Move getIndexExpressionsFromGEP() to ScopHelper. NFC.

This function is used by both ScopInfo and ScopBuilder. A common
location for this function is required when ScopInfo and ScopBuilder are
separated into separate files in the next commit.

llvm-svn: 273981

1 files changed, 49 insertions, 0 deletions

diff --git a/polly/lib/Support/ScopHelper.cpp b/polly/lib/Support/ScopHelper.cpp
index c97eedffcf1..9e94b9f5740 100644
--- a/polly/lib/Support/ScopHelper.cpp
+++ b/polly/lib/Support/ScopHelper.cpp
@@ -490,3 +490,52 @@ llvm::BasicBlock *polly::getUseBlock(llvm::Use &U) {
 
   return UI->getParent();
 }
+
+std::tuple<std::vector<const SCEV *>, std::vector<int>>
+polly::getIndexExpressionsFromGEP(GetElementPtrInst *GEP, ScalarEvolution &SE) {
+  std::vector<const SCEV *> Subscripts;
+  std::vector<int> Sizes;
+
+  Type *Ty = GEP->getPointerOperandType();
+
+  bool DroppedFirstDim = false;
+
+  for (unsigned i = 1; i < GEP->getNumOperands(); i++) {
+
+    const SCEV *Expr = SE.getSCEV(GEP->getOperand(i));
+
+    if (i == 1) {
+      if (auto *PtrTy = dyn_cast<PointerType>(Ty)) {
+        Ty = PtrTy->getElementType();
+      } else if (auto *ArrayTy = dyn_cast<ArrayType>(Ty)) {
+        Ty = ArrayTy->getElementType();
+      } else {
+        Subscripts.clear();
+        Sizes.clear();
+        break;
+      }
+      if (auto *Const = dyn_cast<SCEVConstant>(Expr))
+        if (Const->getValue()->isZero()) {
+          DroppedFirstDim = true;
+          continue;
+        }
+      Subscripts.push_back(Expr);
+      continue;
+    }
+
+    auto *ArrayTy = dyn_cast<ArrayType>(Ty);
+    if (!ArrayTy) {
+      Subscripts.clear();
+      Sizes.clear();
+      break;
+    }
+
+    Subscripts.push_back(Expr);
+    if (!(DroppedFirstDim && i == 2))
+      Sizes.push_back(ArrayTy->getNumElements());
+
+    Ty = ArrayTy->getElementType();
+  }
+
+  return std::make_tuple(Subscripts, Sizes);
+}