BPMemory: Make TevKSel more clear

It stores both the konst selection value for alpha and color channels (for two tev stages per ksel), and half of a swap table row (there are 4 total swap tables, which can be used for swizzling the rasterized color and the texture color, and indices selecting which tables to use are stored per tev stage in the alpha combiner).  Since these are indexed very differently, the old code was hard to follow.

Source/Core/VideoCommon/BPMemory.h

@@ -11,6 +11,7 @@
 #include "Common/BitUtils.h"
 #include "Common/CommonTypes.h"
 #include "Common/EnumFormatter.h"
+#include "Common/EnumMap.h"
 #include "Common/Inline.h"
 
 // X.h defines None to be 0 and Always to be 2, which causes problems with some of the enums
@@ -1838,6 +1839,19 @@ struct fmt::formatter<TevReg>
   }
 };
 
+enum class ColorChannel : u32
+{
+  Red = 0,
+  Green = 1,
+  Blue = 2,
+  Alpha = 3,
+};
+template <>
+struct fmt::formatter<ColorChannel> : EnumFormatter<ColorChannel::Alpha>
+{
+  formatter() : EnumFormatter({"Red", "Green", "Blue", "Alpha"}) {}
+};
+
 enum class KonstSel : u32
 {
   V1 = 0,
@@ -1912,16 +1926,13 @@ struct fmt::formatter<KonstSel> : EnumFormatter<KonstSel::K3_A>
 
 union TevKSel
 {
-  BitField<0, 2, u32> swap1;
-  BitField<2, 2, u32> swap2;
-  BitField<4, 5, KonstSel> kcsel0;
-  BitField<9, 5, KonstSel> kasel0;
-  BitField<14, 5, KonstSel> kcsel1;
-  BitField<19, 5, KonstSel> kasel1;
+  BitField<0, 2, ColorChannel> swap_rb;  // Odd ksel number: red; even: blue
+  BitField<2, 2, ColorChannel> swap_ga;  // Odd ksel number: green; even: alpha
+  BitField<4, 5, KonstSel> kcsel_even;
+  BitField<9, 5, KonstSel> kasel_even;
+  BitField<14, 5, KonstSel> kcsel_odd;
+  BitField<19, 5, KonstSel> kasel_odd;
   u32 hex;
-
-  KonstSel getKC(int i) const { return i ? kcsel1.Value() : kcsel0.Value(); }
-  KonstSel getKA(int i) const { return i ? kasel1.Value() : kasel0.Value(); }
 };
 template <>
 struct fmt::formatter<TevKSel>
@@ -1933,8 +1944,36 @@ struct fmt::formatter<TevKSel>
     return fmt::format_to(ctx.out(),
                           "Swap 1: {}\nSwap 2: {}\nColor sel 0: {}\nAlpha sel 0: {}\n"
                           "Color sel 1: {}\nAlpha sel 1: {}",
-                          ksel.swap1, ksel.swap2, ksel.kcsel0, ksel.kasel0, ksel.kcsel1,
-                          ksel.kasel1);
+                          ksel.swap_rb, ksel.swap_ga, ksel.kcsel_even, ksel.kasel_even,
+                          ksel.kcsel_odd, ksel.kasel_odd);
+  }
+};
+
+struct AllTevKSels
+{
+  std::array<TevKSel, 8> ksel;
+
+  KonstSel GetKonstColor(u32 tev_stage) const
+  {
+    const u32 ksel_num = tev_stage >> 1;
+    const bool odd = tev_stage & 1;
+    const auto& cur_ksel = ksel[ksel_num];
+    return odd ? cur_ksel.kcsel_odd.Value() : cur_ksel.kcsel_even.Value();
+  }
+  KonstSel GetKonstAlpha(u32 tev_stage) const
+  {
+    const u32 ksel_num = tev_stage >> 1;
+    const bool odd = tev_stage & 1;
+    const auto& cur_ksel = ksel[ksel_num];
+    return odd ? cur_ksel.kasel_odd.Value() : cur_ksel.kasel_even.Value();
+  }
+  Common::EnumMap<ColorChannel, ColorChannel::Alpha> GetSwapTable(u32 swap_table_id) const
+  {
+    const u32 rg_ksel_num = swap_table_id << 1;
+    const u32 ba_ksel_num = rg_ksel_num + 1;
+    const auto& rg_ksel = ksel[rg_ksel_num];
+    const auto& ba_ksel = ksel[ba_ksel_num];
+    return {rg_ksel.swap_rb, rg_ksel.swap_ga, ba_ksel.swap_rb, ba_ksel.swap_ga};
   }
 };
 
@@ -2415,7 +2454,7 @@ struct BPMemory
   AlphaTest alpha_test;               // 0xf3
   ZTex1 ztex1;                        // 0xf4
   ZTex2 ztex2;                        // 0xf5
-  TevKSel tevksel[8];                 // 0xf6-0xfd
+  AllTevKSels tevksel;                // 0xf6-0xfd
   u32 bpMask;                         // 0xfe
   u32 unknown18;                      // 0xff