From 8c24c86a49b23086941814e3ae1d58a2993dac7a Mon Sep 17 00:00:00 2001
From: jdgleaver
Date: Thu, 15 Oct 2020 14:37:46 +0100
Subject: Backports: Colour operations from Snes9x 1.60 + MIPS optimisations
 from PocketSNES

---
 source/gfx.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

(limited to 'source/gfx.h')

diff --git a/source/gfx.h b/source/gfx.h
index 582f7c2..096ea98 100644
--- a/source/gfx.h
+++ b/source/gfx.h
@@ -33,8 +33,11 @@ typedef struct
    uint32_t    Pitch;
 
    int32_t     Delta;
+#if defined(PSP)
+   /* PSP uses pre-1.60 colour operations */
    uint16_t*   X2;
    uint16_t*   ZERO_OR_X2;
+#endif
    uint16_t*   ZERO;
    uint32_t    RealPitch;  /* True pitch of Screen buffer. */
    uint32_t    Pitch2;     /* Same as RealPitch except while using speed up hack for Glide. */
@@ -148,12 +151,31 @@ extern uint8_t mul_brightness [16][32];
 
 static INLINE uint16_t COLOR_ADD(uint16_t C1, uint16_t C2)
 {
+#if defined(PSP)
+   /* PSP uses pre-1.60 colour operations */
    if (C1 == 0)
       return C2;
    else if (C2 == 0)
       return C1;
    else
       return GFX.X2[(((C1 & RGB_REMOVE_LOW_BITS_MASK) + (C2 & RGB_REMOVE_LOW_BITS_MASK)) >> 1) + (C1 & C2 & RGB_LOW_BITS_MASK)] | ((C1 ^ C2) & RGB_LOW_BITS_MASK);
+#else
+	const int RED_MASK   = 0x1F << RED_SHIFT_BITS;
+	const int GREEN_MASK = 0x1F << GREEN_SHIFT_BITS;
+	const int BLUE_MASK  = 0x1F;
+
+	int rb          = (C1 & (RED_MASK | BLUE_MASK)) + (C2 & (RED_MASK | BLUE_MASK));
+	int rbcarry     = rb & ((0x20 << RED_SHIFT_BITS) | (0x20 << 0));
+	int g           = (C1 & (GREEN_MASK)) + (C2 & (GREEN_MASK));
+	int rgbsaturate = (((g & (0x20 << GREEN_SHIFT_BITS)) | rbcarry) >> 5) * 0x1f;
+	uint16_t retval = (rb & (RED_MASK | BLUE_MASK)) | (g & GREEN_MASK) | rgbsaturate;
+
+#if GREEN_SHIFT_BITS == 6
+	retval         |= (retval & 0x0400) >> 5;
+#endif
+
+	return retval;
+#endif
 }
 
 #define COLOR_ADD1_2(C1, C2) \
@@ -161,11 +183,31 @@ static INLINE uint16_t COLOR_ADD(uint16_t C1, uint16_t C2)
           ((C2) & RGB_REMOVE_LOW_BITS_MASK)) >> 1) + \
          (((C1) & (C2) & RGB_LOW_BITS_MASK) | ALPHA_BITS_MASK))
 
+#if defined(PSP)
+/* PSP uses pre-1.60 colour operations */
 #define COLOR_SUB(C1, C2) \
 (GFX.ZERO_OR_X2 [(((C1) | RGB_HI_BITS_MASKx2) - \
                   ((C2) & RGB_REMOVE_LOW_BITS_MASK)) >> 1] + \
                   ((C1) & RGB_LOW_BITS_MASK) - \
                   ((C2) & RGB_LOW_BITS_MASK))
+#else
+static INLINE uint16_t COLOR_SUB(uint16_t C1, uint16_t C2)
+{
+	int rb1         = (C1 & (THIRD_COLOR_MASK | FIRST_COLOR_MASK)) | ((0x20 << 0) | (0x20 << RED_SHIFT_BITS));
+	int rb2         = C2 & (THIRD_COLOR_MASK | FIRST_COLOR_MASK);
+	int rb          = rb1 - rb2;
+	int rbcarry     = rb & ((0x20 << RED_SHIFT_BITS) | (0x20 << 0));
+	int g           = ((C1 & (SECOND_COLOR_MASK)) | (0x20 << GREEN_SHIFT_BITS)) - (C2 & (SECOND_COLOR_MASK));
+	int rgbsaturate = (((g & (0x20 << GREEN_SHIFT_BITS)) | rbcarry) >> 5) * 0x1f;
+	uint16_t retval = ((rb & (THIRD_COLOR_MASK | FIRST_COLOR_MASK)) | (g & SECOND_COLOR_MASK)) & rgbsaturate;
+
+#if GREEN_SHIFT_BITS == 6
+	retval         |= (retval & 0x0400) >> 5;
+#endif
+
+	return retval;
+}
+#endif
 
 #define COLOR_SUB1_2(C1, C2) \
 GFX.ZERO [(((C1) | RGB_HI_BITS_MASKx2) - \
-- 
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