Fix a grammaro and clarify a comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72668 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86Instr64bit.td b/lib/Target/X86/X86Instr64bit.td
index 0babaa46f2d9883682fb41cb685ca1e2d548e80f..dc15e4aa4ee9974956ab4282031e84c4c8184eab 100644 (file)
--- a/lib/Target/X86/X86Instr64bit.td
+++ b/lib/Target/X86/X86Instr64bit.td
@@ -1588,11 +1588,11 @@ def : Pat<(i8 (trunc GR16:$src)),
       Requires<[In64BitMode]>;
 
 // h-register tricks.
-// For now, be conservative and only the extract if the value is immediately
-// zero-extended or stored, which are somewhat common cases. This uses a bunch
-// of code to prevent a register requiring a REX prefix from being allocated in
-// the same instruction as the h register, as there's currently no way to
-// describe this requirement to the register allocator.
+// For now, be conservative on x86-64 and use an h-register extract only if the
+// value is immediately zero-extended or stored, which are somewhat common
+// cases. This uses a bunch of code to prevent a register requiring a REX prefix
+// from being allocated in the same instruction as the h register, as there's
+// currently no way to describe this requirement to the register allocator.
 
 // h-register extract and zero-extend.
 def : Pat<(and (srl_su GR64:$src, (i8 8)), (i64 255)),