Added dead variable / code elimination to skslc.

BUG=skia:

Change-Id: Ib037730803a8f222f099de0e001fe06ad452a22c
Reviewed-on: https://skia-review.googlesource.com/7584
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/sksl/ir/SkSLExpression.h b/src/sksl/ir/SkSLExpression.h
index f87d810fc0..5db9ddf96f 100644
--- a/src/sksl/ir/SkSLExpression.h
+++ b/src/sksl/ir/SkSLExpression.h
@@ -53,6 +53,13 @@ struct Expression : public IRNode {
     }
 
     /**
+     * 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.
+     */
+    virtual bool hasSideEffects() const = 0;
+
+    /**
      * Given a map of known constant variable values, substitute them in for references to those
      * variables occurring in this expression and its subexpressions.  Similar simplifications, such
      * as folding a constant binary expression down to a single value, may also be performed.