[CIR][Dialect] Add verification of address space to get_global (#787)

This PR verifies `cir.get_global` has its result type correctly
annotated with address space of the referenced symbol. The documentation
is also updated to clarify this constraint.

`GlobalOp` is the main consideration. It's worth noting that if the
`cir.get_global` op references a function, we also (implicitly) checks
that its result pointer type has no address space attribute.

Author: seven-mile

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -2231,7 +2231,8 @@ def GetGlobalOp : CIR_Op<"get_global",
     The `cir.get_global` operation retrieves the address pointing to a
     named global variable. If the global variable is marked constant, writing
     to the resulting address (such as through a `cir.store` operation) is
-    undefined. Resulting type must always be a `!cir.ptr<...>` type.
+    undefined. Resulting type must always be a `!cir.ptr<...>` type with the
+    same address space as the global variable.
 
     Addresses of thread local globals can only be retrieved if this operation
     is marked `thread_local`, which indicates the address isn't constant.
@@ -2241,6 +2242,9 @@ def GetGlobalOp : CIR_Op<"get_global",
     %x = cir.get_global @foo : !cir.ptr<i32>
     ...
     %y = cir.get_global thread_local @batata : !cir.ptr<i32>
+    ...
+    cir.global external addrspace(offload_global) @gv = #cir.int<0> : !s32i
+    %z = cir.get_global @gv : !cir.ptr<!s32i, addrspace(offload_global)>
     ```
   }];
 

clang/lib/CIR/Dialect/IR/CIRDialect.cpp

@@ -2044,8 +2044,10 @@ GetGlobalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
            << "' does not reference a valid cir.global or cir.func";
 
   mlir::Type symTy;
+  mlir::cir::AddressSpaceAttr symAddrSpace{};
   if (auto g = dyn_cast<GlobalOp>(op)) {
     symTy = g.getSymType();
+    symAddrSpace = g.getAddrSpaceAttr();
     // Verify that for thread local global access, the global needs to
     // be marked with tls bits.
     if (getTls() && !g.getTlsModel())
@@ -2060,6 +2062,14 @@ GetGlobalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
     return emitOpError("result type pointee type '")
            << resultType.getPointee() << "' does not match type " << symTy
            << " of the global @" << getName();
+
+  if (symAddrSpace != resultType.getAddrSpace()) {
+    return emitOpError()
+           << "result type address space does not match the address "
+              "space of the global @"
+           << getName();
+  }
+
   return success();
 }
 

clang/test/CIR/IR/invalid.cir

@@ -1272,3 +1272,16 @@ module {
     }
 }
 
+// -----
+
+!s32i = !cir.int<s, 32>
+
+module {
+  cir.global external addrspace(offload_global) @gv = #cir.int<0> : !s32i
+
+  cir.func @test_get_global() {
+    // expected-error@+1 {{'cir.get_global' op result type address space does not match the address space of the global @gv}}
+    %addr = cir.get_global @gv : !cir.ptr<!s32i>
+    cir.return
+  }
+}