sksl can now fold constant vector or matrix equality expressions

Bug: skia:
Change-Id: Icaddae68e53ed3629bcdc04b5f0b541d9e4398e2
Reviewed-on: https://skia-review.googlesource.com/14260
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/sksl/ir/SkSLExpression.h b/src/sksl/ir/SkSLExpression.h
index 5db9ddf96f..07dad1d7df 100644
--- a/src/sksl/ir/SkSLExpression.h
+++ b/src/sksl/ir/SkSLExpression.h
@@ -48,11 +48,24 @@ struct Expression : public IRNode {
     , fKind(kind)
     , fType(std::move(type)) {}
 
+    /**
+     * Returns true if this expression is constant. compareConstant must be implemented for all
+     * constants!
+     */
     virtual bool isConstant() const {
         return false;
     }
 
     /**
+     * Compares this constant expression against another constant expression of the same type. It is
+     * an error to call this on non-constant expressions, or if the types of the expressions do not
+     * match.
+     */
+    virtual bool compareConstant(const Context& context, const Expression& other) const {
+        ABORT("cannot call compareConstant on this type");
+    }
+
+    /**
      * Returns true if evaluating the expression potentially has side effects. Expressions may never
      * return false if they actually have side effects, but it is legal (though suboptimal) to
      * return true if there are not actually any side effects.