Calculate dead instructions when a live interval is created.

This gets us closer to being able to remove LiveVariables entirely which is where dead instructions are currently tagged as such.

Reviewed by Jakob Olesen

llvm-svn: 210132

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/include/llvm/CodeGen/LiveIntervalAnalysis.h b/llvm/include/llvm/CodeGen/LiveIntervalAnalysis.h
index ddd623c2a33..176665bc256 100644
--- a/llvm/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/llvm/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -155,6 +155,17 @@ namespace llvm {
     bool shrinkToUses(LiveInterval *li,
                       SmallVectorImpl<MachineInstr*> *dead = nullptr);
 
+    /// \brief Walk the values in the given interval and compute which ones
+    /// are dead.  Dead values are not deleted, however:
+    /// - Dead PHIDef values are marked as unused.
+    /// - New dead machine instructions are added to the dead vector.
+    /// - CanSeparate is set to true if the interval may have been separated
+    ///   into multiple connected components.
+    void computeDeadValues(LiveInterval *li,
+                           LiveRange &LR,
+                           bool *CanSeparate,
+                           SmallVectorImpl<MachineInstr*> *dead);
+
     /// extendToIndices - Extend the live range of LI to reach all points in
     /// Indices. The points in the Indices array must be jointly dominated by
     /// existing defs in LI. PHI-defs are added as needed to maintain SSA form.