[Verifier][NFC] Refactor check for associated metadata to allow multiple operands on AIX

[tingwang]

Summary

Currently associated metadata is limited to have single operand.

Patch https://reviews.llvm.org/D125095 intends to use associated metadata to express the associations between global objects on AIX. The association could be one to multiple, for example one static variable could have associated with init and term functions.

This patch intends to setup context to check multiple operands for TT.isOSAIX().

[arsenm]

Missing tests and associated langref changes

[tingwang]

Address comments:
(1) Add test case to show how associated metadata will be used on AIX (currently not supported, marked with XFAIL).
(2) Add langref changes to explain.

[arsenm]

Missing verifier test in llvm/test/Verifier (e.g., the ones I added in 87f2e9448e82bbed4ac59bb61bea03256aa5f4de)

clang/test/CodeGen/PowerPC/aix-init-ref-null.cpp

2 ↗

(On Diff #504952)

A test run with not and a specific error message check is more reliable

[tingwang]

Address comments:
(1) Duplicated associated test cases to make copies for AIX XCOFF, and added multiple operands and null operand as legal cases.
(2) Updated verifier logic to check for AIX target.
(3) Moved XFAIL check to specific lines.

[tingwang]

clang/test/CodeGen/PowerPC/aix-init-ref-null.cpp

2 ↗

(On Diff #504952)

Thank you Matt! Currently there is no error message for this case, so I moved the XFAIL to CHECK lines. Hope that is fine.

[tingwang]

Add empty case in Verifier/associated-metadata-aix-xcoff.ll

[arsenm]

clang/test/CodeGen/PowerPC/aix-init-ref-null.cpp

1 ↗

(On Diff #505709)

Don't use -O3, maybe -O1 -disable-llvm-passes

1 ↗

(On Diff #505709)

Use generated checks with --check-globals?

22 ↗

(On Diff #505709)

XFAIL-CHECK doesn't do anything

clang/test/CodeGen/PowerPC/aix-ref-static-var.cpp

11 ↗

(On Diff #505709)

XFAIL-CHECK doesn't do anything

[tingwang]

Hi Matt @arsenm, thank you for your comments, and I will incorporate your suggestions in the next version.

Since the review process of dependent patch https://reviews.llvm.org/D125095 didn't get any progress for a while..., I'm worried that discussing the verification logic maybe a little bit early. I plan to suspend this patch until I got any progress on D125095. Thank you!

llvm/lib/IR/Verifier.cpp

if (MaybeAlign A = GO->getAlign()) {
       Check(A->value() <= Value::MaximumAlignment,
             "huge alignment values are unsupported", GO);
     }
 
     if (const MDNode *Associated =
             GO->getMetadata(LLVMContext::MD_associated)) {
       Check(Associated->getNumOperands() == 1,
             "associated metadata must have one operand", &GV, Associated);
-      const Metadata *Op = Associated->getOperand(0).get();
-      Check(Op, "associated metadata must have a global value", GO, Associated);
+      auto CheckAssocOperand = [this, &GV, GO, Associated](const Metadata *Op) {
+        Check(Op, "associated metadata must have a global value", GO,
+              Associated);
 
         const auto *VM = dyn_cast_or_null<ValueAsMetadata>(Op);
-      Check(VM, "associated metadata must be ValueAsMetadata", GO, Associated);
+        Check(VM, "associated metadata must be ValueAsMetadata", GO,
+              Associated);
         if (VM) {
           Check(isa<PointerType>(VM->getValue()->getType()),
                 "associated value must be pointer typed", GV, Associated);
 
           const Value *Stripped = VM->getValue()->stripPointerCastsAndAliases();
           Check(isa<GlobalObject>(Stripped) || isa<Constant>(Stripped),
-              "associated metadata must point to a GlobalObject", GO, Stripped);
+                "associated metadata must point to a GlobalObject", GO,
+                Stripped);
           Check(Stripped != GO,
                 "global values should not associate to themselves", GO,
                 Associated);
         }
+      };
+
+      for (unsigned i = 0, e = Associated->getNumOperands(); i != e; ++i)
+        CheckAssocOperand(Associated->getOperand(i).get());
     }
   }
   Check(!GV.hasAppendingLinkage() || isa<GlobalVariable>(GV),
         "Only global variables can have appending linkage!", &GV);
 
   if (GV.hasAppendingLinkage()) {
     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(&GV);
     Check(GVar && GVar->getValueType()->isArrayTy(),