[PATCH] D64869: [SCEV] get more accurate range for AddExpr with NW flag

[Philip Reames via Phabricator via llvm-commits]

reames requested changes to this revision.
reames added inline comments.
This revision now requires changes to proceed.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:5568
   if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
-    ConstantRange X = getRangeRef(Add->getOperand(0), SignHint);
-    for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
-      X = X.add(getRangeRef(Add->getOperand(i), SignHint));
+    ConstantRange X(BitWidth, /*isFullSet=*/true);
+    if (maskFlags(Add->getNoWrapFlags(), SCEV::FlagNSW) == SCEV::FlagNSW) {
----------------
Stylistically, it would be much cleaner to add a function to ConstantRange with the signature
CR add(CR, NoWrapKind)


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:5570
+    if (maskFlags(Add->getNoWrapFlags(), SCEV::FlagNSW) == SCEV::FlagNSW) {
+      if (auto *C = dyn_cast<SCEVConstant>(Add->getOperand(0))) {
+        X = getRangeRef(Add->getOperand(1), SignHint);
----------------
Your code is incorrect as implemented.  There's no requirement that a SCEVAddExpr have only two operands.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64869/new/

https://reviews.llvm.org/D64869