Inline memove for small constant sizes and refactor memcpy and memset.

src/IceTargetLoweringX86Base.h

Index: src/IceTargetLoweringX86Base.h
diff --git a/src/IceTargetLoweringX86Base.h b/src/IceTargetLoweringX86Base.h
index 342c97b2da5d2d7bb574a2793cf7b916f2b5a104..2c4c7bff7c6808cb13bed266e1b4f7e2aaf3ce66 100644
--- a/src/IceTargetLoweringX86Base.h
+++ b/src/IceTargetLoweringX86Base.h
@@ -153,9 +153,18 @@ protected:
                       Operand *Val);
   void lowerCountZeros(bool Cttz, Type Ty, Variable *Dest, Operand *FirstVal,
                        Operand *SecondVal);
-  /// Replace a call to memcpy with inline instructions.
+  /// If Overflow is false, find the largest type whose width is less than or
+  /// equal to Size. If Overflow is true, find the smallest type whose width can
+  /// be larger than Size. The maximum width can be limited to LimitWidth bytes.
+  Type typeForSize(uint32_t Size, bool overflow = false,

[John, 2015/08/12 17:44:57]

Can this method be made static?

This comment tells me that you have 2 functions inside this one:

typeForSize(args, Overflow) {
  if Overflow:
    return largestTypeSmallerThanSize(args)
  else:
    return firstTypeThatFits(args)

The fact that, at every call site overflow is always a constant is another
pretty strong indication that you want two different functions.

I would also defined a constant named UnlimitedWidth (or NoWidthLimit) and use
it instead of = 0.

[ascull, 2015/08/17 22:18:52]

Done.

+                   uint32_t LimitWidth = 0);
+  /// Copy memory of given type from Src to Dest using OffsetAmt on both.

[John, 2015/08/12 17:44:57]

the lower "prefix" threw me off here. I though there were a high level CopyMem
instruction. What do you thing about renaming this copyMemory?

[ascull, 2015/08/17 22:18:52]

Done.

+  void lowerCopyMem(Type Ty, Variable *Dest, Variable *Src, uint32_t OffsetAmt);
+  /// Replace some calls to memcpy with inline instructions.
   void lowerMemcpy(Operand *Dest, Operand *Src, Operand *Count);
-  /// Replace a call to memset with inline instructions.
+  /// Replace some calls to memmove with inline instructions.
+  void lowerMemmove(Operand *Dest, Operand *Src, Operand *Count);
+  /// Replace some calls to memset with inline instructions.
   void lowerMemset(Operand *Dest, Operand *Val, Operand *Count);
 
   /// Lower an indirect jump adding sandboxing when needed.