thumb: Fix misimplementation of THUMB 12 :(

And this kids, is why you don't ever assume what an instruction does
without reading the manual.
Also, I called the ThumbFormat enum variant "LdrAddress", so I went
ahead and implemented as an ldr_str :/


Former-commit-id: f13833d16fba07565a0aba9d247d9754dbfc3d39

src/arm7tdmi/thumb/display.rs

@@ -163,7 +163,7 @@ impl ThumbInstruction {
         )
     }
 
-    fn fmt_thumb_ldr_address(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt_thumb_load_address(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
             f,
             "add\t{Rd}, {r}, #{Imm:#x}",
@@ -291,7 +291,7 @@ impl fmt::Display for ThumbInstruction {
             ThumbFormat::LdrStrImmOffset => self.fmt_thumb_ldr_str_imm_offset(f),
             ThumbFormat::LdrStrHalfWord => self.fmt_thumb_ldr_str_halfword(f),
             ThumbFormat::LdrStrSp => self.fmt_thumb_ldr_str_sp(f),
-            ThumbFormat::LdrAddress => self.fmt_thumb_ldr_address(f),
+            ThumbFormat::LoadAddress => self.fmt_thumb_load_address(f),
             ThumbFormat::AddSp => self.fmt_thumb_add_sp(f),
             ThumbFormat::PushPop => self.fmt_thumb_push_pop(f),
             ThumbFormat::LdmStm => self.fmt_thumb_ldm_stm(f),

src/arm7tdmi/thumb/exec.rs

@@ -266,13 +266,15 @@ impl Core {
         self.do_exec_thumb_ldr_str_with_addr(bus, insn, addr)
     }
 
-    fn exec_thumb_ldr_address(&mut self, bus: &mut Bus, insn: ThumbInstruction) -> CpuExecResult {
+    fn exec_thumb_load_address(&mut self, bus: &mut Bus, insn: ThumbInstruction) -> CpuExecResult {
-        let addr = if insn.flag(ThumbInstruction::FLAG_SP) {
+        let result = if insn.flag(ThumbInstruction::FLAG_SP) {
             self.gpr[REG_SP] + (insn.word8() as Addr)
         } else {
             (insn.pc & !0b10) + 4 + (insn.word8() as Addr)
         };
-        self.do_exec_thumb_ldr_str_with_addr(bus, insn, addr)
+        self.gpr[insn.rd()] = result;
+
+        Ok(CpuPipelineAction::IncPC)
     }
 
     fn do_exec_thumb_ldr_str_with_addr(
@@ -415,7 +417,7 @@ impl Core {
             ThumbFormat::LdrStrImmOffset => self.exec_thumb_ldr_str_imm_offset(bus, insn),
             ThumbFormat::LdrStrHalfWord => self.exec_thumb_ldr_str_halfword(bus, insn),
             ThumbFormat::LdrStrSp => self.exec_thumb_ldr_str_sp(bus, insn),
-            ThumbFormat::LdrAddress => self.exec_thumb_ldr_address(bus, insn),
+            ThumbFormat::LoadAddress => self.exec_thumb_load_address(bus, insn),
             ThumbFormat::AddSp => self.exec_thumb_add_sp(bus, insn),
             ThumbFormat::PushPop => self.exec_thumb_push_pop(bus, insn),
             ThumbFormat::LdmStm => self.exec_thumb_ldm_stm(bus, insn),

src/arm7tdmi/thumb/mod.rs

@@ -61,7 +61,7 @@ pub enum ThumbFormat {
     /// Format 11
     LdrStrSp,
     /// Format 12
-    LdrAddress,
+    LoadAddress,
     /// Format 13
     AddSp,
     /// Format 14
@@ -116,7 +116,7 @@ impl InstructionDecoder for ThumbInstruction {
         } else if raw & 0xf000 == 0x9000 {
             Ok(LdrStrSp)
         } else if raw & 0xf000 == 0xa000 {
-            Ok(LdrAddress)
+            Ok(LoadAddress)
         } else if raw & 0xff00 == 0xb000 {
             Ok(AddSp)
         } else if raw & 0xf600 == 0xb400 {
@@ -208,7 +208,7 @@ impl ThumbInstruction {
             ThumbFormat::DataProcessImm
             | ThumbFormat::LdrPc
             | ThumbFormat::LdrStrSp
-            | ThumbFormat::LdrAddress => self.raw.bit_range(8..11) as usize,
+            | ThumbFormat::LoadAddress => self.raw.bit_range(8..11) as usize,
             _ => (self.raw & 0b111) as usize,
         }
     }