FastISel: don't cache values across the calls (they usually spill on the stack anyway)

include/llvm/CodeGen/FastISel.h

Index: include/llvm/CodeGen/FastISel.h
===================================================================
--- include/llvm/CodeGen/FastISel.h	(revision 137987)
+++ include/llvm/CodeGen/FastISel.h	(working copy)
@@ -54,8 +54,18 @@
   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 @@
 
   /// 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 @@
   /// 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;
 };