[PATCH] D76611: [SCCP] Use ranges for predicate info conditions.

[Eli Friedman via Phabricator via llvm-commits]

efriedma accepted this revision.
efriedma added a comment.
This revision is now accepted and ready to land.

LGTM



================
Comment at: llvm/lib/Transforms/Scalar/SCCP.cpp:1299
+      LatticeVal &IV = ValueState[I];
+      if (CopyOf->getType()->isIntegerTy()) {
+        auto NewCR =
----------------
efriedma wrote:
> fhahn wrote:
> > efriedma wrote:
> > > Do we want to try to handle the case where we have a constant expression of integer type?
> > Ah yes, I've change it to use ranges only if either operand is a constant range.
> > 
> > I've added a test with a compare of 2 constant ranges. Currently this just swaps the known values and is not too helpful in that case (f14_constexpr2). 
> > 
> > Also, would it be legal to fold something like `i1 icmp eq (i32 ptrtoint (i32* @B to i32), i32 ptrtoint (i32* @B to i32)` to `true`? If it is, it looks like ConstantExpr currently misses that fold.
> I think the order of the conditions might be backwards? Consider if OriginalVal is a ConstantRange, and CondVal is a Constant.
> 
> -----
> 
> I briefly tried the following, and it seems to fold (just passing it to "opt -S"):
> 
> @B = global i32 0
> @C = global i1 icmp eq (i32 ptrtoint (i32* @B to i32), i32 ptrtoint (i32* @B to i32))
Err, actually, hmm... in general, there's sort a conflict here between Constant and ConstantRange here; in more complicated cases, you could end up accidentally landing on overdefined by merging a Constant and a ConstantRange.

I guess it's unlikely to matter very much in practice; constant expressions are relatively rare.


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https://reviews.llvm.org/D76611