this pass calls simplifyCFG on individual basic blocks; we want this

so that we can reduce away incidental parts of the CFG in cases where
the full simplifyCFG pass makes the test case uninteresting

Differential Revision: https://reviews.llvm.org/D131920

llvm/test/tools/llvm-reduce/simplify-cfg.ll

@@ -0,0 +1,32 @@
+; RUN: llvm-reduce --delta-passes=simplify-cfg --test %python --test-arg %p/Inputs/remove-bbs.py -abort-on-invalid-reduction %s -o %t
+
+; RUN: FileCheck --check-prefix=CHECK-FINAL %s --input-file=%t
+; CHECK-FINAL-NOT: x6
+; CHECK-FINAL-NOT: x10
+
+define void @f1(ptr %interesting3, i32 %interesting2) {
+  %x3 = alloca ptr, i32 0, align 8
+  store ptr %interesting3, ptr %interesting3, align 8
+  switch i32 %interesting2, label %interesting1 [
+    i32 0, label %x6
+    i32 1, label %x11
+  ]
+
+x4:
+  %x5 = call ptr @f2()
+  br label %x10
+
+x10:
+  br label %interesting1
+
+x6:
+  br label %x11
+
+x11:
+  br label %interesting1
+
+interesting1:
+  ret void
+}
+
+declare ptr @f2()

llvm/tools/llvm-reduce/CMakeLists.txt

@@ -49,6 +49,7 @@ add_llvm_tool(llvm-reduce
   deltas/ReduceRegisterMasks.cpp
   deltas/ReduceRegisterDefs.cpp
   deltas/ReduceRegisterUses.cpp
+  deltas/ReduceUsingSimplifyCFG.cpp
   deltas/RunIRPasses.cpp
   deltas/SimplifyInstructions.cpp
   llvm-reduce.cpp

llvm/tools/llvm-reduce/DeltaManager.cpp

@@ -39,6 +39,7 @@
 #include "deltas/ReduceRegisterMasks.h"
 #include "deltas/ReduceRegisterUses.h"
 #include "deltas/ReduceSpecialGlobals.h"
+#include "deltas/ReduceUsingSimplifyCFG.h"
 #include "deltas/ReduceVirtualRegisters.h"
 #include "deltas/RunIRPasses.h"
 #include "deltas/SimplifyInstructions.h"
@@ -75,6 +76,7 @@ static cl::opt<std::string>
     DELTA_PASS("operands-to-args", reduceOperandsToArgsDeltaPass)              \
     DELTA_PASS("operands-skip", reduceOperandsSkipDeltaPass)                   \
     DELTA_PASS("operand-bundles", reduceOperandBundesDeltaPass)                \
+    DELTA_PASS("simplify-cfg", reduceUsingSimplifyCFGDeltaPass)                \
     DELTA_PASS("attributes", reduceAttributesDeltaPass)                        \
     DELTA_PASS("module-data", reduceModuleDataDeltaPass)                       \
   } while (false)

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

@@ -0,0 +1,34 @@
+//===- ReduceUsingSimplifyCFG.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 call SimplifyCFG on individual basic blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceUsingSimplifyCFG.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
+
+using namespace llvm;
+
+static void reduceUsingSimplifyCFG(Oracle &O, Module &Program) {
+  SmallVector<BasicBlock *, 16> ToSimplify;
+  for (auto &F : Program)
+    for (auto &BB : F)
+      if (!O.shouldKeep())
+        ToSimplify.push_back(&BB);
+  TargetTransformInfo TTI(Program.getDataLayout());
+  for (auto *BB : ToSimplify)
+    simplifyCFG(BB, TTI);
+}
+
+void llvm::reduceUsingSimplifyCFGDeltaPass(TestRunner &Test) {
+  outs() << "*** Reducing using SimplifyCFG...\n";
+  runDeltaPass(Test, reduceUsingSimplifyCFG);
+}

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

@@ -0,0 +1,23 @@
+//===- ReduceUsingSimplifyCFG.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 call SimplifyCFG on individual basic blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_REDUCE_DELTAS_SIMPLIFYCFG_H
+#define LLVM_TOOLS_LLVM_REDUCE_DELTAS_SIMPLIFYCFG_H
+
+#include "Delta.h"
+
+namespace llvm {
+void reduceUsingSimplifyCFGDeltaPass(TestRunner &Test);
+} // namespace llvm
+
+#endif