nx2: title 4's cutscene scene renders; blit constants for fragment shaders

- Render area falls back to colour target 0 when the surface clip is unset
  (Switch 2 titles may never program it); it feeds the synthesized blit block.
- BlitConstantsPass also covers fragment shaders: UV clamp rectangle 0..1
  (0x30-0x3c) and zero dither bias.
- Debug: EDEN_NX2_SKIP_VS=<addr,...>, EDEN_NX2_TRACE_VS=<addr>,
  EDEN_NX2_UPSCALE_SOURCE[_FORMAT], EDEN_NX2_TRACE_AFTER_UPSCALE,
  EDEN_NX2_SAMPLE_AT, skipped-draw reasons, clear tracing.

Showing the raw HDR scene colour through the upscale fallback gives the
correct lit cockpit scene; the game's tonemap pass still outputs black.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/shader_recompiler/ir_opt/position_pass.cpp b/src/shader_recompiler/ir_opt/position_pass.cpp
index e68e175abc..4890346944 100644
--- a/src/shader_recompiler/ir_opt/position_pass.cpp
+++ b/src/shader_recompiler/ir_opt/position_pass.cpp
@@ -77,9 +77,10 @@ void PositionPass(Environment& env, IR::Program& program) {
 // Switch 2 fullscreen blit vertex shaders read a parameter block from constant bank 24 (lowered to
 // bank 17, which games never bind) that the console provides itself. For a blit covering the whole
 // render target it holds: texel size (0x0/0x4, again at 0x10/0x14), size (0x8/0xc), a UV scale of
-// 1 (0x18/0x1c) and the integer source rectangle 0,0..W-1,H-1 (0x50-0x5c).
+// 1 (0x18/0x1c), the UV clamp rectangle 0,0..1,1 (0x30-0x3c, read by the fragment shader), a zero
+// dither bias (0x40-0x48) and the integer source rectangle 0,0..W-1,H-1 (0x50-0x5c).
 void BlitConstantsPass(Environment& env, IR::Program& program) {
-    if (env.ShaderStage() != Stage::VertexB) {
+    if (env.ShaderStage() != Stage::VertexB && env.ShaderStage() != Stage::Fragment) {
         return;
     }
     bool used{};
@@ -110,6 +111,8 @@ void BlitConstantsPass(Environment& env, IR::Program& program) {
                     return ir.BitCast<IR::U32>(height);
                 case 0x18:
                 case 0x1c:
+                case 0x38:
+                case 0x3c:
                     return ir.Imm32(0x3f800000U);
                 case 0x58:
                     return IR::U32{ir.ConvertFToU(32, ir.FPAdd(width, ir.Imm32(-1.0f)))};