[llvm-commits] [llvm] r103007 - in /llvm/trunk: lib/VMCore/Metadata.cpp test/Transforms/GlobalOpt/metadata.ll

[Devang Patel]

Duncan,

llvm.dbg.value is never used to track global variables' value. You may want to add a verifier check. Global values are tracked using named metadata. For example,

@global = internal global i8** null, align 8      ; <i8***> [#uses=1]
!llvm.dbg.gv = !{!0}

!0 = metadata !{i32 524340, i32 0, metadata !1, metadata !"global", metadata !"global", metadata !"", metadata !1, i32 2, metadata !3, i1 true, i1 true, i8*** @global} ; [ DW_TAG_variable ]

-
Devang

On May 4, 2010, at 5:43 AM, Duncan Sands wrote:

> Author: baldrick
> Date: Tue May  4 07:43:36 2010
> New Revision: 103007
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=103007&view=rev
> Log:
> Fix a variant of PR6112 found by thinking about it: when doing
> RAUW of a global variable with a local variable in function F,
> if function local metadata M in function G was using the global
> then M would become function-local to both F and G, which is not
> allowed.  See the testcase for an example.  Fixed by detecting
> this situation and zapping the metadata operand when it occurs.
> 
> Modified:
>    llvm/trunk/lib/VMCore/Metadata.cpp
>    llvm/trunk/test/Transforms/GlobalOpt/metadata.ll
> 
> Modified: llvm/trunk/lib/VMCore/Metadata.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Metadata.cpp?rev=103007&r1=103006&r2=103007&view=diff
> ==============================================================================
> --- llvm/trunk/lib/VMCore/Metadata.cpp (original)
> +++ llvm/trunk/lib/VMCore/Metadata.cpp Tue May  4 07:43:36 2010
> @@ -115,14 +115,17 @@
> }
> 
> static const Function *getFunctionForValue(Value *V) {
> -  assert(!isa<MDNode>(V) && "does not iterate over metadata operands");
>   if (!V) return NULL;
> -  if (Instruction *I = dyn_cast<Instruction>(V))
> -    return I->getParent()->getParent();
> -  if (BasicBlock *BB = dyn_cast<BasicBlock>(V))
> -    return BB->getParent();
> +  if (Instruction *I = dyn_cast<Instruction>(V)) {
> +    BasicBlock *BB = I->getParent();
> +    return BB ? BB->getParent() : 0;
> +  }
>   if (Argument *A = dyn_cast<Argument>(V))
>     return A->getParent();
> +  if (BasicBlock *BB = dyn_cast<BasicBlock>(V))
> +    return BB->getParent();
> +  if (MDNode *MD = dyn_cast<MDNode>(V))
> +    return MD->getFunction();
>   return NULL;
> }
> 
> @@ -272,8 +275,19 @@
>   // with an instruction or some other function-local object.  If this is a
>   // non-function-local MDNode, it can't point to a function-local object.
>   // Handle this case by implicitly dropping the MDNode reference to null.
> -  if (!isFunctionLocal() && To && isFunctionLocalValue(To))
> -    To = 0;
> +  // Likewise if the MDNode is function-local but for a different function.
> +  if (To && isFunctionLocalValue(To)) {
> +    if (!isFunctionLocal())
> +      To = 0;
> +    else {
> +      const Function *F = getFunction();
> +      const Function *FV = getFunctionForValue(To);
> +      // Metadata can be function-local without having an associated function.
> +      // So only consider functions to have changed if non-null.
> +      if (F && FV && F != FV)
> +        To = 0;
> +    }
> +  }
> 
>   if (From == To)
>     return;
> 
> Modified: llvm/trunk/test/Transforms/GlobalOpt/metadata.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalOpt/metadata.ll?rev=103007&r1=103006&r2=103007&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/GlobalOpt/metadata.ll (original)
> +++ llvm/trunk/test/Transforms/GlobalOpt/metadata.ll Tue May  4 07:43:36 2010
> @@ -1,7 +1,8 @@
> ; RUN: opt -S -globalopt < %s | FileCheck %s
> 
> ; PR6112 - When globalopt does RAUW(@G, %G), the metadata reference should drop
> -; to null.
> +; to null.  Function local metadata that references @G from a different function
> +; to that containing %G should likewise drop to null.
> @G = internal global i8** null
> 
> define i32 @main(i32 %argc, i8** %argv) {
> @@ -11,9 +12,16 @@
>   ret i32 0
> }
> 
> -!named = !{!0}
> +define void @foo(i32 %x) {
> +  call void @llvm.dbg.value(metadata !{i8*** @G, i32 %x}, i64 0, metadata !1)
> +; CHECK: call void @llvm.dbg.value(metadata !{null, i32 %x}, i64 0, metadata !1)
> +  ret void
> +}
> 
> -; CHECK: !0 = metadata !{null}
> -!0 = metadata !{i8*** @G}
> +declare void @llvm.dbg.value(metadata, i64, metadata) nounwind readnone
> 
> +!named = !{!0}
> 
> +!0 = metadata !{i8*** @G}
> +; CHECK: !0 = metadata !{null}
> +!1 = metadata !{i8* null}
> 
> 
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