3 files changed, 5 insertions, 1 deletions
diff --git a/src/ortho/mcode/ortho_code-x86-abi.adb b/src/ortho/mcode/ortho_code-x86-abi.adb
index 8c746c18a..389e2bdc5 100644
--- a/src/ortho/mcode/ortho_code-x86-abi.adb
+++ b/src/ortho/mcode/ortho_code-x86-abi.adb
@@ -79,8 +79,10 @@ package body Ortho_Code.X86.Abi is
                raise Program_Error;
          end case;
          if Reg = R_None then
+            --  Passed on the stack, need 8 bytes.
             Size := 8;
          else
+            --  Passed by a register.
             Size := 0;
          end if;
       else
diff --git a/src/ortho/mcode/ortho_code-x86-emits.adb b/src/ortho/mcode/ortho_code-x86-emits.adb
index 0e62eb6e3..4753aab85 100644
--- a/src/ortho/mcode/ortho_code-x86-emits.adb
+++ b/src/ortho/mcode/ortho_code-x86-emits.adb
@@ -1391,6 +1391,7 @@ package body Ortho_Code.X86.Emits is
       Gen_Call (Sym);
 
       if Abi.Flag_Sse2 and then not Flags.M64 and then Mode in Mode_Fp then
+         --  Convert return value from St0 to Xmm0.
          declare
             Sslot : constant Int32 := -Int32 (Cur_Subprg.Target.Fp_Slot);
          begin
diff --git a/src/ortho/mcode/ortho_code-x86-insns.adb b/src/ortho/mcode/ortho_code-x86-insns.adb
index 8d6e5be69..099f73e2a 100644
--- a/src/ortho/mcode/ortho_code-x86-insns.adb
+++ b/src/ortho/mcode/ortho_code-x86-insns.adb
@@ -1230,7 +1230,8 @@ package body Ortho_Code.X86.Insns is
       --  Generate code for arguments (if any).
       Gen_Call_Arg (Get_Arg_Link (Stmt), Get_Subprg_Interfaces (Subprg), Pnum);
 
-      --  Clobber registers.
+      --  Clobber registers.  They are saved in reserved slots (at the top
+      --  of the frame).
       if Flags.M64 then
          Clobber_Caller_Saved_Registers_64 (Get_Arg_Link (Stmt), Subprg, Pnum);
       else