[llvm-reduce] add ReduceAttribute delta pass

[nickdesaulniers]

Summary

The output from llvm-reduce still has significantly more attributes than
bugpoint does. Teach llvm-reduce to remove attributes.

[george.burgess.iv]

Thanks for this! I'm always happy to see reduction tooling gain new powers :)

I've only touched these files in passing, so I'm probably not the best person to LGTM stamp. Just a few tiny nits.

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

2

nit: ReduceAttributes.cpp

33

nit: looks like const std::vector<T> & would match the std::function signature in runDeltaPass, and save us a copy?

35

nit: indices are generally unsigned

49

nit: int, since this function is returning an int?

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

2

nit: ReduceAttributes.h

[nickdesaulniers]

llvm/test/Reduce/Inputs/remove-attributes.py

6

yikes! indentation

[nickdesaulniers]

• fix indentation, signedness, block comments

[nickdesaulniers]

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

35

The comparison below against ChunksToKeep[ChunkIndex].end would be against an int. If I change AttributesIndex to unsigned, I get the following warning:

../tools/llvm-reduce/deltas/ReduceAttributes.cpp:41:26: warning: comparison of integers of different signs: 'unsigned int' and 'int' [-Wsign-compare]
      if (AttributeIndex == ChunksToKeep[ChunkIndex].end)
          ~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

since Chunk::end is an int. (Though I don't think it makes sense for chunks to ever be negative. I could change the Chunk interface if it's not a yak shave, if you'd like?)

[george.burgess.iv]

LGTM after this last nit is addressed. Like said, I plan to leave the final stamp to someone with more context. Thanks again!

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

2

.cpp :)

35

Ick. Yeah, if you want to fix the API, feel free, but I'm happy with this as-is until that happens.

[dblaikie]

Looks reasonable to me.

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

53

Maybe include a matching TODO in extractAttributes?

[nickdesaulniers]

• update final nits

[MaskRay]

llvm/test/Reduce/remove-attributes.ll

3

rm -rf frightens me.

rm -f is sufficient.

Mac is failing.. http://45.33.8.238/mac/7303/step_11.txt

5

FileCheck --input-file= or FileCheck <

[nickdesaulniers]

llvm/test/Reduce/remove-attributes.ll

3

Hmmm...I'm not sure why I cannot reproduce.

5

No other tests in this dir do that. It's required?

[lebedev.ri]

This was reverted all the way back in b12176d2aafa0ccb2585aa218fc3b454ba84f2a9.

[lebedev.ri]

@nickdesaulniers are you planning on picking this up?
If not, just so we're done (or are we) with attributes, i can take over?

[nickdesaulniers]

In D73853#2133880, @lebedev.ri wrote:

@nickdesaulniers are you planning on picking this up?
If not, just so we're done (or are we) with attributes, i can take over?

All yours, I didn't/don't have the time to sort out what the issue was on OSX, but if you find/fix/land it, I'll owe you a beer!

[lebedev.ri]

Clean-sheet implementation D83351 landed in rG03640ee0fa73c6eaf8cb12050203027239136789, and bots appear to be happy with it.
Abandon this?

[nickdesaulniers]

Thanks for fixing; I owe you that beer! 🍻

[lebedev.ri]

In D73853#2142749, @nickdesaulniers wrote:

Thanks for fixing; I owe you that beer! 🍻

Not really fixing, i didn't read what this code was doing

llvm/test/Reduce/Inputs/remove-attributes.py

+import sys
+
+for line in open(sys.argv[1], "r"):
+  if "use-soft-float" in line:
+    sys.exit(0) # Interesting!
+
+sys.exit(1)

llvm/test/Reduce/remove-attributes.ll

+; Test that llvm-reduce can remove uninteresting attributes.
+;
+; RUN: rm -rf %t
+; RUN: llvm-reduce --test %python --test-arg %p/Inputs/remove-attributes.py %s -o %t
+; RUN: cat %t | FileCheck  %s
+
+define void @a() #0 {
+  ret void
+}
+define void @b() #1 {
+  ret void
+}
+
+; CHECK: attributes #0 = { "use-soft-float"="false" }
+attributes #0 = { norecurse noreturn nounwind readnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="none" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "patchable-function-entry"="2" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { norecurse }

llvm/tools/llvm-reduce/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   AllTargetsAsmParsers
   AllTargetsCodeGens
   AllTargetsDescs
   AllTargetsInfos
   Core
   IRReader
   Support
   Target
   TransformUtils
   )
 
 add_llvm_tool(llvm-reduce
   llvm-reduce.cpp
   TestRunner.cpp
   deltas/Delta.cpp
-  deltas/ReduceFunctions.cpp
-  deltas/ReduceGlobalVars.cpp
-  deltas/ReduceMetadata.cpp
   deltas/ReduceArguments.cpp
+  deltas/ReduceAttributes.cpp
   deltas/ReduceBasicBlocks.cpp
+  deltas/ReduceFunctions.cpp
+  deltas/ReduceGlobalVars.cpp
   deltas/ReduceInstructions.cpp
+  deltas/ReduceMetadata.cpp
 
   DEPENDS
   intrinsics_gen
   )

llvm/tools/llvm-reduce/DeltaManager.h

 //===- DeltaManager.h - Runs Delta Passes to reduce Input -----------------===//
 //
 // 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 calls each specialized Delta pass in order to reduce the input IR
 // file.
 //
 //===----------------------------------------------------------------------===//
 
 #include "TestRunner.h"
 #include "deltas/Delta.h"
 #include "deltas/ReduceArguments.h"
+#include "deltas/ReduceAttributes.h"
 #include "deltas/ReduceBasicBlocks.h"
 #include "deltas/ReduceFunctions.h"
 #include "deltas/ReduceGlobalVars.h"
-#include "deltas/ReduceMetadata.h"
 #include "deltas/ReduceInstructions.h"
+#include "deltas/ReduceMetadata.h"
 
 namespace llvm {
 
 // TODO: Add CLI option to run only specified Passes (for unit tests)
 inline void runDeltaPasses(TestRunner &Tester) {
   reduceFunctionsDeltaPass(Tester);
   reduceBasicBlocksDeltaPass(Tester);
   reduceGlobalsDeltaPass(Tester);
   reduceMetadataDeltaPass(Tester);
   reduceArgumentsDeltaPass(Tester);
   reduceInstructionsDeltaPass(Tester);
+  reduceAttributesDeltaPass(Tester);
   // TODO: Implement the remaining Delta Passes
 }
 
 } // namespace llvm

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

+//===- ReduceAttributes.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 Attributes in the provided Module.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestRunner.h"
+
+namespace llvm {
+void reduceAttributesDeltaPass(TestRunner &Test);
+} // namespace llvm

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

+//===- ReduceAttributes.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 Attributes in the provided Module.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceAttributes.h"
+
+#include "Delta.h"
+#include "TestRunner.h"
+
+#include "llvm/IR/Attributes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+
+#include <vector>
+
+static void removeAttr(llvm::Function &F, const llvm::Attribute &A) {
+  if (A.isStringAttribute())
+    F.removeFnAttr(A.getKindAsString());
+  else
+    F.removeFnAttr(A.getKindAsEnum());
+}
+
+static void extractAttributes(const std::vector<llvm::Chunk> &ChunksToKeep,
+                              llvm::Module *M) {
+  int AttributeIndex = 0;
+  unsigned ChunkIndex = 0;
+  // TODO: global variables may also have attributes.
+  for (llvm::Function &F : M->getFunctionList()) {
+    for (const llvm::Attribute &A : F.getAttributes().getFnAttributes()) {
+      ++AttributeIndex;
+      if (!ChunksToKeep[ChunkIndex].contains(AttributeIndex))
+        removeAttr(F, A);
+      if (AttributeIndex == ChunksToKeep[ChunkIndex].end)
+        ++ChunkIndex;
+    }
+  }
+}
+
+static int countAttributes(llvm::Module *M) {
+  int TotalAttributeCount = 0;
+  for (const llvm::Function &F : M->getFunctionList())
+    TotalAttributeCount +=
+        F.getAttributes().getFnAttributes().getNumAttributes();
+  // TODO: global variables may also have attributes.
+  return TotalAttributeCount;
+}
+
+void llvm::reduceAttributesDeltaPass(TestRunner &Test) {
+  outs() << "*** Reducing Attributes...\n";
+  int AttributeCount = countAttributes(Test.getProgram());
+  runDeltaPass(Test, AttributeCount, extractAttributes);
+}

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

for (auto &F : *Program)
     for (auto &BB : F)
         InstCount += BB.getInstList().size();
   outs() << "Number of instructions: " << InstCount << "\n";
 
   return InstCount;
 }
 
 void llvm::reduceInstructionsDeltaPass(TestRunner &Test) {
-  outs() << "*** Reducing Insructions...\n";
+  outs() << "*** Reducing Instructions...\n";
   unsigned InstCount = countInstructions(Test.getProgram());
   runDeltaPass(Test, InstCount, extractInstrFromModule);
 }