[Debugify] Strip added metadata in the -debugify-each pipeline

[vsk]

Summary

Share logic to strip debugify metadata between the IR and MIR level
debugify passes. This makes it simpler to hunt for bugs by diffing IR
with vs. without -debugify-each turned on.

As a drive-by, fix an issue causing CallGraphNodes to become invalid
when a dead llvm.dbg.value prototype is deleted.

[dsanders]

LGTM with the behavioural change to StripDebugMachineModule fixed

llvm/include/llvm/IR/IntrinsicInst.h

71 ↗

(On Diff #256692)

I think there might be potential for confusion between isa<DbgInfoIntrinsic>() and DbgInfoIntrinsic::isA(). Maybe isInstForInstrinsic(), or implementsInstrinsic()?

llvm/lib/Transforms/Utils/Debugify.cpp

183–185 ↗

(On Diff #256692)

This will stop StripDebugMachineModule stripping debug info when OnlyDebugified is false.

[vsk]

Address review feedback.

[vsk]

Well, it looks like arcanist ate my patch and spit out a different one. Let me try that again...

[vsk]

Second try to upload patch with arcanist.

[aprantl]

llvm/lib/Transforms/Utils/Debugify.cpp

203 ↗

(On Diff #257040)

I don't think there is, but this could become a helper in MDNode.h

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

static Instruction *tryToMoveFreeBeforeNullTest(CallInst &FI,
   if (!match(FreeInstrBBTerminator, m_UnconditionalBr(SuccBB)))
     return nullptr;
 
   // If there are only 2 instructions in the block, at this point,
   // this is the call to free and unconditional.
   // If there are more than 2 instructions, check that they are noops
   // i.e., they won't hurt the performance of the generated code.
   if (FreeInstrBB->size() != 2) {
-    for (const Instruction &Inst : *FreeInstrBB) {
+    for (const Instruction &Inst : FreeInstrBB->instructionsWithoutDebug()) {
       if (&Inst == &FI || &Inst == FreeInstrBBTerminator)
         continue;
       auto *Cast = dyn_cast<CastInst>(&Inst);
       if (!Cast || !Cast->isNoopCast(DL))
         return nullptr;
     }
   }
   // Validate the rest of constraint #1 by matching on the pred branch.

llvm/test/Transforms/InstCombine/malloc-free-delete-dbginvar.ll

+; Check that the instcombine result is the same with/without debug info.
+; This is a regression test for a function taken from malloc-free-delete.ll.
+
+; RUN: opt < %s -instcombine -S > %t.no_dbg.ll
+; RUN: opt < %s -debugify-each -instcombine -S > %t.ll
+; RUN: diff %t.no_dbg.ll %t.ll
+
+declare void @free(i8*)
+
+define void @test12(i32* %foo) minsize {
+entry:
+  %tobool = icmp eq i32* %foo, null
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %bitcast = bitcast i32* %foo to i8*
+  tail call void @free(i8* %bitcast)
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  ret void
+}