[PowerPC] Remove zexts after byte-swapping loads
lhbrx and lwbrx not only load their data with byte swapping, but also clear the
upper 32 bits (at least). As a result, they can be added to the PPCISelDAGToDAG
peephole optimization as frontier instructions for the removal of unnecessary
zero extensions.
llvm-svn: 225189
diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index 7d7f557..3e787be 100644
--- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -3729,6 +3729,13 @@
return true;
}
+ // LHBRX and LWBRX always clear the higher-order bits.
+ if (Op32.getMachineOpcode() == PPC::LHBRX ||
+ Op32.getMachineOpcode() == PPC::LWBRX) {
+ ToPromote.insert(Op32.getNode());
+ return true;
+ }
+
// Next, check for those instructions we can look through.
// Assuming the mask does not wrap around, then the higher-order bits are
@@ -3916,6 +3923,8 @@
case PPC::SRW: NewOpcode = PPC::SRW8; break;
case PPC::LI: NewOpcode = PPC::LI8; break;
case PPC::LIS: NewOpcode = PPC::LIS8; break;
+ case PPC::LHBRX: NewOpcode = PPC::LHBRX8; break;
+ case PPC::LWBRX: NewOpcode = PPC::LWBRX8; break;
case PPC::RLWIMI: NewOpcode = PPC::RLWIMI8; break;
case PPC::OR: NewOpcode = PPC::OR8; break;
case PPC::SELECT_I4: NewOpcode = PPC::SELECT_I8; break;