[PATCH] D98967: [Analysis]Add getPointersDiff function to improve compile time.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


================
Comment at: llvm/lib/Analysis/LoopAccessAnalysis.cpp:1158-1159
+
+    OffsetA = OffsetA.sextOrTrunc(IdxWidth);
+    OffsetB = OffsetB.sextOrTrunc(IdxWidth);
+
----------------
lebedev.ri wrote:
> ABataev wrote:
> > lebedev.ri wrote:
> > > 
> > It is used for `Size`
> Err, i should have left this as a comment.
> I think this should mention that while we might have traversed into another address space,
> we still want to keep the original index width.
> Either that, or we need to refresh index width.
Ah, I see, thanks.


================
Comment at: llvm/lib/Analysis/LoopAccessAnalysis.cpp:1167-1172
+    // Check if they are based on the same pointer. That makes the offsets
+    // sufficient.
+    int Val = OffsetDelta.getSExtValue() / Size.getSExtValue();
+    if (Val * Size == OffsetDelta)
+      return Val;
+    return None;
----------------
lebedev.ri wrote:
> ABataev wrote:
> > lebedev.ri wrote:
> > > But this checks that `OffsetDelta` is a multiple of original pointed-to type,
> > > not what the comment says?
> > > 
> > > I suppose this overly restrictive.
> > 1. Yes, the comment is wrong, will fix it.
> > 2. Unfortunately not. Caused by a real example.
> Err, i understand what this checks and that this is for sure currently needed in some cases,
> i'm only saying that perhaps some code could deal with sub-element-misalignment.
I can add a boolean param to the function to control this check


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  https://reviews.llvm.org/D98967/new/

https://reviews.llvm.org/D98967