Start of expression analysis support

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 60 insertions, 0 deletions

diff --git a/include/llvm/Analysis/Expressions.h b/include/llvm/Analysis/Expressions.h
new file mode 100644
index 0000000000..c21599f18e
--- /dev/null
+++ b/include/llvm/Analysis/Expressions.h
@@ -0,0 +1,60 @@
+//===- llvm/Analysis/Expressions.h - Expression Analysis Utils ---*- C++ -*--=//
+//
+// This file defines a package of expression analysis utilties:
+//
+// ClassifyExpression: Analyze an expression to determine the complexity of the
+//   expression, and which other variables it depends on.  
+// 
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_EXPRESSIONS_H
+#define LLVM_ANALYSIS_EXPRESSIONS_H
+
+#include <assert.h>
+class Value;
+class ConstPoolInt;
+struct ExprAnalysisResult;
+
+// ClassifyExpression: Analyze an expression to determine the complexity of the
+// expression, and which other values it depends on.  
+//
+ExprAnalysisResult ClassifyExpression(Value *Expr);
+
+// ExprAnalysisResult - Represent an expression of the form CONST*VAR+CONST
+// or simpler.  The expression form that yields the least information about the
+// expression is just the Linear form with no offset.
+//
+struct ExprAnalysisResult {
+  enum ExpressionType {
+    Constant,            // Expr is a simple constant, Offset is value
+    Linear,              // Expr is linear expr, Value is Var+Offset
+    ScaledLinear,        // Expr is scaled linear exp, Value is Scale*Var+Offset
+  } ExprType;
+
+  const ConstPoolInt *Offset;  // Offset of expr, or null if 0
+  Value              *Var;     // Var referenced, if Linear or above (null if 0)
+  const ConstPoolInt *Scale;   // Scale of var if ScaledLinear expr (null if 1)
+
+  inline ExprAnalysisResult(const ConstPoolInt *CPV = 0) {
+    Offset = CPV; Var = 0; Scale = 0;
+    ExprType = Constant;
+  }
+  inline ExprAnalysisResult(Value *Val) {
+    Var = Val; Offset = Scale = 0;
+    ExprType = Var ? Linear : Constant;
+  }
+  inline ExprAnalysisResult(const ConstPoolInt *scale, Value *var, 
+			    const ConstPoolInt *offset) {
+    assert(!(Scale && !Var) && "Can't have scaled nonvariable!");
+    Scale = scale; Var = var; Offset = offset;
+    ExprType = Scale ? ScaledLinear : (Var ? Linear : Constant);
+  }
+
+
+private:
+  friend ExprAnalysisResult ClassifyExpression(Value *);
+  inline ExprAnalysisResult operator+(const ConstPoolInt *Offset);
+  
+};
+
+#endif