Shaders: Fix multiplications between 0.0 and inf

The PICA200 semantics for multiplication are so that when multiplying
inf by exactly 0.0, the result is 0.0, instead of NaN, as defined by
IEEE. This is relied upon by games.

Fixes #1024 (missing OoT interface items)

1 files changed, 13 insertions, 1 deletions

diff --git a/src/video_core/pica.h b/src/video_core/pica.h
index 58b924f9e..cf148de50 100644
--- a/src/video_core/pica.h
+++ b/src/video_core/pica.h
@@ -1021,12 +1021,20 @@ struct float24 {
         return ret;
     }
 
+    static float24 Zero() {
+        return FromFloat32(0.f);
+    }
+
     // Not recommended for anything but logging
     float ToFloat32() const {
         return value;
     }
 
     float24 operator * (const float24& flt) const {
+        if ((this->value == 0.f && flt.value == flt.value) ||
+            (flt.value == 0.f && this->value == this->value))
+            // PICA gives 0 instead of NaN when multiplying by inf
+            return Zero();
         return float24::FromFloat32(ToFloat32() * flt.ToFloat32());
     }
 
@@ -1043,7 +1051,11 @@ struct float24 {
     }
 
     float24& operator *= (const float24& flt) {
-        value *= flt.ToFloat32();
+        if ((this->value == 0.f && flt.value == flt.value) ||
+            (flt.value == 0.f && this->value == this->value))
+            // PICA gives 0 instead of NaN when multiplying by inf
+            *this = Zero();
+        else value *= flt.ToFloat32();
         return *this;
     }