added constant folding & branch elimination to skslc

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2489673002

Committed: https://skia.googlesource.com/skia/+/6136310ee8f43247548bcefcaeca6d43023c10aa
Review-Url: https://codereview.chromium.org/2489673002

1 files changed, 5 insertions, 0 deletions

diff --git a/src/sksl/SkSLIRGenerator.h b/src/sksl/SkSLIRGenerator.h
index a1b86f4f54..036f24253b 100644
--- a/src/sksl/SkSLIRGenerator.h
+++ b/src/sksl/SkSLIRGenerator.h
@@ -89,6 +89,11 @@ private:
     std::unique_ptr<Statement> convertDiscard(const ASTDiscardStatement& d);
     std::unique_ptr<Statement> convertDo(const ASTDoStatement& d);
     std::unique_ptr<Expression> convertBinaryExpression(const ASTBinaryExpression& expression);
+    // Returns null if it cannot fold the expression. Note that unlike most other functions here, a 
+    // null return does not represent a compilation error.
+    std::unique_ptr<Expression> constantFold(const Expression& left,
+                                             Token::Kind op,
+                                             const Expression& right);
     std::unique_ptr<Extension> convertExtension(const ASTExtension& e);
     std::unique_ptr<Statement> convertExpressionStatement(const ASTExpressionStatement& s);
     std::unique_ptr<Statement> convertFor(const ASTForStatement& f);