From 09b8876b7387a88655f8c71632cd208830ba72e9 Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Sun, 27 Sep 2020 13:51:17 -0700
Subject: [PATCH] early psr transfer implementation

---
 src/crab/arm/arm.cr          |  2 ++
 src/crab/arm/psr_transfer.cr | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/crab/arm/psr_transfer.cr

diff --git a/src/crab/arm/arm.cr b/src/crab/arm/arm.cr
index bbab8ff..3334249 100644
--- a/src/crab/arm/arm.cr
+++ b/src/crab/arm/arm.cr
@@ -69,6 +69,8 @@ module ARM
         # multiply long
       elsif idx & 0b111111001111 == 0b000000001001
         # multiply
+      elsif idx & 0b110110010000 == 0b000100000000
+        lut[idx] = ->arm_psr_transfer(Word)
       elsif idx & 0b110000000000 == 0b000000000000
         lut[idx] = ->arm_data_processing(Word)
       else
diff --git a/src/crab/arm/psr_transfer.cr b/src/crab/arm/psr_transfer.cr
new file mode 100644
index 0000000..edde956
--- /dev/null
+++ b/src/crab/arm/psr_transfer.cr
@@ -0,0 +1,26 @@
+module ARM
+  def arm_psr_transfer(instr : Word) : Nil
+    # todo respect spsr
+    spsr = bit?(instr, 22)
+    msr = bit?(instr, 21)
+    if msr
+      all = bit?(instr, 16)
+      if all
+        rm = bits(instr, 0..3)
+        @cpsr.value = @r[rm]
+      else
+        imm_flag = bit?(instr, 25)
+        value = if imm_flag
+                  immediate_offset bits(instr, 0..11)
+                else
+                  rm = bits(instr, 0..3)
+                  @r[rm]
+                end
+        @cpsr.value = (@cpsr.value & 0x0FFFFFFF) | (value & 0xF0000000)
+      end
+    else
+      rd = bits(instr, 12..15)
+      @r[rd] = @cpsr.value
+    end
+  end
+end