sksl programs can now directly query GLSL caps

This adds support for querying "sk_Caps.<cap>" directly from within an SkSL program.
Combined with the existing support for collapsing 'if' statements with constant tests,
this means we can query caps using ordinary 'if' statements and the tests will 
collapse out at compile time.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4795

Change-Id: I24d716a7fe6abf1489760bf08189164264269076
Reviewed-on: https://skia-review.googlesource.com/4795
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/src/sksl/SkSLIRGenerator.h b/src/sksl/SkSLIRGenerator.h
index d7bd59ad02..5b56689517 100644
--- a/src/sksl/SkSLIRGenerator.h
+++ b/src/sksl/SkSLIRGenerator.h
@@ -49,6 +49,28 @@
 
 namespace SkSL {
 
+struct CapValue {
+    CapValue()
+    : fKind(kInt_Kind)
+    , fValue(-1) {
+        ASSERT(false);
+    }
+
+    CapValue(bool b)
+    : fKind(kBool_Kind)
+    , fValue(b) {}
+
+    CapValue(int i)
+    : fKind(kInt_Kind)
+    , fValue(i) {}
+
+    enum {
+        kBool_Kind,
+        kInt_Kind,
+    } fKind;
+    int fValue;
+};
+
 /**
  * Performs semantic analysis on an abstract syntax tree (AST) and produces the corresponding 
  * (unoptimized) intermediate representation (IR).
@@ -67,6 +89,17 @@ public:
                                                                   const ASTModifiersDeclaration& m);
 
 private:
+    /**
+     * Prepare to compile a program. Pushes a new symbol table and installs the caps so that
+     * references to sk_Caps.<cap> can be resolved.
+     */
+    void start(std::unordered_map<SkString, CapValue>* caps);
+
+    /**
+     * Performs cleanup after compilation is complete.
+     */
+    void finish();
+
     void pushSymbolTable();
     void popSymbolTable();
 
@@ -105,6 +138,7 @@ private:
     Modifiers convertModifiers(const ASTModifiers& m);
     std::unique_ptr<Expression> convertPrefixExpression(const ASTPrefixExpression& expression);
     std::unique_ptr<Statement> convertReturn(const ASTReturnStatement& r);
+    std::unique_ptr<Expression> getCap(Position position, SkString name);
     std::unique_ptr<Expression> convertSuffixExpression(const ASTSuffixExpression& expression);
     std::unique_ptr<Expression> convertField(std::unique_ptr<Expression> base, 
                                              const SkString& field);
@@ -120,6 +154,7 @@ private:
 
     const Context& fContext;
     const FunctionDeclaration* fCurrentFunction;
+    const std::unordered_map<SkString, CapValue>* fCapsMap;
     std::shared_ptr<SymbolTable> fSymbolTable;
     int fLoopLevel;
     ErrorReporter& fErrors;