[llvm-reduce] Remove dso_local when possible

[swamulism]

Summary

Add a new delta pass to llvm-reduce that removes dso_local when possible

[lebedev.ri]

We are indeed missing reductions of a number of such things, but isn't this a bit too specialized?
I don't know what the solution is (and that is why i didn't touch it), but i'd be hoping for something more generic..

[fhahn]

In D98673#2628149, @lebedev.ri wrote:

We are indeed missing reductions of a number of such things, but isn't this a bit too specialized?
I don't know what the solution is (and that is why i didn't touch it), but i'd be hoping for something more generic..

We should probably also try to reduce the linkage & visibility. Although it is not completely clear what 'reduced'/'simpler' means here. But I guess it might make sense to try to set them to the default values? Is this the direction you meant with 'more generic' or reducing other bits of globals as well?

[lebedev.ri]

In D98673#2628677, @fhahn wrote:

In D98673#2628149, @lebedev.ri wrote:

We are indeed missing reductions of a number of such things, but isn't this a bit too specialized?
I don't know what the solution is (and that is why i didn't touch it), but i'd be hoping for something more generic..

We should probably also try to reduce the linkage & visibility. Although it is not completely clear what 'reduced'/'simpler' means here. But I guess it might make sense to try to set them to the default values? Is this the direction you meant with 'more generic' or reducing other bits of globals as well?

We also miss nuw/nsw/inbounds/exact and likely others.

[arsenm]

In D98673#2628677, @fhahn wrote:

In D98673#2628149, @lebedev.ri wrote:

We are indeed missing reductions of a number of such things, but isn't this a bit too specialized?
I don't know what the solution is (and that is why i didn't touch it), but i'd be hoping for something more generic..

We should probably also try to reduce the linkage & visibility. Although it is not completely clear what 'reduced'/'simpler' means here. But I guess it might make sense to try to set them to the default values? Is this the direction you meant with 'more generic' or reducing other bits of globals as well?

When I'm reducing codegen problems, I tend to make the linkage and visibility stricter since it ends up with fewer machine instructions

[aeubanks]

The only way to remove dso_local is via GlobalValue::setDSOLocal(), I don't think there is some more generic way to do it.

When reducing, we should decide if we want to reduce to dso_local or the default (dso_preemptable), but we shouldn't just leave it be. Either way is fine to me, although I slightly prefer removing it since it makes the printed IR cleaner, even if that's technically less strict.

We also miss nuw/nsw/inbounds/exact and likely others.

We should also do these, but in a future patch.

[aeubanks]

Maybe we could have two llvm-reduce modes, one for adding as many restrictive qualifiers as possible, and one for making clean IR that uses defaults as much as possible. IMO more people would rather see defaults than restrictive qualifiers.

[aeubanks]

Anyway, I think this looks good, we can always easily change the way we reduce in the future.

[fhahn]

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.cpp

1

nit: this needs fixing?

10

can we say more specifically what this reduces? It only reduces some attributes of globals.

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.h

1

nit: fix formatting?

[swamulism]

Add header guard and format docs

[aeubanks]

separately, we should fix up all the headers in llvm-reduce, they're almost all missing include guards

[swamulism]

Conform to clang-tidy standards

[swamulism]

Actually conform to clang-tidy standards

llvm/test/Reduce/remove-dso-local.ll

+; Test that llvm-reduce can remove dso_local.
+;
+; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefix=CHECK-FINAL %s < %t
+
+; CHECK-INTERESTINGNESS: declare
+; CHECK-INTERESTINGNESS-SAME: void @f0
+; CHECK-INTERESTINGNESS-SAME: i32
+; CHECK-INTERESTINGNESS-SAME: i32
+
+; CHECK-FINAL: declare void @f0(i32, i32)
+
+declare dso_local void @f0(i32, i32)
+
+; CHECK-INTERESTINGNESS: declare
+; CHECK-INTERESTINGNESS-SAME: dso_local
+; CHECK-INTERESTINGNESS-SAME: void @f1
+; CHECK-INTERESTINGNESS-SAME: i32
+; CHECK-INTERESTINGNESS-SAME: i32
+
+; CHECK-FINAL: declare dso_local void @f1(i32, i32)
+
+declare dso_local void @f1(i32, i32)
+

llvm/tools/llvm-reduce/CMakeLists.txt

add_llvm_tool(llvm-reduce
   TestRunner.cpp
   deltas/Delta.cpp
   deltas/ReduceAliases.cpp
   deltas/ReduceArguments.cpp
   deltas/ReduceAttributes.cpp
   deltas/ReduceBasicBlocks.cpp
   deltas/ReduceFunctionBodies.cpp
   deltas/ReduceFunctions.cpp
+  deltas/ReduceGlobalValues.cpp
   deltas/ReduceGlobalVarInitializers.cpp
   deltas/ReduceGlobalVars.cpp
   deltas/ReduceInstructions.cpp
   deltas/ReduceMetadata.cpp
   deltas/ReduceOperandBundles.cpp
   deltas/ReduceSpecialGlobals.cpp
   llvm-reduce.cpp
 
   DEPENDS
   intrinsics_gen
   )

llvm/tools/llvm-reduce/DeltaManager.h

 #include "TestRunner.h"
 #include "deltas/Delta.h"
 #include "deltas/ReduceAliases.h"
 #include "deltas/ReduceArguments.h"
 #include "deltas/ReduceAttributes.h"
 #include "deltas/ReduceBasicBlocks.h"
 #include "deltas/ReduceFunctionBodies.h"
 #include "deltas/ReduceFunctions.h"
+#include "deltas/ReduceGlobalValues.h"
 #include "deltas/ReduceGlobalVarInitializers.h"
 #include "deltas/ReduceGlobalVars.h"
 #include "deltas/ReduceInstructions.h"
 #include "deltas/ReduceMetadata.h"
 #include "deltas/ReduceOperandBundles.h"
 #include "deltas/ReduceSpecialGlobals.h"
 
 namespace llvm {
 
 // TODO: Add CLI option to run only specified Passes (for unit tests)
 inline void runDeltaPasses(TestRunner &Tester) {
   reduceSpecialGlobalsDeltaPass(Tester);
   reduceAliasesDeltaPass(Tester);
   reduceFunctionBodiesDeltaPass(Tester);
   reduceFunctionsDeltaPass(Tester);
   reduceBasicBlocksDeltaPass(Tester);
+  reduceGlobalValuesDeltaPass(Tester);
   reduceGlobalsInitializersDeltaPass(Tester);
   reduceGlobalsDeltaPass(Tester);
   reduceMetadataDeltaPass(Tester);
   reduceArgumentsDeltaPass(Tester);
   reduceInstructionsDeltaPass(Tester);
   reduceOperandBundesDeltaPass(Tester);
   reduceAttributesDeltaPass(Tester);
   // TODO: Implement the remaining Delta Passes
 }
 
 } // namespace llvm

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.h

+//===- ReduceGlobalValues.h - Specialized Delta Pass
+//---------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function which calls the Generic Delta pass in order
+// to reduce Global Values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Delta.h"
+
+namespace llvm {
+void reduceGlobalValuesDeltaPass(TestRunner &Test);
+} // namespace llvm

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.cpp

+//===- ReduceGlobalValues.cpp - Specialized Delta Pass
+//----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function which calls the Generic Delta pass in order
+// to reduce Global Values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceGlobalValues.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/GlobalValue.h"
+
+using namespace llvm;
+
+/// Sets dso_local to false for all global values.
+static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
+                                 Module *Program) {
+  Oracle O(ChunksToKeep);
+
+  // remove dso_local from global values
+  for (auto &GV : Program->global_values())
+    if (GV.isDSOLocal() && !O.shouldKeep()) {
+      GV.setDSOLocal(false);
+    }
+}
+
+/// Counts the amount of global values with dso_local and displays their
+/// respective name & index
+static int countGVs(Module *Program) {
+  // TODO: Silence index with --quiet flag
+  outs() << "----------------------------\n";
+  outs() << "GlobalValue Index Reference:\n";
+  int GVCount = 0;
+  for (auto &GV : Program->global_values())
+    if (GV.isDSOLocal())
+      outs() << "\t" << ++GVCount << ": " << GV.getName() << "\n";
+  outs() << "----------------------------\n";
+  return GVCount;
+}
+
+void llvm::reduceGlobalValuesDeltaPass(TestRunner &Test) {
+  outs() << "*** Reducing GlobalValues...\n";
+  int GVCount = countGVs(Test.getProgram());
+  runDeltaPass(Test, GVCount, extractGVsFromModule);
+}

llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn

sources = [
     "TestRunner.cpp",
     "deltas/Delta.cpp",
     "deltas/ReduceAliases.cpp",
     "deltas/ReduceArguments.cpp",
     "deltas/ReduceAttributes.cpp",
     "deltas/ReduceBasicBlocks.cpp",
     "deltas/ReduceFunctionBodies.cpp",
     "deltas/ReduceFunctions.cpp",
+    "deltas/ReduceGlobalValues.cpp",
     "deltas/ReduceGlobalVarInitializers.cpp",
     "deltas/ReduceGlobalVars.cpp",
     "deltas/ReduceInstructions.cpp",
     "deltas/ReduceMetadata.cpp",
     "deltas/ReduceOperandBundles.cpp",
     "deltas/ReduceSpecialGlobals.cpp",
     "llvm-reduce.cpp",
   ]
 }