[PowerPC][WIP] Recompute liveins after eliminating prime/unprime operations

[shchenz]

llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp

411

This really sounds like a 'hack' for a specific case but hurt other normal cases. For example, machine-verifier knows that a def of a user in the same block is removed by mistake(Using an undefined physical register). But now even the def is removed by mistake, machine verifier still thinks that this is valid MIR because it is told the def is from outside but actually there is also no def outside the block.

[lkail]

Will seek another method that's not hacky.

llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp

bool removeAccPrimeUnprime(MachineBasicBlock &MBB) {
               Candidates[Reg - PPC::ACC0] = nullptr;
           }
         }
       }
 
       for (MachineInstr *MI : InstrsToErase)
         MI->eraseFromParent();
       NumRemovedInPreEmit += InstrsToErase.size();
+      // Fixup liveins to make verifier happy.
+      if (!InstrsToErase.empty()) {
+        LivePhysRegs LPR;
+        MBB.clearLiveIns();
+        computeAndAddLiveIns(LPR, MBB);
+      }
       return !InstrsToErase.empty();
     }
 
     bool runOnMachineFunction(MachineFunction &MF) override {
       // If the user wants to set the DSCR using command-line options,
       // load in the specified value at the start of main.
       if (DSCRValue.getNumOccurrences() > 0 && MF.getName().equals("main") &&
           MF.getFunction().hasExternalLinkage()) {

llvm/test/CodeGen/PowerPC/ppc64-acc-regalloc-bugfix.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64le-unknown-linux-gnu \
 ; RUN:     -mcpu=pwr10 -ppc-vsr-nums-as-vr -ppc-asm-full-reg-names < %s \
 ; RUN:    | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple powerpc64le-unknown-linux-gnu \
+; RUN:     -mcpu=pwr10 -ppc-vsr-nums-as-vr -ppc-asm-full-reg-names \
+; RUN:     -ppc-track-subreg-liveness < %s | FileCheck --check-prefix=SUBREG %s
+
 
 define void @copy_novsrp() local_unnamed_addr {
 ; CHECK-LABEL: copy_novsrp:
 ; CHECK:       # %bb.0: # %dmblvi_entry
 ; CHECK-NEXT:    xxlxor v2, v2, v2
 ; CHECK-NEXT:    xxlxor vs0, vs0, vs0
 ; CHECK-NEXT:    xxlor vs3, v2, v2
 ; CHECK-NEXT:    stxv vs1, 0(0)
+;
+; SUBREG-LABEL: copy_novsrp:
+; SUBREG:       # %bb.0: # %dmblvi_entry
+; SUBREG-NEXT:    xxlxor vs3, vs3, vs3
+; SUBREG-NEXT:    xxlxor vs0, vs0, vs0
+; SUBREG-NEXT:    stxv vs1, 0(0)
 dmblvi_entry:
   %0 = tail call <512 x i1> @llvm.ppc.mma.assemble.acc(<16 x i8> zeroinitializer, <16 x i8> undef, <16 x i8> undef, <16 x i8> zeroinitializer)
   %1 = tail call { <16 x i8>, <16 x i8>, <16 x i8>, <16 x i8> } @llvm.ppc.mma.disassemble.acc(<512 x i1> %0)
   %2 = extractvalue { <16 x i8>, <16 x i8>, <16 x i8>, <16 x i8> } %1, 2
   store <16 x i8> %2, ptr null, align 1
   unreachable
 }
 
 declare <512 x i1> @llvm.ppc.mma.assemble.acc(<16 x i8>, <16 x i8>, <16 x i8>, <16 x i8>)
 declare { <16 x i8>, <16 x i8>, <16 x i8>, <16 x i8> } @llvm.ppc.mma.disassemble.acc(<512 x i1>)