[llvm] [ValueTracking] Handle intrinsics in `computeConstantRange` (PR #100870)

[Nikita Popov via llvm-commits]

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@@ -9728,6 +9728,17 @@ ConstantRange llvm::computeConstantRange(const Value *V, bool ForSigned,
     if (const auto *CB = dyn_cast<CallBase>(V))
       if (std::optional<ConstantRange> Range = CB->getRange())
         CR = CR.intersectWith(*Range);
+
+    if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
+      Intrinsic::ID IID = II->getIntrinsicID();
+      if (ConstantRange::isIntrinsicSupported(IID)) {
+        SmallVector<ConstantRange, 2> OpRanges;
+        for (Value *Op : II->args())
+          OpRanges.push_back(computeConstantRange(Op, ForSigned, UseInstrInfo,
+                                                  AC, CtxI, DT, Depth + 1));
+        CR = CR.intersectWith(ConstantRange::intrinsic(IID, OpRanges));
+      }
+    }
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nikic wrote:

Placing the code here makes no sense, there is already getRangeForIntrinsic above.

https://github.com/llvm/llvm-project/pull/100870