stage2: improve handling of 0 bit types

 * Sema: zirAtomicLoad handles 0-bit types correctly
 * LLVM backend: when lowering function types, elide parameters
   with 0-bit types.
 * Type: abiSize handles u0/i0 correctly

3 files changed, 16 insertions, 7 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index f53dbea90c..990aa4ddf0 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -7803,6 +7803,10 @@ fn zirAtomicLoad(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) Compile
         else => {},
     }
 
+    if (try sema.typeHasOnePossibleValue(block, elem_ty_src, elem_ty)) |val| {
+        return sema.addConstant(elem_ty, val);
+    }
+
     if (try sema.resolveDefinedValue(block, ptr_src, ptr)) |ptr_val| {
         if (try ptr_val.pointerDeref(sema.arena)) |elem_val| {
             return sema.addConstant(elem_ty, elem_val);
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 2e835260af..2f703e2d68 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -541,17 +541,21 @@ pub const DeclGen = struct {
         defer self.gpa.free(fn_param_types);
         zig_fn_type.fnParamTypes(fn_param_types);
 
-        const llvm_param = try self.gpa.alloc(*const llvm.Type, fn_param_len);
-        defer self.gpa.free(llvm_param);
-
-        for (fn_param_types) |fn_param, i| {
-            llvm_param[i] = try self.llvmType(fn_param);
+        const llvm_param_buffer = try self.gpa.alloc(*const llvm.Type, fn_param_len);
+        defer self.gpa.free(llvm_param_buffer);
+
+        var llvm_params_len: c_uint = 0;
+        for (fn_param_types) |fn_param| {
+            if (fn_param.hasCodeGenBits()) {
+                llvm_param_buffer[llvm_params_len] = try self.llvmType(fn_param);
+                llvm_params_len += 1;
+            }
         }
 
         const fn_type = llvm.functionType(
             try self.llvmType(return_type),
-            llvm_param.ptr,
-            @intCast(c_uint, fn_param_len),
+            llvm_param_buffer.ptr,
+            llvm_params_len,
             .False,
         );
         const llvm_fn = self.llvmModule().addFunction(decl.name, fn_type);
diff --git a/src/type.zig b/src/type.zig
index 122faefbc7..c2dc150347 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -1822,6 +1822,7 @@ pub const Type = extern union {
 
             .int_signed, .int_unsigned => {
                 const bits: u16 = self.cast(Payload.Bits).?.data;
+                if (bits == 0) return 0;
                 return std.math.ceilPowerOfTwoPromote(u16, (bits + 7) / 8);
             },