[PATCH] D18841: [InstCombine] Canonicalize icmp instructions based on dominating conditions.

[Sanjoy Das via llvm-commits]

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

This looks okay to me (pending the one inline comment), assuming @majnemer is fine with too.

Btw, looks like instcombine already canonicalizes towards equality, for instance:

  define i1 @f(i32 %x) {
    %v = icmp ugt i32 %x, 0
    ret i1 %v
  }

is instcombined to

  define i1 @f(i32 %x) {
    %v = icmp ne i32 %x, 0
    ret i1 %v
  }

and this change looks like it is doing more of the same.


================
Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:3287
@@ +3286,3 @@
+    auto *BI =
+        Dom ? dyn_cast_or_null<BranchInst>(Dom->getTerminator()) : nullptr;
+    ICmpInst::Predicate Pred;
----------------
I think you can just use `dyn_cast` here.  For a well formed CFG, `getTerminator` should always return `nonnull`.


http://reviews.llvm.org/D18841