[llvm_stats] Do not import llvm.stats metadata for thinlto

[wlei]

Summary

The stats are computed per module and will all be merged in the binary, importing the metadata will cause duplication of the stats.

[hoy]

llvm/include/llvm/IR/Metadata.h

60 ↗

(On Diff #478275)

I'm not sure this is a good place to define the constant and I don't see any other good place for it either. Maybe just leave "llvm.stats" in place? "llvm.dbg.cu" is an example.

[wlei]

llvm/include/llvm/IR/Metadata.h

60 ↗

(On Diff #478275)

Sounds good!

[wlei]

Updating D138833: [llvm_stats] Do not import llvm.stats metadata for thinlto

[hoy]

lgtm, thanks.

[wenlei]

thanks for the fix!

llvm/lib/Linker/IRMover.cpp

if (IsPerformingImport && NMD.getName() == PseudoProbeDescMetadataName) {
       if (!DstM.getNamedMetadata(NMD.getName()))
         emitWarning("Pseudo-probe ignored: source module '" +
                     SrcM->getModuleIdentifier() +
                     "' is compiled with -fpseudo-probe-for-profiling while "
                     "destination module '" +
                     DstM.getModuleIdentifier() + "' is not\n");
       continue;
     }
+    // The stats are computed per module and will all be merged in the binary.
+    // Importing the metadata will cause duplication of the stats.
+    if (IsPerformingImport && NMD.getName() == "llvm.stats")
+      continue;
+
     NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
     // Add Src elements into Dest node.
     for (const MDNode *Op : NMD.operands())
       DestNMD->addOperand(Mapper.mapMDNode(*Op));
   }
 }
 
 /// Merge the linker flags in Src into the Dest module.

llvm/test/ThinLTO/X86/Inputs/llvm-stats-import.ll

+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo() {
+entry:
+  ret void
+}
+
+attributes #0 = { inaccessiblememonly nounwind willreturn }
+
+!llvm.stats = !{!0}
+!0 = !{!"foo", i64 456}

llvm/test/ThinLTO/X86/llvm-stats-import.ll

+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %p/Inputs/llvm-stats-import.ll -o %t2.bc
+; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t1.bc %t2.bc
+
+; RUN: llvm-lto -thinlto-action=import %t1.bc -thinlto-index=%t.index.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-MAIN
+; RUN: llvm-lto -thinlto-action=import %t2.bc -thinlto-index=%t.index.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-FOO
+
+; CHECK-MAIN: !0 = !{!"main", i64 123}
+; CHECK-MAIN-NOT: !{!"foo", i64 456}
+
+; CHECK-FOO: !0 = !{!"foo", i64 456}
+; CHECK-FOO-NOT: !{!"main", i64 123}
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @main() {
+entry:
+  call void (...) @foo()
+  ret i32 0
+}
+
+declare void @foo(...)
+
+attributes #0 = { inaccessiblememonly nounwind willreturn }
+
+!llvm.stats = !{!0}
+!0 = !{!"main", i64 123}