explain what earlyclobber actually is.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56415 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineOperand.h b/include/llvm/CodeGen/MachineOperand.h
index 555f320027da7a8f43ee14eb29ca0e1360ea2a21..c2399beaf6eec761166432bdf71966e48b515131 100644 (file)
--- a/include/llvm/CodeGen/MachineOperand.h
+++ b/include/llvm/CodeGen/MachineOperand.h
@@ -68,9 +68,9 @@ private:
   /// This is only valid on definitions of registers.
   bool IsDead : 1;
 
-  /// IsEarlyClobber - True if this MO_Register operand is marked earlyclobber
-  /// in an inline asm.  Flag is not valid for any other case.   See gcc doc
-  /// for description of earlyclobber.
+  /// IsEarlyClobber - True if this MO_Register 'def' operand is written to
+  /// by the MachineInstr before all input registers are read.  This is used to
+  /// model the GCC inline asm '&' constraint modifier.
   bool IsEarlyClobber : 1;
 
   /// OverlapsEarlyClobber - True if this MO_Register operand is used as an