SystemZ target - Incorrect code generated for accessing thread_local variables when high-word feature is enabled

[uweigand]

Summary

I came across a bug in the generated code for SystemZ target when accessing thread_local variables in functions that have 7 or more parameters.

The problem can be seen here
https://godbolt.org/z/v77J_p

while extracting the values from AR0 and AR1

ear     %r0, %a0                 ; copy AR0 to GR0L
risblg  %r14, %r0, 0, 159, 32    <<<<<<<< copy GR0H to GR14L
sllg    %r14, %r14, 32
ear     %r0, %a1              
risblg  %r14, %r0, 0, 159, 32    <<<<<<<< the same issue here

the compiler thinks there is an option to copy the content of access registers into high half of the general purpose register, which is not available on the platform.

Bug report: https://bugs.llvm.org/show_bug.cgi?id=44254

[jonpa]

Patch suggested at https://reviews.llvm.org/D75014 with a different approach.

[uweigand]

This was actually fixed in a different way here: https://reviews.llvm.org/D75014
I'm closing this review now.

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

 }
 
 SDValue SystemZTargetLowering::lowerThreadPointer(const SDLoc &DL,
                                                   SelectionDAG &DAG) const {
   SDValue Chain = DAG.getEntryNode();
   EVT PtrVT = getPointerTy(DAG.getDataLayout());
 
   // The high part of the thread pointer is in access register 0.
-  SDValue TPHi = DAG.getCopyFromReg(Chain, DL, SystemZ::A0, MVT::i32);
-  TPHi = DAG.getNode(ISD::ANY_EXTEND, DL, PtrVT, TPHi);
+  SDNode *AR0 = DAG.getMachineNode(SystemZ::EAR, DL, MVT::i32,
+                                   DAG.getRegister(SystemZ::A0, MVT::i32));
+  SDValue TPHi = DAG.getNode(ISD::ANY_EXTEND, DL, PtrVT, SDValue(AR0, 0));
 
   // The low part of the thread pointer is in access register 1.
-  SDValue TPLo = DAG.getCopyFromReg(Chain, DL, SystemZ::A1, MVT::i32);
-  TPLo = DAG.getNode(ISD::ZERO_EXTEND, DL, PtrVT, TPLo);
+  SDNode *AR1 = DAG.getMachineNode(SystemZ::EAR, DL, MVT::i32,
+                                   DAG.getRegister(SystemZ::A1, MVT::i32));
+  SDValue TPLo = DAG.getNode(ISD::ZERO_EXTEND, DL, PtrVT, SDValue(AR1, 0));
 
   // Merge them into a single 64-bit address.
   SDValue TPHiShifted = DAG.getNode(ISD::SHL, DL, PtrVT, TPHi,
                                     DAG.getConstant(32, DL, PtrVT));
   return DAG.getNode(ISD::OR, DL, PtrVT, TPHiShifted, TPLo);
 }
 
 SDValue SystemZTargetLowering::lowerGlobalTLSAddress(GlobalAddressSDNode *Node,