add a new pass to instrument loads and stores for run-time bounds checking

move EmitGEPOffset from InstCombine to Transforms/Utils/Local.h

(a draft of this) patch reviewed by Andrew, thanks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157261 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 61 insertions, 0 deletions

diff --git a/include/llvm/Transforms/Utils/Local.h b/include/llvm/Transforms/Utils/Local.h
index 7f99dbc..936d58e 100644
--- a/include/llvm/Transforms/Utils/Local.h
+++ b/include/llvm/Transforms/Utils/Local.h
@@ -15,6 +15,11 @@
 #ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
 #define LLVM_TRANSFORMS_UTILS_LOCAL_H
 
+#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/IRBuilder.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Operator.h"
+
 namespace llvm {
 
 class User;
@@ -160,6 +165,62 @@ static inline unsigned getKnownAlignment(Value *V, const TargetData *TD = 0) {
   return getOrEnforceKnownAlignment(V, 0, TD);
 }
 
+/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
+/// code necessary to compute the offset from the base pointer (without adding
+/// in the base pointer).  Return the result as a signed integer of intptr size.
+template<typename IRBuilderTy>
+Value *EmitGEPOffset(IRBuilderTy *Builder, const TargetData &TD, User *GEP) {
+  gep_type_iterator GTI = gep_type_begin(GEP);
+  Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
+  Value *Result = Constant::getNullValue(IntPtrTy);
+
+  // If the GEP is inbounds, we know that none of the addressing operations will
+  // overflow in an unsigned sense.
+  bool isInBounds = cast<GEPOperator>(GEP)->isInBounds();
+
+  // Build a mask for high order bits.
+  unsigned IntPtrWidth = TD.getPointerSizeInBits();
+  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
+
+  for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
+       ++i, ++GTI) {
+    Value *Op = *i;
+    uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
+    if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
+      if (OpC->isZero()) continue;
+
+      // Handle a struct index, which adds its field offset to the pointer.
+      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+        Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
+
+        if (Size)
+          Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
+                                      GEP->getName()+".offs");
+        continue;
+      }
+
+      Constant *Scale = ConstantInt::get(IntPtrTy, Size);
+      Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
+      Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
+      // Emit an add instruction.
+      Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
+      continue;
+    }
+    // Convert to correct type.
+    if (Op->getType() != IntPtrTy)
+      Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
+    if (Size != 1) {
+      // We'll let instcombine(mul) convert this to a shl if possible.
+      Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
+                              GEP->getName()+".idx", isInBounds /*NUW*/);
+    }
+
+    // Emit an add instruction.
+    Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
+  }
+  return Result;
+}
+
 ///===---------------------------------------------------------------------===//
 ///  Dbg Intrinsic utilities
 ///