Revert "Added dead variable / code elimination to skslc."

This reverts commit 113628d76176a1ab3e6719c59efff23cd10ab213.

Reason for revert: Looks to have caused https://bugs.chromium.org/p/chromium/issues/detail?id=688939

Original change's description:
> 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>
> 

TBR=egdaniel@google.com,benjaminwagner@google.com,ethannicholas@google.com,reviews@skia.org
# Not skipping CQ checks because original CL landed > 1 day ago.
BUG=skia:

Change-Id: I85599e4ca2bc6bfd782edc163f67b64195d6ae65
Reviewed-on: https://skia-review.googlesource.com/8077
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

1 files changed, 6 insertions, 16 deletions

diff --git a/src/sksl/ir/SkSLVariableReference.h b/src/sksl/ir/SkSLVariableReference.h
index 75b7f3dcd4..fecb04e2e5 100644
--- a/src/sksl/ir/SkSLVariableReference.h
+++ b/src/sksl/ir/SkSLVariableReference.h
@@ -38,7 +38,7 @@ struct VariableReference : public Expression {
         }
     }
 
-    ~VariableReference() override {
+    virtual ~VariableReference() override {
         if (fRefKind != kWrite_RefKind) {
             fVariable.fReadCount--;
         }
@@ -64,19 +64,13 @@ struct VariableReference : public Expression {
         fRefKind = refKind;
     }
 
-    bool hasSideEffects() const override {
-        return false;
-    }
-
     SkString description() const override {
         return fVariable.fName;
     }
 
-    std::unique_ptr<Expression> constantPropagate(const IRGenerator& irGenerator,
-                                                  const DefinitionMap& definitions) override {
-        if (fRefKind != kRead_RefKind) {
-            return nullptr;
-        }
+    virtual std::unique_ptr<Expression> constantPropagate(
+                                                        const IRGenerator& irGenerator,
+                                                        const DefinitionMap& definitions) override {
         auto exprIter = definitions.find(&fVariable);
         if (exprIter != definitions.end() && exprIter->second) {
             const Expression* expr = exprIter->second->get();
@@ -91,11 +85,6 @@ struct VariableReference : public Expression {
                                                                    irGenerator.fContext,
                                                                    Position(),
                                                                    ((FloatLiteral*) expr)->fValue));
-                case Expression::kBoolLiteral_Kind:
-                    return std::unique_ptr<Expression>(new BoolLiteral(
-                                                                    irGenerator.fContext,
-                                                                    Position(),
-                                                                    ((BoolLiteral*) expr)->fValue));
                 default:
                     break;
             }
@@ -104,9 +93,10 @@ struct VariableReference : public Expression {
     }
 
     const Variable& fVariable;
-    RefKind fRefKind;
 
 private:
+    RefKind fRefKind;
+
     typedef Expression INHERITED;
 };