From c5d385d6643e157d6f90d3608004f0f37b64ab75 Mon Sep 17 00:00:00 2001
From: Nebuleon Fumika
Date: Mon, 31 Dec 2012 13:46:47 -0500
Subject: MIPS requires 2-byte reads to be aligned to even addresses. #define
 FAST_ALIGNED_LSB_WORD_ACCESS and use it to read absolute 24-bit addresses as
 either 1 byte & 1 halfword, or 1 halfword & 1 byte.

---
 source/cpuaddr.h | 10 ++++++++++
 source/port.h    |  5 +++++
 2 files changed, 15 insertions(+)

(limited to 'source')

diff --git a/source/cpuaddr.h b/source/cpuaddr.h
index 34fb41b..91a0347 100644
--- a/source/cpuaddr.h
+++ b/source/cpuaddr.h
@@ -256,6 +256,11 @@ static void AbsoluteLong (AccessMode a, InternalOp op)
     long Addr;
 #ifdef FAST_LSB_WORD_ACCESS
     Addr = (*(uint32 *) CPU.PC) & 0xffffff;
+#elif defined FAST_ALIGNED_LSB_WORD_ACCESS
+    if (((int) CPU.PC & 1) == 0)
+        Addr = (*(uint16 *) CPU.PC) + (*(CPU.PC + 2) << 16);
+    else
+        Addr = *CPU.PC + ((*(uint16 *) (CPU.PC + 1)) << 8);
 #else
     Addr = *CPU.PC + (*(CPU.PC + 1) << 8) + (*(CPU.PC + 2) << 16);
 #endif
@@ -434,6 +439,11 @@ static void AbsoluteLongIndexedX (AccessMode a, InternalOp op)
     long Addr;
 #ifdef FAST_LSB_WORD_ACCESS
     Addr = (*(uint32 *) CPU.PC + ICPU.Registers.X.W) & 0xffffff;
+#elif defined FAST_ALIGNED_LSB_WORD_ACCESS
+    if (((int) CPU.PC & 1) == 0)
+        Addr = ((*(uint16 *) CPU.PC) + (*(CPU.PC + 2) << 16) + ICPU.Registers.X.W) & 0xFFFFFF;
+    else
+        Addr = (*CPU.PC + ((*(uint16 *) (CPU.PC + 1)) << 8) + ICPU.Registers.X.W) & 0xFFFFFF;
 #else
     Addr = (*CPU.PC + (*(CPU.PC + 1) << 8) + (*(CPU.PC + 2) << 16) + ICPU.Registers.X.W) & 0xffffff;
 #endif
diff --git a/source/port.h b/source/port.h
index 5b94d06..1e34410 100644
--- a/source/port.h
+++ b/source/port.h
@@ -274,6 +274,11 @@ EXTERN_C void MixSound(void);
     defined(__WIN32__) || defined(__alpha__)
 #define LSB_FIRST
 #define FAST_LSB_WORD_ACCESS
+#elif defined(__MIPSEL__)
+#define LSB_FIRST
+// On little-endian MIPS, a 16-bit word can be read directly from an address
+// only if it's aligned.
+#define FAST_ALIGNED_LSB_WORD_ACCESS
 #else
 //#define MSB_FIRST
 #define LSB_FIRST
-- 
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