[llvm] [AMDGPU] Handle negated f16 and fp conversion DAG combines (PR #213202)

[Matt Arsenault via llvm-commits]

================
@@ -788,6 +790,21 @@ bool AMDGPUTargetLowering::allUsesHaveSourceMods(const SDNode *N,
 
   // XXX - Should this limit number of uses to check?
   for (const SDNode *U : N->users()) {
+    if(U->getOpcode() == ISD::BITCAST && N->getOpcode() == ISD::FP_TO_FP16) {
+      for(const SDNode *BU : U->users()) {
----------------
arsenm wrote:

It's probably a bad idea to scan over all users, and then further scan all users of a user. Is this part really necessary? 

https://github.com/llvm/llvm-project/pull/213202