From 7d8e2dccef8019df61d7724277adaa68ed434484 Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Sun, 27 Sep 2020 18:12:04 -0700
Subject: [PATCH] set carry flag from barrel shifter ops (arm & thumb)

---
 src/crab/arm/arm.cr                     | 12 ++++++------
 src/crab/arm/data_processing.cr         |  4 ++--
 src/crab/arm/single_data_transfer.cr    |  2 +-
 src/crab/cpu.cr                         | 16 ++++++++++++----
 src/crab/thumb/move_shifted_register.cr |  7 +++----
 5 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/src/crab/arm/arm.cr b/src/crab/arm/arm.cr
index 6d32bcf..8e8424f 100644
--- a/src/crab/arm/arm.cr
+++ b/src/crab/arm/arm.cr
@@ -68,7 +68,7 @@ module ARM
     puts "Unused instruction: #{hex_str instr}"
   end
 
-  def rotate_register(instr : Word, allow_register_shifts = true) : Word
+  def rotate_register(instr : Word, set_conditions : Bool, allow_register_shifts = true) : Word
     reg = bits(instr, 0..3)
     shift_type = bits(instr, 5..6)
     shift_amount = if allow_register_shifts && bit?(instr, 4)
@@ -79,10 +79,10 @@ module ARM
                      bits(instr, 7..11)
                    end
     case shift_type
-    when 0b00 then lsl(@r[reg], shift_amount)
-    when 0b01 then lsr(@r[reg], shift_amount)
-    when 0b10 then asr(@r[reg], shift_amount)
-    when 0b11 then ror(@r[reg], shift_amount)
+    when 0b00 then lsl(@r[reg], shift_amount, set_conditions)
+    when 0b01 then lsr(@r[reg], shift_amount, set_conditions)
+    when 0b10 then asr(@r[reg], shift_amount, set_conditions)
+    when 0b11 then ror(@r[reg], shift_amount, set_conditions)
     else           raise "Impossible shift type: #{hex_str shift_type}"
     end
   end
@@ -90,6 +90,6 @@ module ARM
   def immediate_offset(instr : Word) : Word
     rotate = bits(instr, 8..11)
     imm = bits(instr, 0..7)
-    ror(imm, 2 * rotate)
+    ror(imm, 2 * rotate, false)
   end
 end
diff --git a/src/crab/arm/data_processing.cr b/src/crab/arm/data_processing.cr
index 4880c24..954d159 100644
--- a/src/crab/arm/data_processing.cr
+++ b/src/crab/arm/data_processing.cr
@@ -5,12 +5,12 @@ module ARM
     set_conditions = bit?(instr, 20)
     rn = bits(instr, 16..19)
     rd = bits(instr, 12..15)
-    # todo set carry flag from barrel shifter
     operand_2 = if imm_flag # Operand 2 is an immediate
                   immediate_offset bits(instr, 0..11)
                 else # Operand 2 is a register
-                  rotate_register bits(instr, 0..11)
+                  rotate_register bits(instr, 0..11), set_conditions
                 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
diff --git a/src/crab/arm/single_data_transfer.cr b/src/crab/arm/single_data_transfer.cr
index 2955937..5b787ad 100644
--- a/src/crab/arm/single_data_transfer.cr
+++ b/src/crab/arm/single_data_transfer.cr
@@ -10,7 +10,7 @@ module ARM
     rn = bits(instr, 16..19)
     rd = bits(instr, 12..15)
     operand_2 = if imm_flag # Operand 2 is a register (opposite of data procesing for some reason)
-                  rotate_register bits(instr, 0..11), allow_register_shifts: false
+                  rotate_register bits(instr, 0..11), set_conditions: false, allow_register_shifts: false
                 else # Operand 2 is an immediate offset
                   immediate_offset bits(instr, 0..11)
                 end
diff --git a/src/crab/cpu.cr b/src/crab/cpu.cr
index a019369..1cbc74b 100644
--- a/src/crab/cpu.cr
+++ b/src/crab/cpu.cr
@@ -83,22 +83,30 @@ class CPU
   end
 
   # Logical shift left
-  def lsl(word : Word, bits : Int) : Word
+  def lsl(word : Word, bits : Int, set_conditions : Bool) : Word
+    log "lsl - word:#{hex_str word}, bits:#{bits}"
+    @cpsr.carry = bit?(word, 32 - bits) if set_conditions
     word << bits
   end
 
   # Logical shift right
-  def lsr(word : Word, bits : Int) : Word
+  def lsr(word : Word, bits : Int, set_conditions : Bool) : Word
+    log "lsr - word:#{hex_str word}, bits:#{bits}"
+    @cpsr.carry = bit?(word, bits - 1) if set_conditions
     word >> bits
   end
 
   # Arithmetic shift right
-  def asr(word : Word, bits : Int) : Word
+  def asr(word : Word, bits : Int, set_conditions : Bool) : Word
+    log "asr - word:#{hex_str word}, bits:#{bits}"
+    @cpsr.carry = bit?(word, bits - 1) if set_conditions
     word // (2 ** bits)
   end
 
   # Rotate right
-  def ror(word : Word, bits : Int) : Word
+  def ror(word : Word, bits : Int, set_conditions : Bool) : Word
+    log "ror - word:#{hex_str word}, bits:#{bits}"
+    @cpsr.carry = bit?(word, bits - 1) if set_conditions
     word >> bits | word << (32 - bits)
   end
 
diff --git a/src/crab/thumb/move_shifted_register.cr b/src/crab/thumb/move_shifted_register.cr
index 5fec274..fde88a9 100644
--- a/src/crab/thumb/move_shifted_register.cr
+++ b/src/crab/thumb/move_shifted_register.cr
@@ -1,14 +1,13 @@
 module THUMB
   def thumb_move_shifted_register(instr : Word) : Nil
-    # todo carry flags (currently first divergence on armwrestler)
     op = bits(instr, 11..12)
     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)
-             when 0b01 then lsr(@r[rs], offset)
-             when 0b10 then asr(@r[rs], offset)
+             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
     @cpsr.zero = @r[rd] == 0