[PM/AA] Split the location computation out of getArgLocation so the

virtual interface on AliasAnalysis only deals with ModRef information.

This interface was both computing memory locations by using TLI and
other tricks to estimate the size of memory referenced by an operand,
and computing ModRef information through similar investigations. This
change narrows the scope of the virtual interface on AliasAnalysis
slightly.

Note that all of this code could live in BasicAA, and be done with
a single investigation of the argument, if it weren't for the fact that
the generic code in AliasAnalysis::getModRefBehavior for a callsite
calls into the virtual aspect of (now) getArgModRefInfo. But this
patch's arrangement seems a not terrible way to go for now.

The other interesting wrinkle is how we could reasonably extend LLVM
with support for custom memory location sizes and mod/ref behavior for
library routines. After discussions with Hal on the review, the
conclusion is that this would be best done by fleshing out the much
desired support for extensions to TLI, and support these types of
queries in that interface where we would likely be doing other library
API recognition and analysis.

Differential Revision: http://reviews.llvm.org/D10259

llvm-svn: 239884

1 files changed, 84 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/MemoryLocation.cpp b/llvm/lib/Analysis/MemoryLocation.cpp
index f87a017b921..e4491261e05 100644
--- a/llvm/lib/Analysis/MemoryLocation.cpp
+++ b/llvm/lib/Analysis/MemoryLocation.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/MemoryLocation.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Instructions.h"
@@ -88,3 +89,86 @@ MemoryLocation MemoryLocation::getForDest(const MemIntrinsic *MTI) {
 
   return MemoryLocation(MTI->getRawDest(), Size, AATags);
 }
+
+// FIXME: This code is duplicated with BasicAliasAnalysis and should be hoisted
+// to some common utility location.
+static bool isMemsetPattern16(const Function *MS,
+                              const TargetLibraryInfo &TLI) {
+  if (TLI.has(LibFunc::memset_pattern16) &&
+      MS->getName() == "memset_pattern16") {
+    FunctionType *MemsetType = MS->getFunctionType();
+    if (!MemsetType->isVarArg() && MemsetType->getNumParams() == 3 &&
+        isa<PointerType>(MemsetType->getParamType(0)) &&
+        isa<PointerType>(MemsetType->getParamType(1)) &&
+        isa<IntegerType>(MemsetType->getParamType(2)))
+      return true;
+  }
+
+  return false;
+}
+
+MemoryLocation MemoryLocation::getForArgument(ImmutableCallSite CS,
+                                              unsigned ArgIdx,
+                                              const TargetLibraryInfo &TLI) {
+  AAMDNodes AATags;
+  CS->getAAMetadata(AATags);
+  const Value *Arg = CS.getArgument(ArgIdx);
+
+  // We may be able to produce an exact size for known intrinsics.
+  if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+    const DataLayout &DL = II->getModule()->getDataLayout();
+
+    switch (II->getIntrinsicID()) {
+    default:
+      break;
+    case Intrinsic::memset:
+    case Intrinsic::memcpy:
+    case Intrinsic::memmove:
+      assert((ArgIdx == 0 || ArgIdx == 1) &&
+             "Invalid argument index for memory intrinsic");
+      if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
+        return MemoryLocation(Arg, LenCI->getZExtValue(), AATags);
+      break;
+
+    case Intrinsic::lifetime_start:
+    case Intrinsic::lifetime_end:
+    case Intrinsic::invariant_start:
+      assert(ArgIdx == 1 && "Invalid argument index");
+      return MemoryLocation(
+          Arg, cast<ConstantInt>(II->getArgOperand(0))->getZExtValue(), AATags);
+
+    case Intrinsic::invariant_end:
+      assert(ArgIdx == 2 && "Invalid argument index");
+      return MemoryLocation(
+          Arg, cast<ConstantInt>(II->getArgOperand(1))->getZExtValue(), AATags);
+
+    case Intrinsic::arm_neon_vld1:
+      assert(ArgIdx == 0 && "Invalid argument index");
+      // LLVM's vld1 and vst1 intrinsics currently only support a single
+      // vector register.
+      return MemoryLocation(Arg, DL.getTypeStoreSize(II->getType()), AATags);
+
+    case Intrinsic::arm_neon_vst1:
+      assert(ArgIdx == 0 && "Invalid argument index");
+      return MemoryLocation(
+          Arg, DL.getTypeStoreSize(II->getArgOperand(1)->getType()), AATags);
+    }
+  }
+
+  // We can bound the aliasing properties of memset_pattern16 just as we can
+  // for memcpy/memset.  This is particularly important because the
+  // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
+  // whenever possible.
+  if (CS.getCalledFunction() &&
+      isMemsetPattern16(CS.getCalledFunction(), TLI)) {
+    assert((ArgIdx == 0 || ArgIdx == 1) &&
+           "Invalid argument index for memset_pattern16");
+    if (ArgIdx == 1)
+      return MemoryLocation(Arg, 16, AATags);
+    if (const ConstantInt *LenCI = dyn_cast<ConstantInt>(CS.getArgument(2)))
+      return MemoryLocation(Arg, LenCI->getZExtValue(), AATags);
+  }
+  // FIXME: Handle memset_pattern4 and memset_pattern8 also.
+
+  return MemoryLocation(CS.getArgument(ArgIdx), UnknownSize, AATags);
+}