Don't use nopl in cpus that don't support it.

Patch by Mikulas Patocka. I added the test. I checked that for cpu names that
gas knows about, it also doesn't generate nopl.

The modified cpus:
i686 - there are i686-class CPUs that don't have nopl: Via c3, Transmeta
        Crusoe, Microsoft VirtualBox - see
        https://bbs.archlinux.org/viewtopic.php?pid=775414
k6, k6-2, k6-3, winchip-c6, winchip2 - these are 586-class CPUs
via c3 c3-2 - see https://bugs.archlinux.org/task/19733 as a proof that
        Via c3 and c3-Nehemiah don't have nopl

llvm-svn: 195679

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index c1a710be5c2..1c6f07121d9 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
@@ -309,8 +309,12 @@ bool X86AsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
 
   // This CPU doesnt support long nops. If needed add more.
   // FIXME: Can we get this from the subtarget somehow?
+  // FIXME: We could generated something better than plain 0x90.
   if (CPU == "generic" || CPU == "i386" || CPU == "i486" || CPU == "i586" ||
-      CPU == "pentium" || CPU == "pentium-mmx" || CPU == "geode") {
+      CPU == "pentium" || CPU == "pentium-mmx" || CPU == "i686" ||
+      CPU == "k6" || CPU == "k6-2" || CPU == "k6-3" || CPU == "geode" ||
+      CPU == "winchip-c6" || CPU == "winchip2" || CPU == "c3" ||
+      CPU == "c3-2") {
     for (uint64_t i = 0; i < Count; ++i)
       OW->Write8(0x90);
     return true;