[PowerPC] [NFC] add test for O0 pipeline

[shchenz]

Summary

This is to address comments https://reviews.llvm.org/D138265#3950197

This should be helpful for detecting optimization passes added to O0 pipeline by mistake.

[lkail]

LGTM.

[shchenz]

llvm/test/CodeGen/PowerPC/O0-pipeline.ll

60

This pass seems should not be run at -O0?

[lkail]

llvm/test/CodeGen/PowerPC/O0-pipeline.ll

60

In this pass, we have

if (skipFunction(MF.getFunction()) || !RunPreEmitPeephole) {
  // Remove UNENCODED_NOP even when this pass is disabled.
  // This needs to be done unconditionally so we don't emit zeros
  // in the instruction stream.
  SmallVector<MachineInstr *, 4> InstrsToErase;
  for (MachineBasicBlock &MBB : MF)
    for (MachineInstr &MI : MBB)
      if (MI.getOpcode() == PPC::UNENCODED_NOP)
        InstrsToErase.push_back(&MI);
  for (MachineInstr *MI : InstrsToErase)
    MI->eraseFromParent();
  return false;
}

So I think it's essential to guarantee correct codegen.

llvm/test/CodeGen/PowerPC/O0-pipeline.ll

+; RUN: llc --debugify-and-strip-all-safe=0 -mtriple=powerpc64-- -O0 \
+; RUN:   -debug-pass=Structure < %s -o /dev/null 2>&1 | \
+; RUN:   grep -v "Verify generated machine code" | FileCheck %s
+
+; REQUIRES: asserts
+
+; CHECK-LABEL: Pass Arguments:
+; CHECK-NEXT: Target Library Information
+; CHECK-NEXT: Target Pass Configuration
+; CHECK-NEXT: Machine Module Information
+; CHECK-NEXT: Target Transform Information
+; CHECK-NEXT: Create Garbage Collector Module Metadata
+; CHECK-NEXT: Assumption Cache Tracker
+; CHECK-NEXT: Profile summary info
+; CHECK-NEXT: Machine Branch Probability Analysis
+; CHECK-NEXT:   ModulePass Manager
+; CHECK-NEXT:     Pre-ISel Intrinsic Lowering
+; CHECK-NEXT:     FunctionPass Manager
+; CHECK-NEXT:       Expand large div/rem
+; CHECK-NEXT:       Expand large fp convert
+; CHECK-NEXT:       Expand Atomic instructions
+; CHECK-NEXT:     PPC Lower MASS Entries
+; CHECK-NEXT:     FunctionPass Manager
+; CHECK-NEXT:       Module Verifier
+; CHECK-NEXT:       Lower Garbage Collection Instructions
+; CHECK-NEXT:       Shadow Stack GC Lowering
+; CHECK-NEXT:       Lower constant intrinsics
+; CHECK-NEXT:       Remove unreachable blocks from the CFG
+; CHECK-NEXT:       Expand vector predication intrinsics
+; CHECK-NEXT:       Scalarize Masked Memory Intrinsics
+; CHECK-NEXT:       Expand reduction intrinsics
+; CHECK-NEXT:       Exception handling preparation
+; CHECK-NEXT:       Safe Stack instrumentation pass
+; CHECK-NEXT:       Insert stack protectors
+; CHECK-NEXT:       Module Verifier
+; CHECK-NEXT:       PowerPC DAG->DAG Pattern Instruction Selection
+; CHECK-NEXT:       PowerPC VSX Copy Legalization
+; CHECK-NEXT:       Finalize ISel and expand pseudo-instructions
+; CHECK-NEXT:       Local Stack Slot Allocation
+; CHECK-NEXT:       Remove unreachable machine basic blocks
+; CHECK-NEXT:       Live Variable Analysis
+; CHECK-NEXT:       MachineDominator Tree Construction
+; CHECK-NEXT:       Slot index numbering
+; CHECK-NEXT:       Live Interval Analysis
+; CHECK-NEXT:       PowerPC TLS Dynamic Call Fixup
+; CHECK-NEXT:       PowerPC TOC Register Dependencies
+; CHECK-NEXT:       Eliminate PHI nodes for register allocation
+; CHECK-NEXT:       Two-Address instruction pass
+; CHECK-NEXT:       Fast Register Allocator
+; CHECK-NEXT:       Remove Redundant DEBUG_VALUE analysis
+; CHECK-NEXT:       Fixup Statepoint Caller Saved
+; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
+; CHECK-NEXT:       Machine Optimization Remark Emitter
+; CHECK-NEXT:       Prologue/Epilogue Insertion & Frame Finalization
+; CHECK-NEXT:       Post-RA pseudo instruction expansion pass
+; CHECK-NEXT:       Analyze Machine Code For Garbage Collection
+; CHECK-NEXT:       Insert fentry calls
+; CHECK-NEXT:       Insert XRay ops
+; CHECK-NEXT:       Implement the 'patchable-function' attribute
+; CHECK-NEXT:       PowerPC Pre-Emit Peephole
+; CHECK-NEXT:       PowerPC Expand ISEL Generation
+; CHECK-NEXT:       Contiguously Lay Out Funclets
+; CHECK-NEXT:       StackMap Liveness Analysis
+; CHECK-NEXT:       Live DEBUG_VALUE analysis
+; CHECK-NEXT:       PowerPC Expand Atomic
+; CHECK-NEXT:       PowerPC Branch Selector
+; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
+; CHECK-NEXT:       Machine Optimization Remark Emitter
+; CHECK-NEXT:       Linux PPC Assembly Printer
+; CHECK-NEXT:       Free MachineFunction
+
+define void @f() {
+  ret void
+}