[X86][Tablegen] Marking the RSM instruction as defining EFLAGS

[craig.topper]

Doesn't this really Def every register? But its not used by CodeGen so what are we trying to accomplish by adding this?

[cray]

It really does, I should add that to the patch.
Basically, we rely on LLVM's MC backend for static analysis. We have a large stack of patches for the disassembler, and I am trying to break them up to see what the community would like to have upstreamed.

lib/Target/X86/X86InstrSystem.td

   def UD2B    : I<0xB9, RawFrm, (outs), (ins), "ud2b", []>, TB;
 }
 
-def HLT : I<0xF4, RawFrm, (outs), (ins), "hlt", [], IIC_HLT>;
-def RSM : I<0xAA, RawFrm, (outs), (ins), "rsm", [], IIC_RSM>, TB;
+def HLT : I<0xF4, RawFrm, (outs), (ins), "hlt", [], IIC_HLT>;
+
+let Defs = [EFLAGS] in
+  def RSM : I<0xAA, RawFrm, (outs), (ins), "rsm", [], IIC_RSM>, TB;
 
 // Interrupt and SysCall Instructions.
 let Uses = [EFLAGS] in