stage2: check address space cast validity

1 files changed, 20 insertions, 1 deletions

diff --git a/src/target.zig b/src/target.zig
index b7da04e548..3fbaf6abc4 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const Type = @import("type.zig").Type;
+const AddressSpace = std.builtin.AddressSpace;
 
 pub const ArchOsAbi = struct {
     arch: std.Target.Cpu.Arch,
@@ -635,12 +636,30 @@ pub fn defaultAddressSpace(
         /// Query the default address space for functions themselves.
         function,
     },
-) std.builtin.AddressSpace {
+) AddressSpace {
     _ = target;
     _ = context;
     return .generic;
 }
 
+/// Returns true if pointers in `from` can be converted to a pointer in `to`.
+pub fn addrSpaceCastIsValid(
+    target: std.Target,
+    from: AddressSpace,
+    to: AddressSpace,
+) bool {
+    const arch = target.cpu.arch;
+    switch (arch) {
+        .x86_64, .i386 => return arch.supportsAddressSpace(from) and arch.supportsAddressSpace(to),
+        .amdgcn => {
+            const to_generic = arch.supportsAddressSpace(from) and to == .generic;
+            const from_generic = arch.supportsAddressSpace(to) and from == .generic;
+            return to_generic or from_generic;
+        },
+        else => return from == .generic and to == .generic,
+    }
+}
+
 pub fn llvmMachineAbi(target: std.Target) ?[:0]const u8 {
     const have_float = switch (target.abi) {
         .gnuilp32 => return "ilp32",