diff --git a/lib/compiler/aro_translate_c/ast.zig b/lib/compiler/aro_translate_c/ast.zig
index 4dcae6dcaa..b92db7862f 100644
--- a/lib/compiler/aro_translate_c/ast.zig
+++ b/lib/compiler/aro_translate_c/ast.zig
@@ -560,6 +560,7 @@ pub const Payload = struct {
         pub const CallingConvention = enum {
             c,
             x86_64_sysv,
+            x86_64_win,
             x86_stdcall,
             x86_fastcall,
             x86_thiscall,
@@ -567,6 +568,7 @@ pub const Payload = struct {
             aarch64_vfabi,
             arm_aapcs,
             arm_aapcs_vfp,
+            m68k_rtd,
         };
     };
 
@@ -2834,6 +2836,7 @@ fn renderFunc(c: *Context, node: Node) !NodeIndex {
                 });
             },
             .x86_64_sysv,
+            .x86_64_win,
             .x86_stdcall,
             .x86_fastcall,
             .x86_thiscall,
@@ -2841,6 +2844,7 @@ fn renderFunc(c: *Context, node: Node) !NodeIndex {
             .aarch64_vfabi,
             .arm_aapcs,
             .arm_aapcs_vfp,
+            .m68k_rtd,
             => cc_node: {
                 // .{ .foo = .{} }
                 _ = try c.addToken(.period, ".");
diff --git a/src/Zcu.zig b/src/Zcu.zig
index 3262a22dc8..24f1313a0c 100644
--- a/src/Zcu.zig
+++ b/src/Zcu.zig
@@ -3568,12 +3568,27 @@ pub fn callconvSupported(zcu: *Zcu, cc: std.builtin.CallingConvention) union(enu
                 }
             }
             break :ok switch (cc) {
+                .x86_64_sysv,
+                .x86_64_win,
                 .x86_64_vectorcall,
+                .x86_64_regcall_v3_sysv,
+                .x86_64_regcall_v4_win,
                 .x86_fastcall,
                 .x86_thiscall,
                 .x86_vectorcall,
+                .x86_regcall_v3,
+                .x86_regcall_v4_win,
+                .aarch64_vfabi,
+                .aarch64_vfabi_sve,
+                .arm_aapcs,
+                .arm_aapcs_vfp,
+                .riscv64_lp64_v,
+                .riscv32_ilp32_v,
+                .m68k_rtd,
                 => |opts| opts.incoming_stack_alignment == null,
 
+                .x86_sysv,
+                .x86_win,
                 .x86_stdcall,
                 => |opts| opts.incoming_stack_alignment == null and opts.register_params == 0,
 
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index a93204e033..be8d2ad2a5 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -7605,16 +7605,38 @@ fn writeMemoryOrder(w: anytype, order: std.builtin.AtomicOrder) !void {
 }
 
 fn toCallingConvention(cc: std.builtin.CallingConvention, zcu: *Zcu) ?[]const u8 {
+    if (zcu.getTarget().cCallingConvention()) |ccc| {
+        if (cc.eql(ccc)) {
+            return null;
+        }
+    }
     return switch (cc) {
         .auto, .naked => null,
+
+        .x86_64_sysv, .x86_sysv => "sysv_abi",
+        .x86_64_win, .x86_win => "ms_abi",
         .x86_stdcall => "stdcall",
         .x86_fastcall => "fastcall",
-        .x86_vectorcall, .x86_64_vectorcall => "vectorcall",
-        else => {
-            // `Zcu.callconvSupported` means this must be the C callconv.
-            assert(cc.eql(zcu.getTarget().cCallingConvention().?));
-            return null;
-        },
+        .x86_thiscall => "thiscall",
+
+        .x86_vectorcall,
+        .x86_64_vectorcall,
+        => "vectorcall",
+
+        .x86_64_regcall_v3_sysv,
+        .x86_64_regcall_v4_win,
+        .x86_regcall_v3,
+        .x86_regcall_v4_win,
+        => "regcall",
+
+        .aarch64_vfabi => "aarch64_vector_pcs",
+        .aarch64_vfabi_sve => "aarch64_sve_pcs",
+        .arm_aapcs => "pcs(\"aapcs\")",
+        .arm_aapcs_vfp => "pcs(\"aapcs-vfp\")",
+        .riscv64_lp64_v, .riscv32_ilp32_v => "riscv_vector_cc",
+        .m68k_rtd => "m68k_rtd",
+
+        else => unreachable, // `Zcu.callconvSupported`
     };
 }
 
diff --git a/src/translate_c.zig b/src/translate_c.zig
index 92d3110ff8..a58951c228 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -5005,6 +5005,7 @@ fn transCC(
     return switch (clang_cc) {
         .C => .c,
         .X86_64SysV => .x86_64_sysv,
+        .Win64 => .x86_64_win,
         .X86StdCall => .x86_stdcall,
         .X86FastCall => .x86_fastcall,
         .X86ThisCall => .x86_thiscall,
@@ -5012,6 +5013,7 @@ fn transCC(
         .AArch64VectorCall => .aarch64_vfabi,
         .AAPCS => .arm_aapcs,
         .AAPCS_VFP => .arm_aapcs_vfp,
+        .M68kRTD => .m68k_rtd,
         else => return fail(
             c,
             error.UnsupportedType,