From d520ee43111861ab0458ab96cd515355c875a528 Mon Sep 17 00:00:00 2001
From: Wolfgang Thaller <wolfgang.thaller@gmx.net>
Date: Thu, 3 Jan 2019 20:59:51 +0100
Subject: [PATCH] attempt to improve code quality for pascal calls

---
 gcc/gcc/calls.c                     | 45 +++++++++++++++--------------
 gcc/gcc/combine-stack-adj.c         |  5 +++-
 gcc/gcc/config/m68k/m68k-passes.def | 22 ++++++++++++++
 gcc/gcc/config/m68k/t-m68k          |  1 +
 4 files changed, 50 insertions(+), 23 deletions(-)
 create mode 100644 gcc/gcc/config/m68k/m68k-passes.def

diff --git a/gcc/gcc/calls.c b/gcc/gcc/calls.c
index 39d492785a..b0d56f580f 100644
--- a/gcc/gcc/calls.c
+++ b/gcc/gcc/calls.c
@@ -564,26 +564,6 @@ emit_call_1 (rtx funexp, tree fntree ATTRIBUTE_UNUSED, tree fndecl ATTRIBUTE_UNU
   else if (!ACCUMULATE_OUTGOING_ARGS && (ecf_flags & ECF_NORETURN) != 0)
     add_args_size_note (call_insn, stack_pointer_delta);
 
-
-  if (is_pascal)
-    {
-      if (valreg)
-        {
-          poly_uint16 modesize = GET_MODE_SIZE (GET_MODE (valreg));
-#ifdef PUSH_ROUNDING
-          modesize = PUSH_ROUNDING (modesize);
-#endif
-          rtx pop_insn = emit_move_insn(valreg,
-                       gen_rtx_MEM( GET_MODE (valreg),
-																stack_pointer_rtx
-                               ));
-      
-				  adjust_stack(gen_int_mode (modesize, Pmode));
-        }
-    }
-
-
-
   if (!ACCUMULATE_OUTGOING_ARGS)
     {
       /* If returning from the subroutine does not automatically pop the args,
@@ -618,6 +598,24 @@ emit_call_1 (rtx funexp, tree fntree ATTRIBUTE_UNUSED, tree fndecl ATTRIBUTE_UNU
      such machines.  */
   else if (maybe_ne (n_popped, 0))
     anti_adjust_stack (gen_int_mode (n_popped, Pmode));
+
+
+  if (is_pascal)
+    {
+      if (valreg)
+        {
+          poly_uint16 modesize = GET_MODE_SIZE (GET_MODE (valreg));
+#ifdef PUSH_ROUNDING
+          modesize = PUSH_ROUNDING (modesize);
+#endif
+          rtx pop_insn = emit_move_insn(valreg,
+                       gen_rtx_MEM( GET_MODE (valreg),
+			            stack_pointer_rtx
+                               ));
+      
+	  adjust_stack(gen_int_mode (modesize, Pmode));
+        }
+    }
 }
 
 /* Determine if the function identified by FNDECL is one with
@@ -4248,7 +4246,6 @@ expand_call (tree exp, rtx target, int ignore)
 	  modesize = PUSH_ROUNDING (modesize);
 #endif
 	  push_block (gen_int_mode (modesize, Pmode), 0, 0);
-	  NO_DEFER_POP;	// ### UNBALANCED
 	}
 
       /* Now store (and compute if necessary) all non-register parms.
@@ -4340,7 +4337,11 @@ expand_call (tree exp, rtx target, int ignore)
       if (TYPE_MODE (rettype) != VOIDmode
 	  && ! structure_value_addr)
 	{
-	  if (pcc_struct_value)
+	  if (is_pascal)
+	    {
+	      valreg = gen_reg_rtx(TYPE_MODE(rettype));
+	    }
+	  else if (pcc_struct_value)
 	    {
 	      valreg = hard_function_value (build_pointer_type (rettype),
 					    fndecl, NULL, (pass == 0));
diff --git a/gcc/gcc/combine-stack-adj.c b/gcc/gcc/combine-stack-adj.c
index 4573dc2a87..8b50b8a65d 100644
--- a/gcc/gcc/combine-stack-adj.c
+++ b/gcc/gcc/combine-stack-adj.c
@@ -726,7 +726,10 @@ public:
     {
       return rest_of_handle_stack_adjustments ();
     }
-
+  virtual opt_pass *clone ()
+    {
+      return new pass_stack_adjustments(m_ctxt);
+    }
 }; // class pass_stack_adjustments
 
 bool
diff --git a/gcc/gcc/config/m68k/m68k-passes.def b/gcc/gcc/config/m68k/m68k-passes.def
new file mode 100644
index 0000000000..0cf1c594fb
--- /dev/null
+++ b/gcc/gcc/config/m68k/m68k-passes.def
@@ -0,0 +1,22 @@
+
+/*
+   Macros that can be used in this file:
+   INSERT_PASS_AFTER (PASS, INSTANCE, TGT_PASS)
+   INSERT_PASS_BEFORE (PASS, INSTANCE, TGT_PASS)
+   REPLACE_PASS (PASS, INSTANCE, TGT_PASS)
+ */
+
+	// insert a stack adjustments (csa) pass early in compilation,
+	// before register allocation.
+	// This allows removing some extraneous moves in connection with pascal functions:
+	// pascal short bar(); pascal void foo(short);
+	// foo(bar());
+	// 
+	// subq #2, sp
+	// jsr bar
+	// move (sp), d0	; <-- otherwise we end up with these two useless instructions
+	// move d0, (sp)	; <-- which are not removed if the register is already allocated
+	//			; <-- when csa figures out that no actual push or pop is needed
+	// jsr foo
+
+  INSERT_PASS_AFTER (pass_combine, 1, pass_stack_adjustments);
diff --git a/gcc/gcc/config/m68k/t-m68k b/gcc/gcc/config/m68k/t-m68k
index 6213ced400..3d75d20264 100644
--- a/gcc/gcc/config/m68k/t-m68k
+++ b/gcc/gcc/config/m68k/t-m68k
@@ -9,3 +9,4 @@ m68k-mac-pragmas.o: $(srcdir)/config/m68k/m68k-mac-pragmas.c
 
 M68K_MLIB_CPU += && (CPU !~ "^m68060") && (CPU !~ "^cpu32") && (CPU !~ "^fidoa")
 
+PASSES_EXTRA += $(srcdir)/config/m68k/m68k-passes.def