[PATCH] D48853: [SCEV] Add [zs]ext{C, +, x} -> (D + [zs]ext{C-D, +, x})<nuw><nsw> transform

[Michael Zolotukhin via Phabricator via llvm-commits]

mzolotukhin added a comment.

Hi,

Thanks for working on this! From the description the approach looks correct and promising. I glanced through the patch, and it looked good, but if you don't mind I'd like to have another look.

Thanks,
Michael



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Comment at: lib/Analysis/ScalarEvolution.cpp:1566-1568
+static APInt extractConstantWithoutWrapping(ScalarEvolution &SE,
+                                            const SCEVConstant *ConstantTerm,
+                                            const SCEVAddExpr *FullExpr) {
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Could you please also add a description for `FullExpr`? It might be helpful to add even more examples here and describe the intended use (e.g. `ConstantTerm` is `Start` and `FullExpr` is `Step` of an `AddRec` expression).


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Comment at: lib/Analysis/ScalarEvolution.cpp:1585-1588
+  for (unsigned I = 1, E = FullExpr->getNumOperands(); I < E && TZ; ++I)
+    TZ = std::min(TZ, SE.GetMinTrailingZeros(FullExpr->getOperand(I)));
+  if (TZ)
+    return TZ < BitWidth ? C.trunc(TZ).zext(BitWidth) : C;
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Just checking my understanding: we're basically finding the largest common denominator here, which is also a power of 2, right?


Repository:
  rL LLVM

https://reviews.llvm.org/D48853