5 files changed, 124 insertions, 1 deletions
diff --git a/llvm/tools/llvm-reduce/CMakeLists.txt b/llvm/tools/llvm-reduce/CMakeLists.txt
index 7be90bc..c8673b4 100644
--- a/llvm/tools/llvm-reduce/CMakeLists.txt
+++ b/llvm/tools/llvm-reduce/CMakeLists.txt
@@ -39,6 +39,7 @@ add_llvm_tool(llvm-reduce
   deltas/ReduceGlobalValues.cpp
   deltas/ReduceGlobalVarInitializers.cpp
   deltas/ReduceGlobalVars.cpp
+  deltas/ReduceInlineCallSites.cpp
   deltas/ReduceInstructions.cpp
   deltas/ReduceInstructionFlags.cpp
   deltas/ReduceInvokes.cpp
diff --git a/llvm/tools/llvm-reduce/DeltaManager.cpp b/llvm/tools/llvm-reduce/DeltaManager.cpp
index f5c6276..9b13202 100644
--- a/llvm/tools/llvm-reduce/DeltaManager.cpp
+++ b/llvm/tools/llvm-reduce/DeltaManager.cpp
@@ -28,6 +28,7 @@
 #include "deltas/ReduceGlobalVarInitializers.h"
 #include "deltas/ReduceGlobalVars.h"
 #include "deltas/ReduceIRReferences.h"
+#include "deltas/ReduceInlineCallSites.h"
 #include "deltas/ReduceInstructionFlags.h"
 #include "deltas/ReduceInstructionFlagsMIR.h"
 #include "deltas/ReduceInstructions.h"
diff --git a/llvm/tools/llvm-reduce/DeltaPasses.def b/llvm/tools/llvm-reduce/DeltaPasses.def
index 3aed0cc..845b106 100644
--- a/llvm/tools/llvm-reduce/DeltaPasses.def
+++ b/llvm/tools/llvm-reduce/DeltaPasses.def
@@ -58,7 +58,7 @@ DELTA_PASS_IR("volatile", reduceVolatileInstructionsDeltaPass, "Reducing Volatil
 DELTA_PASS_IR("atomic-ordering", reduceAtomicOrderingDeltaPass, "Reducing Atomic Ordering")
 DELTA_PASS_IR("syncscopes", reduceAtomicSyncScopesDeltaPass, "Reducing Atomic Sync Scopes")
 DELTA_PASS_IR("instruction-flags", reduceInstructionFlagsDeltaPass, "Reducing Instruction Flags")
-
+DELTA_PASS_IR("inline-call-sites", reduceInlineCallSitesDeltaPass, "Inlining callsites")
 
 #ifndef DELTA_PASS_MIR
 #define DELTA_PASS_MIR(NAME, FUNC, DESC)
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.cpp b/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.cpp
new file mode 100644
index 0000000..cfef367
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.cpp
@@ -0,0 +1,103 @@
+//===- ReduceInlineCallSites.cpp ------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceInlineCallSites.h"
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+
+using namespace llvm;
+
+extern cl::OptionCategory LLVMReduceOptions;
+
+static cl::opt<int> CallsiteInlineThreshold(
+    "reduce-callsite-inline-threshold",
+    cl::desc("Number of instructions in a function to unconditionally inline "
+             "(-1 for inline all)"),
+    cl::init(5), cl::cat(LLVMReduceOptions));
+
+static bool functionHasMoreThanNonTerminatorInsts(const Function &F,
+                                                  uint64_t NumInsts) {
+  uint64_t InstCount = 0;
+  for (const BasicBlock &BB : F) {
+    for (const Instruction &I : make_range(BB.begin(), std::prev(BB.end()))) {
+      (void)I;
+      if (InstCount++ > NumInsts)
+        return true;
+    }
+  }
+
+  return false;
+}
+
+static bool hasOnlyOneCallUse(const Function &F) {
+  unsigned UseCount = 0;
+  for (const Use &U : F.uses()) {
+    const CallBase *CB = dyn_cast<CallBase>(U.getUser());
+    if (!CB || !CB->isCallee(&U))
+      return false;
+    if (UseCount++ > 1)
+      return false;
+  }
+
+  return UseCount == 1;
+}
+
+// TODO: This could use more thought.
+static bool inlineWillReduceComplexity(const Function &Caller,
+                                       const Function &Callee) {
+  // Backdoor to force all possible inlining.
+  if (CallsiteInlineThreshold < 0)
+    return true;
+
+  if (!hasOnlyOneCallUse(Callee))
+    return false;
+
+  // Permit inlining small functions into big functions, or big functions into
+  // small functions.
+  if (!functionHasMoreThanNonTerminatorInsts(Callee, CallsiteInlineThreshold) &&
+      !functionHasMoreThanNonTerminatorInsts(Caller, CallsiteInlineThreshold))
+    return true;
+
+  return false;
+}
+
+static void reduceCallSites(Oracle &O, Function &F) {
+  std::vector<std::pair<CallBase *, InlineFunctionInfo>> CallSitesToInline;
+
+  for (Use &U : F.uses()) {
+    if (CallBase *CB = dyn_cast<CallBase>(U.getUser())) {
+      // Ignore callsites with wrong call type.
+      if (!CB->isCallee(&U))
+        continue;
+
+      // We do not consider isInlineViable here. It is overly conservative in
+      // cases that the inliner should handle correctly (e.g. disallowing inline
+      // of of functions with indirectbr). Some of the other cases are for other
+      // correctness issues which we do need to worry about here.
+
+      // TODO: Should we delete the function body?
+      InlineFunctionInfo IFI;
+      if (CanInlineCallSite(*CB, IFI).isSuccess() &&
+          inlineWillReduceComplexity(*CB->getFunction(), F) && !O.shouldKeep())
+        CallSitesToInline.emplace_back(CB, std::move(IFI));
+    }
+  }
+
+  // TODO: InlineFunctionImpl will implicitly perform some simplifications /
+  // optimizations which we should be able to opt-out of.
+  for (auto [CB, IFI] : CallSitesToInline)
+    InlineFunctionImpl(*CB, IFI);
+}
+
+void llvm::reduceInlineCallSitesDeltaPass(Oracle &O, ReducerWorkItem &Program) {
+  for (Function &F : Program.getModule()) {
+    if (!F.isDeclaration())
+      reduceCallSites(O, F);
+  }
+}
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.h b/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.h
new file mode 100644
index 0000000..1df31a1
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceInlineCallSites.h
@@ -0,0 +1,18 @@
+//===- ReduceInlineCallSites.h ----------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEINLINECALLSITES_H
+#define LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEINLINECALLSITES_H
+
+#include "Delta.h"
+
+namespace llvm {
+void reduceInlineCallSitesDeltaPass(Oracle &O, ReducerWorkItem &Program);
+} // namespace llvm
+
+#endif