FastISel: avoid function calls between the materialization of the constant and its use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137993 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/FastISel.h b/include/llvm/CodeGen/FastISel.h
index 962a4e2635..18202d93b4 100644
--- a/include/llvm/CodeGen/FastISel.h
+++ b/include/llvm/CodeGen/FastISel.h
@@ -54,8 +54,18 @@ protected:
   const TargetInstrInfo &TII;
   const TargetLowering &TLI;
   const TargetRegisterInfo &TRI;
+
+  /// The position of the last instruction for materializing constants
+  /// for use in the current block. It resets to EmitStartPt when it
+  /// makes sense (for example, it's usually profitable to avoid function
+  /// calls between the definition and the use)
   MachineInstr *LastLocalValue;
 
+  /// The top most instruction in the current block that is allowed for
+  /// emitting local variables. LastLocalValue resets to EmitStartPt when
+  /// it makes sense (for example, on function calls)
+  MachineInstr *EmitStartPt;
+
 public:
   /// getLastLocalValue - Return the position of the last instruction
   /// emitted for materializing constants for use in the current block.
@@ -63,7 +73,10 @@ public:
 
   /// setLastLocalValue - Update the position of the last instruction
   /// emitted for materializing constants for use in the current block.
-  void setLastLocalValue(MachineInstr *I) { LastLocalValue = I; }
+  void setLastLocalValue(MachineInstr *I) {
+    EmitStartPt = I;
+    LastLocalValue = I;
+  }
 
   /// startNewBlock - Set the current block to which generated machine
   /// instructions will be appended, and clear the local CSE map.
@@ -358,6 +371,11 @@ private:
   /// be materialized with new instructions.
   unsigned materializeRegForValue(const Value *V, MVT VT);
 
+  /// flushLocalValueMap - clears LocalValueMap and moves the area for the
+  /// new local variables to the beginning of the block. It helps to avoid
+  /// spilling cached variables across heavy instructions like calls.
+  void flushLocalValueMap();
+
   /// hasTrivialKill - Test whether the given value has exactly one use.
   bool hasTrivialKill(const Value *V) const;
 };