diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -12112,7 +12112,6 @@
     if (!Ty->isFloatTy() && (!Subtarget->hasGFX90AInsts() || !Ty->isDoubleTy()))
       return AtomicExpansionKind::CmpXChg;
 
-    // TODO: Do have these for flat. Older targets also had them for buffers.
     unsigned AS = RMW->getPointerAddressSpace();
 
     if ((AS == AMDGPUAS::GLOBAL_ADDRESS || AS == AMDGPUAS::FLAT_ADDRESS) &&
@@ -12128,20 +12127,22 @@
         return AtomicExpansionKind::CmpXChg;
 
       if (Subtarget->hasGFX90AInsts()) {
+        if (Ty->isFloatTy() && AS == AMDGPUAS::FLAT_ADDRESS)
+          return AtomicExpansionKind::CmpXChg;
+
         auto SSID = RMW->getSyncScopeID();
         if (SSID == SyncScope::System ||
             SSID == RMW->getContext().getOrInsertSyncScopeID("one-as"))
           return AtomicExpansionKind::CmpXChg;
 
-        return (Ty->isFloatTy() && AS == AMDGPUAS::FLAT_ADDRESS) ?
-          AtomicExpansionKind::CmpXChg : AtomicExpansionKind::None;
+        return AtomicExpansionKind::None;
       }
 
-      if (!Subtarget->hasGFX90AInsts() && AS != AMDGPUAS::GLOBAL_ADDRESS)
+      if (AS == AMDGPUAS::FLAT_ADDRESS)
         return AtomicExpansionKind::CmpXChg;
 
-      return RMW->use_empty() ? AtomicExpansionKind::None :
-                                AtomicExpansionKind::CmpXChg;
+      return RMW->use_empty() ? AtomicExpansionKind::None
+                              : AtomicExpansionKind::CmpXChg;
     }
 
     // DS FP atomics do repect the denormal mode, but the rounding mode is fixed