[PowerPC] Only use some extend mne if assembler is modern enough

Legacy AIX assembly might not support all extended mnes,
add one feature bit to control the generation in MC,
and avoid generating them by default on AIX.

Reviewed By: sfertile

Differential Revision: https://reviews.llvm.org/D94458

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index 86816fa..d31195f 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -133,6 +133,8 @@ void PPCSubtarget::initializeEnvironment() {
   UsePPCPostRASchedStrategy = false;
   PairedVectorMemops = false;
   PredictableSelectIsExpensive = false;
+  HasModernAIXAs = false;
+  IsAIX = false;
 
   HasPOPCNTD = POPCNTD_Unavailable;
 }