[llvm] [InstCombine] Create a class to lazily track computed known bits (PR #66611)

[Nikita Popov via llvm-commits]

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@@ -6256,10 +6252,11 @@ static OverflowResult mapOverflowResult(ConstantRange::OverflowResult OR) {
 
 /// Combine constant ranges from computeConstantRange() and computeKnownBits().
 static ConstantRange
-computeConstantRangeIncludingKnownBits(const Value *V, bool ForSigned,
+computeConstantRangeIncludingKnownBits(const WithCache<const Value *> &V,
+                                       bool ForSigned,
                                        const SimplifyQuery &SQ) {
-  KnownBits Known = ::computeKnownBits(V, /*Depth=*/0, SQ);
-  ConstantRange CR1 = ConstantRange::fromKnownBits(Known, ForSigned);
+  ConstantRange CR1 =
+      ConstantRange::fromKnownBits(V.getKnownBits(SQ), ForSigned);
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nikic wrote:

If we add a getConstantRange API on this class, then what it would have to return is a cached version of computeConstantRange(), not ConstantRange::fromKnownBits(). That's something we could evaluate, but not as part of this PR. I don't think it would be worthwhile right now.

https://github.com/llvm/llvm-project/pull/66611