[PATCH] D17863: Swift Calling Convention: add swiftcc

[Tim Northover via llvm-commits]

t.p.northover added inline comments.

================
Comment at: lib/Target/X86/X86CallingConv.td:196-199
@@ +195,6 @@
+def RetCC_X86_64_Swift : CallingConv<[
+  // For integers, ECX, R8D can be used as extra return registers.
+  CCIfType<[i8] , CCAssignToReg<[AL, DL, CL, R8B]>>,
+  CCIfType<[i16], CCAssignToReg<[AX, DX, CX, R8W]>>,
+  CCIfType<[i32], CCAssignToReg<[EAX, EDX, ECX, R8D]>>,
+  CCIfType<[i64], CCAssignToReg<[RAX, RDX, RCX, R8]>>,
----------------
manmanren wrote:
> Hi Tim,
> 
> i1 type is promoted to i8 before reaching here. That is why we don't need to handle i1 here.
> This is what other RetCCs do, such as RetCC_X86_32_Fast, but I am not against making it explicit here.
Where does it get promoted? To me it looks like RetCC_X86_64 directly calls RetCC_X86_64_Swift, which doesn't handle it. It then gets forwarded to RetCC_X86Common which promotes to i8 and only uses AL, DL, CL.

I suspect you'll find that something like

    define [4 x i1] @foo() {
        %res = insertvalue [4 x i1] undef, i1 true, 3
        ret [4 x i1] %res
    }

does not do what you're expecting.


http://reviews.llvm.org/D17863