[PATCH] D142387: [SCCP] Use range info to prove AddInst has NUW flag.

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/SCCPSolver.cpp:172
+      if (!Op->getType()->isIntegerTy())
+        return ConstantRange::getFull(1);
+      unsigned Bitwidth = Op->getType()->getScalarSizeInBits();
----------------
Why is this needed?


================
Comment at: llvm/lib/Transforms/Utils/SCCPSolver.cpp:182
+        return ConstantRange::getFull(Bitwidth);
+      return R.getConstantRange();
+    };
----------------
There is an SCCPInstVisitor::getConstantRange() helper -- probably that should be moved to SCCPSolver and reused here?


================
Comment at: llvm/lib/Transforms/Utils/SCCPSolver.cpp:188
+    auto NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
+        Instruction::Add, RangeA, OverflowingBinaryOperator::NoUnsignedWrap);
+    if (NUWRange.contains(RangeB)) {
----------------
Should be RangeB. Doesn't make a difference for add, but would be wrong when extending to sub.


Repository:
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  https://reviews.llvm.org/D142387/new/

https://reviews.llvm.org/D142387