[X86] Make isel select the 2-byte register form of INC/DEC even in non-64-bit mode. Convert to the 1-byte form in non-64-bit mode as part of MCInst lowering.
Overall this seems simpler. It reduces duplication of patterns between both modes and it simplifies the memory folding/unfolding tables as they don't need to create fake instructions just to keep track of 64-bitness.
llvm-svn: 225252
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 759416d..63ccded 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -545,6 +545,24 @@
break;
}
+ case X86::DEC16r:
+ case X86::DEC32r:
+ case X86::INC16r:
+ case X86::INC32r:
+ // If we aren't in 64-bit mode we can use the 1-byte inc/dec instructions.
+ if (!AsmPrinter.getSubtarget().is64Bit()) {
+ unsigned Opcode;
+ switch (OutMI.getOpcode()) {
+ default: llvm_unreachable("Invalid opcode");
+ case X86::DEC16r: Opcode = X86::DEC16r_alt; break;
+ case X86::DEC32r: Opcode = X86::DEC32r_alt; break;
+ case X86::INC16r: Opcode = X86::INC16r_alt; break;
+ case X86::INC32r: Opcode = X86::INC32r_alt; break;
+ }
+ OutMI.setOpcode(Opcode);
+ }
+ break;
+
// These are pseudo-ops for OR to help with the OR->ADD transformation. We do
// this with an ugly goto in case the resultant OR uses EAX and needs the
// short form.