Add simplification of floating point comparisons with the result
of a select instruction, the same as already exists for integer
comparisons.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118379 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 1955802..66452a5 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -350,6 +350,26 @@
}
}
+ // If the comparison is with the result of a select instruction, check whether
+ // comparing with either branch of the select always yields the same value.
+ if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) {
+ // Make sure the select is on the LHS.
+ if (!isa<SelectInst>(LHS)) {
+ std::swap(LHS, RHS);
+ Pred = CmpInst::getSwappedPredicate(Pred);
+ }
+ SelectInst *SI = cast<SelectInst>(LHS);
+ // Now that we have "fcmp select(cond, TV, FV), RHS", analyse it.
+ // Does "fcmp TV, RHS" simplify?
+ if (Value *TCmp = SimplifyFCmpInst(Pred, SI->getTrueValue(), RHS, TD))
+ // It does! Does "fcmp FV, RHS" simplify?
+ if (Value *FCmp = SimplifyFCmpInst(Pred, SI->getFalseValue(), RHS, TD))
+ // It does! If they simplified to the same value, then use it as the
+ // result of the original comparison.
+ if (TCmp == FCmp)
+ return TCmp;
+ }
+
return 0;
}