[llvm] [CodeGen] Make LoadExtActions address-space aware (PR #162407)

[Matt Arsenault via llvm-commits]

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@@ -1472,27 +1472,40 @@ class LLVM_ABI TargetLoweringBase {
   /// Return how this load with extension should be treated: either it is legal,
   /// needs to be promoted to a larger size, needs to be expanded to some other
   /// code sequence, or the target has a custom expander for it.
-  LegalizeAction getLoadExtAction(unsigned ExtType, EVT ValVT,
-                                  EVT MemVT) const {
-    if (ValVT.isExtended() || MemVT.isExtended()) return Expand;
-    unsigned ValI = (unsigned) ValVT.getSimpleVT().SimpleTy;
-    unsigned MemI = (unsigned) MemVT.getSimpleVT().SimpleTy;
+  LegalizeAction getLoadExtAction(unsigned ExtType, EVT ValVT, EVT MemVT,
+                                  unsigned AddrSpace) const {
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arsenm wrote:

Custom has always meant possibly conditionally legal. Custom lowering can report a contextual individual operation as legal, or actually perform the custom expansion. The trouble is the simple "is legal" or "is custom" query cannot answer if that will happen for a particular node.


> Do you have any thoughts on combining getOperationAction(ISD::LOAD... and getLoadExtAction into a unified getLoadAction

Probably should do that too, the split between ext loads and not-ext loads feels arbitrary 

https://github.com/llvm/llvm-project/pull/162407