[PATCH] D86364: [ValueTracking] Interpret GEPs as a series of adds multiplied by the related scaling factor

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:1506
+        if (IndexTypeSize.isScalable())
+          AddrKnownBits.resetAll();
+        if (!AddrKnownBits.isUnknown()) {
----------------
@nikic FYI here is where we stop to track the full address but we still compute the trailing zeros.

If we don't do that, we will lose some information compared to the previous implementation.
E.g., test/Analysis/ScalarEvolution/scalable-vector.ll will fail
:5:10: error: CHECK: expected string not found in input
; CHECK: --> (3 * sizeof(<vscale x 4 x i32>)) U: [0,-15) S: [-9223372036854775808,9223372036854775793)
         ^
<stdin>:4:2: note: scanning from here
 --> (3 * sizeof(<vscale x 4 x i32>)) U: full-set S: full-set


Repository:
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  https://reviews.llvm.org/D86364/new/

https://reviews.llvm.org/D86364