[PATCH] [PATCH - review requested] Re-factor code to adjust offset to the memory reference descriptor of an X86 instruction

[Preston Gurd]

Hi sdt,

In the X86 back end, getMemoryOperandNo() returns the offset into the operand array of the start of the memory reference descriptor. 

Additional code in EncodeInstruction provided an additional adjustment. 

This patch places that additional code in a separate function, called getOperandBias, so that any caller of getMemoryOperandNo can also call getOperandBias.

http://llvm-reviews.chandlerc.com/D653

Files:
  lib/Target/X86/MCTargetDesc/X86BaseInfo.h
  lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp

Index: lib/Target/X86/MCTargetDesc/X86BaseInfo.h
===================================================================
--- lib/Target/X86/MCTargetDesc/X86BaseInfo.h
+++ lib/Target/X86/MCTargetDesc/X86BaseInfo.h
@@ -20,6 +20,7 @@
 #include "X86MCTargetDesc.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/MC/MCInstrInfo.h"
 
 namespace llvm {
 
@@ -41,7 +42,6 @@
     AddrNumOperands = 5
   };
 } // end namespace X86;
- 
 
 /// X86II - This namespace holds all of the target specific flags that
 /// instruction info tracks.
@@ -521,6 +521,26 @@
     }
   }
 
+  /// getOperandBias - compute any additional adjustment needed to
+  ///                  the offset to the start of the memory operand
+  ///                  in this instruction.
+  /// If this is a two-address instruction,skip one of the register operands.
+  /// FIXME: This should be handled during MCInst lowering.
+  inline int getOperandBias(const MCInstrDesc& Desc)
+  {
+    unsigned NumOps = Desc.getNumOperands();
+    unsigned CurOp = 0;
+    if (NumOps > 1 && Desc.getOperandConstraint(1, MCOI::TIED_TO) == 0)
+      ++CurOp;
+    else if (NumOps > 3 && Desc.getOperandConstraint(2, MCOI::TIED_TO) == 0) {
+      assert(Desc.getOperandConstraint(NumOps - 1, MCOI::TIED_TO) == 1);
+      // Special case for GATHER with 2 TIED_TO operands
+      // Skip the first 2 operands: dst, mask_wb
+      CurOp += 2;
+    }
+    return CurOp;
+  }
+
   /// getMemoryOperandNo - The function returns the MCInst operand # for the
   /// first field of the memory operand.  If the instruction doesn't have a
   /// memory operand, this returns -1.
Index: lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
===================================================================
--- lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -979,18 +979,8 @@
   if ((TSFlags & X86II::FormMask) == X86II::Pseudo)
     return;
 
-  // If this is a two-address instruction, skip one of the register operands.
-  // FIXME: This should be handled during MCInst lowering.
   unsigned NumOps = Desc.getNumOperands();
-  unsigned CurOp = 0;
-  if (NumOps > 1 && Desc.getOperandConstraint(1, MCOI::TIED_TO) == 0)
-    ++CurOp;
-  else if (NumOps > 3 && Desc.getOperandConstraint(2, MCOI::TIED_TO) == 0) {
-    assert(Desc.getOperandConstraint(NumOps - 1, MCOI::TIED_TO) == 1);
-    // Special case for GATHER with 2 TIED_TO operands
-    // Skip the first 2 operands: dst, mask_wb
-    CurOp += 2;
-  }
+  unsigned CurOp = X86II::getOperandBias(Desc);
 
   // Keep track of the current byte being emitted.
   unsigned CurByte = 0;
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