[SafepointIRVerifier] Add verifier pass for finding GC relocation bugs

Original Patch and summary by Philip Reames.

RewriteStatepointsForGC tries to rewrite a function in a manner where
the optimizer can't end up using a pointer value after it might have
been relocated by a safepoint. This pass checks the invariant that
RSForGC is supposed to establish and that (if we constructed semantics
correctly) later passes must preserve.

This has been a really useful diagnostic tool when initially developing
the rewriting scheme and has found numerous bugs.

Differential Revision: https://reviews.llvm.org/D15940

Reviewed by: swaroop.sridhar, mjacob

Subscribers: llvm-commits
llvm-svn: 307112

llvm/include/llvm/IR/SafepointIRVerifier.h

@@ -0,0 +1,35 @@
+//===- SafepointIRVerifier.h - Checks for GC relocation problems *- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a verifier which is useful for enforcing the relocation
+// properties required by a relocating GC.  Specifically, it looks for uses of
+// the unrelocated value of pointer SSA values after a possible safepoint. It
+// attempts to report no false negatives, but may end up reporting false
+// positives in rare cases (see the note at the top of the corresponding cpp
+// file.)
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_SAFEPOINT_IR_VERIFIER
+#define LLVM_IR_SAFEPOINT_IR_VERIFIER
+
+namespace llvm {
+
+class Function;
+class FunctionPass;
+
+/// Run the safepoint verifier over a single function.  Crashes on failure.
+void verifySafepointIR(Function &F);
+
+/// Create an instance of the safepoint verifier pass which can be added to
+/// a pass pipeline to check for relocation bugs.
+FunctionPass *createSafepointIRVerifierPass();
+}
+
+#endif // LLVM_IR_SAFEPOINT_IR_VERIFIER

llvm/include/llvm/InitializePasses.h

@@ -318,6 +318,7 @@ void initializeResetMachineFunctionPass(PassRegistry&);
 void initializeReversePostOrderFunctionAttrsLegacyPassPass(PassRegistry&);
 void initializeRewriteStatepointsForGCPass(PassRegistry&);
 void initializeRewriteSymbolsLegacyPassPass(PassRegistry&);
+void initializeSafepointIRVerifierPass(PassRegistry&);
 void initializeSCCPLegacyPassPass(PassRegistry&);
 void initializeSCEVAAWrapperPassPass(PassRegistry&);
 void initializeSLPVectorizerPass(PassRegistry&);

llvm/lib/IR/CMakeLists.txt

@@ -43,6 +43,7 @@ add_llvm_library(LLVMCore
   Pass.cpp
   PassManager.cpp
   PassRegistry.cpp
+  SafepointIRVerifier.cpp
   ProfileSummary.cpp
   Statepoint.cpp
   Type.cpp

llvm/lib/IR/Core.cpp

@@ -50,6 +50,7 @@ void llvm::initializeCore(PassRegistry &Registry) {
   initializePrintModulePassWrapperPass(Registry);
   initializePrintFunctionPassWrapperPass(Registry);
   initializePrintBasicBlockPassPass(Registry);
+  initializeSafepointIRVerifierPass(Registry);
   initializeVerifierLegacyPassPass(Registry);
 }