[PATCH] D21775: [InstCombine] Simplify and correct folding fcmps with the same children

[Tim Shen via llvm-commits]

timshen added inline comments.

================
Comment at: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:1125-1133
@@ +1124,11 @@
+
+  // Simplify (fcmp cc0 x, y) & (fcmp cc1 x, y).
+  // Suppose the relation between x and y is R, where R is one of
+  // U(1000), L(0100), G(0010) or E(0001), and CC0 and CC1 are the bitmasks for
+  // testing the desired relations.
+  //
+  // Since (R & CC0) and (R & CC1) are either R or 0, we actually have this:
+  //    bool(R & CC0) && bool(R & CC1)
+  //  = bool((R & CC0) & (R & CC1))
+  //  = bool(R & (CC0 & CC1)) <= by re-association, commutation, and idempotency
+  if (Op0LHS == Op1LHS && Op0RHS == Op1RHS)
----------------
spatel wrote:
> This comment and the similar one below didn't make anything clearer to me. I would leave it out, but that's just my suggestion.
The boolean logic deduction is quite different though. :)

I removed the first duplicated paragraph in FoldOrOfFCmps.


http://reviews.llvm.org/D21775