* Implement dominator based loop identification

[oota-llvm.git] / include / llvm / Analysis / InductionVariable.h

diff --git a/include/llvm/Analysis/InductionVariable.h b/include/llvm/Analysis/InductionVariable.h
new file mode 100644 (file)
index 0000000..02fa6de
--- /dev/null
+++ b/include/llvm/Analysis/InductionVariable.h
@@ -0,0 +1,53 @@
+//===- llvm/Analysis/InductionVariable.h - Induction variable ----*- C++ -*--=//
+//
+// This interface is used to identify and classify induction variables that
+// exist in the program.  Induction variables must contain a PHI node that
+// exists in a loop header.  Because of this, they are identified an managed by
+// this PHI node.
+//
+// Induction variables are classified into a type.  Knowing that an induction
+// variable is of a specific type can constrain the values of the start and
+// step.  For example, a SimpleLinear induction variable must have a start and
+// step values that are constants.
+//
+// Induction variables can be created with or without loop information.  If no
+// loop information is available, induction variables cannot be recognized to be
+// more than SimpleLinear variables.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_INDUCTIONVARIABLE_H
+#define LLVM_ANALYSIS_INDUCTIONVARIABLE_H
+
+class Value;
+class PHINode;
+class Instruction;
+namespace cfg { class LoopInfo; class Loop; }
+
+class InductionVariable {
+public:
+  enum iType {               // Identify the type of this induction variable
+    Cannonical,              // Starts at 0, counts by 1
+    SimpleLinear,            // Simple linear: Constant start, constant step
+    Linear,                  // General linear:  loop invariant start, and step
+    Unknown,                 // Unknown type.  Start & Step are null
+  } InductionType;
+  
+  Value *Start, *Step;       // Start and step expressions for this indvar
+  PHINode *Phi;              // The PHI node that corresponds to this indvar
+public:
+
+  // Create an induction variable for the specified value.  If it is a PHI, and
+  // if it's recognizable, classify it and fill in instance variables.
+  //
+  InductionVariable(Instruction *V, cfg::LoopInfo *LoopInfo = 0);
+
+
+  // Classify Induction
+  static enum iType Classify(const Value *Start, const Value *Step,
+                            const cfg::Loop *L = 0);
+                                             
+
+};
+
+#endif