[llvm] Extend MemoryEffects to Support Target-Specific Memory Locations (PR #148650)

[Paul Walker via llvm-commits]

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@@ -374,7 +375,19 @@ void CodeGenIntrinsic::setProperty(const Record *R) {
     ME &= MemoryEffects::argMemOnly();
   else if (R->getName() == "IntrInaccessibleMemOnly")
     ME &= MemoryEffects::inaccessibleMemOnly();
-  else if (R->getName() == "IntrInaccessibleMemOrArgMemOnly")
+  else if (R->isSubClassOf("IntrInaccessibleReadMemOnly")) {
+    llvm::IRMemLocation Loc = getValueAsIRMemLocation(R, "Loc");
+    if (ME.onlyAccessTargetMemoryLocation())
+      ME = ME.getWithModRef(Loc, ModRefInfo::Ref);
+    else
+      ME &= MemoryEffects::inaccessibleReadMemOnly(Loc);
----------------
paulwalker-arm wrote:

We shouldn't need to overrate `ME` like this. The tablegen classes look like a legacy from before MemortEffects existed and now that we're growing their number I think it would be better for the tablegen to have explicit classes to set them.

Specifically, instead of IntrInaccessibleReadMemOnly/IntrInaccessibleWriteMemOnly can you add IntrRead/IntrWrite classes that take a list of IntrinsicMemoryLocation. Then here you can build up a Read or Write mask. Something like:
```
MemoryEffects ReadMask = MemoryEffects::writeOnly();
for (const Record *Loc : R->getValueAsListOfDefs("Locations"))
  ReadMask = ReadMask.getWithModRef(getValueAsIRMemLocation(Loc), ModRefInfo::ModRef);
ME &= ReadMask;
```
This will align better with the existing properties where you can combine `IntrReadMem` with `IntrRead<[TargetMem1]>` for an intrinsic that only reads `TargetMem1` and does not read or write anything else.

Not relevant to this PR but I think once we have this we can replace many of the existing memory related intrinsic properties because IntrRead/IntrWrite can represent everything.

https://github.com/llvm/llvm-project/pull/148650