@r[rs], offset, true)
-             when 0b01 then lsr(@r[rs], offset, true)
-             when 0b10 then asr(@r[rs], offset, true)
-             else           raise "Invalid shifted register op: #{op}"
-             end
+    case op
+    when 0b00 then set_reg(rd, lsl(@r[rs], offset, true))
+    when 0b01 then set_reg(rd, lsr(@r[rs], offset, true))
+    when 0b10 then set_reg(rd, asr(@r[rs], offset, true))
+    else           raise "Invalid shifted register op: #{op}"
+    end
     @cpsr.zero = @r[rd] == 0
     @cpsr.negative = bit?(@r[rd], 31)
   end
diff --git a/src/crab/thumb/multiple_load_store.cr b/src/crab/thumb/multiple_load_store.cr
index d347429..8762751 100644
--- a/src/crab/thumb/multiple_load_store.cr
+++ b/src/crab/thumb/multiple_load_store.cr
@@ -7,7 +7,7 @@ module THUMB
     if load # ldmia
       8.times do |idx|
         if bit?(list, idx)
-          @r[idx] = @gba.bus.read_word(address)
+          set_reg(idx, @gba.bus.read_word(address))
           address &+= 4
         end
       end
@@ -19,6 +19,6 @@ module THUMB
         end
       end
     end
-    @r[rb] = address
+    set_reg(rb, address)
   end
 end
diff --git a/src/crab/thumb/pc_relative_load.cr b/src/crab/thumb/pc_relative_load.cr
index 24b318f..75a7d03 100644
--- a/src/crab/thumb/pc_relative_load.cr
+++ b/src/crab/thumb/pc_relative_load.cr
@@ -2,6 +2,6 @@ module THUMB
   def thumb_pc_relative_load(instr : Word) : Nil
     imm = bits(instr, 0..7)
     rd = bits(instr, 8..10)
-    @r[rd] = @gba.bus.read_word((@r[15] & ~2) &+ (imm << 2))
+    set_reg(rd, @gba.bus.read_word((@r[15] & ~2) &+ (imm << 2)))
   end
 end
diff --git a/src/crab/thumb/push_pop_registers.cr b/src/crab/thumb/push_pop_registers.cr
index 17b730b..d3ba4ae 100644
--- a/src/crab/thumb/push_pop_registers.cr
+++ b/src/crab/thumb/push_pop_registers.cr
@@ -7,14 +7,13 @@ module THUMB
     if pop
       8.times do |idx|
         if bit?(list, idx)
-          @r[idx] = @gba.bus.read_word(address)
+          set_reg(idx, @gba.bus.read_word(address))
           address &+= 4
         end
       end
       if pclr
-        @r[15] = @gba.bus.read_word(address)
+        set_reg(15, @gba.bus.read_word(address))
         address &+= 4
-        clear_pipeline
       end
     else
       if pclr
@@ -28,6 +27,6 @@ module THUMB
         end
       end
     end
-    @r[13] = address
+    set_reg(13, address)
   end
 end
diff --git a/src/crab/thumb/software_interrupt.cr b/src/crab/thumb/software_interrupt.cr
index a4d612a..4699de7 100644
--- a/src/crab/thumb/software_interrupt.cr
+++ b/src/crab/thumb/software_interrupt.cr
@@ -2,10 +2,9 @@ module THUMB
   def thumb_software_interrupt(instr : Word) : Nil
     lr = @r[15] - 4
     switch_mode CPU::Mode::SVC
-    @r[14] = lr
+    set_reg(14, lr)
     @cpsr.irq_disable = true
     @cpsr.thumb = false
-    @r[15] = 0x08
-    clear_pipeline
+    set_reg(15, 0x08)
   end
 end
diff --git a/src/crab/thumb/sp_relative_load_store.cr b/src/crab/thumb/sp_relative_load_store.cr
index 5722470..a944195 100644
--- a/src/crab/thumb/sp_relative_load_store.cr
+++ b/src/crab/thumb/sp_relative_load_store.cr
@@ -5,7 +5,7 @@ module THUMB
     word = bits(instr, 0..7)
     address = @r[13] &+ (word << 2)
     if load
-      @r[rd] = @gba.bus.read_word(address)
+      set_reg(rd, @gba.bus.read_word(address))
     else
       @gba.bus[address] = @r[rd]
     end
diff --git a/src/crab/thumb/thumb.cr b/src/crab/thumb/thumb.cr
index dd1561f..b812016 100644
--- a/src/crab/thumb/thumb.cr
+++ b/src/crab/thumb/thumb.cr
@@ -25,7 +25,7 @@ module THUMB
       elsif idx & 0b11110000 == 0b10010000
         lut[idx] = ->thumb_sp_relative_load_store(Word)
       elsif idx & 0b11110000 == 0b10000000
-        lut[idx] = -> thumb_load_store_halfword(Word)
+        lut[idx] = ->thumb_load_store_halfword(Word)
       elsif idx & 0b11100000 == 0b01100000
         lut[idx] = ->thumb_load_store_immediate_offset(Word)
       elsif idx & 0b11110010 == 0b01010010
diff --git a/src/crab/thumb/unconditional_branch.cr b/src/crab/thumb/unconditional_branch.cr
index 62f8f71..7cbde8c 100644
--- a/src/crab/thumb/unconditional_branch.cr
+++ b/src/crab/thumb/unconditional_branch.cr
@@ -2,7 +2,6 @@ module THUMB
   def thumb_unconditional_branch(instr : Word) : Nil
     offset = bits(instr, 0..10)
     offset = (offset << 5).to_i16! >> 4
-    @r[15] &+= offset
-    clear_pipeline
+    set_reg(15, @r[15] &+ offset)
   end
 end