Re-apply r269081 and r269082 with a fix for MSVC.

llvm-svn: 269094

1 files changed, 82 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/BitSetUtils.cpp b/llvm/lib/Analysis/BitSetUtils.cpp
new file mode 100644
index 0000000..d83dca6
--- /dev/null
+++ b/llvm/lib/Analysis/BitSetUtils.cpp
@@ -0,0 +1,82 @@
+//===- BitSetUtils.cpp - Utilities related to pointer bitsets -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains functions that make it easier to manipulate bitsets for
+// devirtualization.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BitSetUtils.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+
+using namespace llvm;
+
+// Search for virtual calls that call FPtr and add them to DevirtCalls.
+static void
+findCallsAtConstantOffset(SmallVectorImpl<DevirtCallSite> &DevirtCalls,
+                          Value *FPtr, uint64_t Offset) {
+  for (const Use &U : FPtr->uses()) {
+    Value *User = U.getUser();
+    if (isa<BitCastInst>(User)) {
+      findCallsAtConstantOffset(DevirtCalls, User, Offset);
+    } else if (auto CI = dyn_cast<CallInst>(User)) {
+      DevirtCalls.push_back({Offset, CI});
+    } else if (auto II = dyn_cast<InvokeInst>(User)) {
+      DevirtCalls.push_back({Offset, II});
+    }
+  }
+}
+
+// Search for virtual calls that load from VPtr and add them to DevirtCalls.
+static void
+findLoadCallsAtConstantOffset(Module *M,
+                              SmallVectorImpl<DevirtCallSite> &DevirtCalls,
+                              Value *VPtr, uint64_t Offset) {
+  for (const Use &U : VPtr->uses()) {
+    Value *User = U.getUser();
+    if (isa<BitCastInst>(User)) {
+      findLoadCallsAtConstantOffset(M, DevirtCalls, User, Offset);
+    } else if (isa<LoadInst>(User)) {
+      findCallsAtConstantOffset(DevirtCalls, User, Offset);
+    } else if (auto GEP = dyn_cast<GetElementPtrInst>(User)) {
+      // Take into account the GEP offset.
+      if (VPtr == GEP->getPointerOperand() && GEP->hasAllConstantIndices()) {
+        SmallVector<Value *, 8> Indices(GEP->op_begin() + 1, GEP->op_end());
+        uint64_t GEPOffset = M->getDataLayout().getIndexedOffsetInType(
+            GEP->getSourceElementType(), Indices);
+        findLoadCallsAtConstantOffset(M, DevirtCalls, User, Offset + GEPOffset);
+      }
+    }
+  }
+}
+
+void llvm::findDevirtualizableCalls(
+    SmallVectorImpl<DevirtCallSite> &DevirtCalls,
+    SmallVectorImpl<CallInst *> &Assumes, CallInst *CI) {
+  assert(CI->getCalledFunction()->getIntrinsicID() == Intrinsic::bitset_test);
+
+  Module *M = CI->getParent()->getParent()->getParent();
+
+  // Find llvm.assume intrinsics for this llvm.bitset.test call.
+  for (const Use &CIU : CI->uses()) {
+    auto AssumeCI = dyn_cast<CallInst>(CIU.getUser());
+    if (AssumeCI) {
+      Function *F = AssumeCI->getCalledFunction();
+      if (F && F->getIntrinsicID() == Intrinsic::assume)
+        Assumes.push_back(AssumeCI);
+    }
+  }
+
+  // If we found any, search for virtual calls based on %p and add them to
+  // DevirtCalls.
+  if (!Assumes.empty())
+    findLoadCallsAtConstantOffset(M, DevirtCalls,
+                                  CI->getArgOperand(0)->stripPointerCasts(), 0);
+}