AMDGPU: Remove nan tests in class if src is nnan

llvm-svn: 340850
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 1d0cd11..2993f00 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3282,6 +3282,13 @@
       return replaceInstUsesWith(*II, FCmp);
     }
 
+    // fp_class (nnan x), qnan|snan|other -> fp_class (nnan x), other
+    if (((Mask & S_NAN) || (Mask & Q_NAN)) && isKnownNeverNaN(Src0, &TLI)) {
+      II->setArgOperand(1, ConstantInt::get(Src1->getType(),
+                                            Mask & ~(S_NAN | Q_NAN)));
+      return II;
+    }
+
     const ConstantFP *CVal = dyn_cast<ConstantFP>(Src0);
     if (!CVal) {
       if (isa<UndefValue>(Src0))