Revert "Added constant propagation and better variable liveness tracking to"

This reverts commit f54b07121f81a56145fb118a2e18841fc135717d.

Reason for revert: ASAN failure

Original change's description:
> Added constant propagation and better variable liveness tracking to
> skslc. 
> 
> This allows skslc to track the values of variables with constant
> values across multiple statements and replace variable references with
> constant values where appropriate.
> 
> The improved liveness tracking allows skslc to realize that a
> variable is no longer alive if all references to it have been
> replaced. It is not yet doing much with this information; better
> dead code elimination is coming in a followup change.
> 
> BUG=skia:
> 
> Change-Id: I6bf267d478b769caf0063ac3597dc16bbe618cb4
> Reviewed-on: https://skia-review.googlesource.com/7033
> Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> 

TBR=egdaniel@google.com,ethannicholas@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Change-Id: Id2e26bce96b27df73948f8b32d3dff2e358ae0d6
Reviewed-on: https://skia-review.googlesource.com/7274
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

1 files changed, 8 insertions, 10 deletions

diff --git a/src/sksl/SkSLIRGenerator.h b/src/sksl/SkSLIRGenerator.h
index 2ffcb0df26..13b20fbbcc 100644
--- a/src/sksl/SkSLIRGenerator.h
+++ b/src/sksl/SkSLIRGenerator.h
@@ -88,16 +88,7 @@ public:
     std::unique_ptr<ModifiersDeclaration> convertModifiersDeclaration(
                                                                   const ASTModifiersDeclaration& m);
 
-    /**
-     * If both operands are compile-time constants and can be folded, returns an expression
-     * representing the folded value. Otherwise, returns null. Note that unlike most other functions
-     * here, null does not represent a compilation error.
-     */
-    std::unique_ptr<Expression> constantFold(const Expression& left,
-                                             Token::Kind op,
-                                             const Expression& right) const;
     Program::Inputs fInputs;
-    const Context& fContext;
 
 private:
     /**
@@ -133,6 +124,11 @@ 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);
@@ -155,8 +151,10 @@ private:
     std::unique_ptr<Statement> convertWhile(const ASTWhileStatement& w);
 
     void checkValid(const Expression& expr);
-    void markWrittenTo(const Expression& expr, bool readWrite);
+    void markReadFrom(const Variable& var);
+    void markWrittenTo(const Expression& expr);
 
+    const Context& fContext;
     const FunctionDeclaration* fCurrentFunction;
     const Program::Settings* fSettings;
     std::unordered_map<SkString, CapValue> fCapsMap;