[llvm] [DataLayout] Introduce DataLayout::getPointerAddressSize(AS) (PR #137412)

[Alexander Richardson via llvm-commits]

================
@@ -401,6 +401,31 @@ TEST(DataLayout, ParsePointerSpec) {
     EXPECT_THAT_EXPECTED(
         DataLayout::parse(Str),
         FailedWithMessage("index size cannot be larger than the pointer size"));
+
+  EXPECT_THAT_EXPECTED(
+      DataLayout::parse("p:64:64:64:48:32"),
+      FailedWithMessage("index size cannot be larger than the address size"));
+
+  // address size
+  for (StringRef Str : {"p:64:32:32:64:", "p0:64:32:32:64:"})
+    EXPECT_THAT_EXPECTED(
+        DataLayout::parse(Str),
+        FailedWithMessage("address size component cannot be empty"));
+
+  // Note: in the future we might allow 0 for address size to indicate pointers
+  // that do not have a meaning full address (e.g. relocatable GC pointers).
----------------
arichardson wrote:

```suggestion
  // that do not have a meaningful address (e.g. relocatable GC pointers).
```

https://github.com/llvm/llvm-project/pull/137412