Add getUnrollingPreferences to TTI

Allow targets to customize the default behavior of the generic loop unrolling
transformation. This will be used by the PowerPC backend when targeting the A2
core (which is in-order with a deep pipeline), and using more aggressive
defaults is important.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190542 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 0 deletions

diff --git a/include/llvm/Analysis/TargetTransformInfo.h b/include/llvm/Analysis/TargetTransformInfo.h
index 06810a7de0..eb70e9cdaa 100644
--- a/include/llvm/Analysis/TargetTransformInfo.h
+++ b/include/llvm/Analysis/TargetTransformInfo.h
@@ -29,6 +29,7 @@
 namespace llvm {
 
 class GlobalValue;
+class Loop;
 class Type;
 class User;
 class Value;
@@ -191,6 +192,36 @@ public:
   /// incurs significant execution cost.
   virtual bool isLoweredToCall(const Function *F) const;
 
+  /// Parameters that control the generic loop unrolling transformation.
+  struct UnrollingPreferences {
+    /// The cost threshold for the unrolled loop, compared to
+    /// CodeMetrics.NumInsts aggregated over all basic blocks in the loop body.
+    /// The unrolling factor is set such that the unrolled loop body does not
+    /// exceed this cost. Set this to UINT_MAX to disable the loop body cost
+    /// restriction.
+    unsigned Threshold;
+    /// The cost threshold for the unrolled loop when optimizing for size (set
+    /// to UINT_MAX to disable).
+    unsigned OptSizeThreshold;
+    /// A forced unrolling factor (the number of concatenated bodies of the
+    /// original loop in the unrolled loop body). When set to 0, the unrolling
+    /// transformation will select an unrolling factor based on the current cost
+    /// threshold and other factors.
+    unsigned Count;
+    /// Allow partial unrolling (unrolling of loops to expand the size of the
+    /// loop body, not only to eliminate small constant-trip-count loops).
+    bool     Partial;
+    /// Allow runtime unrolling (unrolling of loops to expand the size of the
+    /// loop body even when the number of loop iterations is not known at compile
+    /// time).
+    bool     Runtime;
+  };
+
+  /// \brief Get target-customized preferences for the generic loop unrolling
+  /// transformation. The caller will initialize UP with the current
+  /// target-independent defaults.
+  virtual void getUnrollingPreferences(Loop *L, UnrollingPreferences &UP) const;
+
   /// @}
 
   /// \name Scalar Target Information