Organize frames in a real linked list on ARM

Change the linking of the frames on ARM. Instead of having fp points 12
bytes above where the old fp is stored, let fp points where the old fp
is stored. That is, we switch from:

|   .    |
|   .    |
|   .    |
|        |
| params | <-- fp
 --------
| oldlr  |
 --------
| oldip  |
 --------
| oldfp  |
 --------

to:

|   .    |
|   .    |
|   .    |
|        |
| params |
 --------
| oldlr  |
 --------
| oldip  |
 --------
| oldfp  | <-- fp
 --------

1 files changed, 4 insertions, 5 deletions

diff --git a/arm-gen.c b/arm-gen.c
index 99f70cd..e3e502b 100644
--- a/arm-gen.c
+++ b/arm-gen.c
@@ -1152,6 +1152,7 @@ void gfunc_prolog(CType *func_type)
   {
     n++;
     struct_ret = 1;
+    func_vc = 12; /* Offset from fp of the place to store the result */
   }
   for(sym2=sym->next;sym2 && (n<4 || nf<16);sym2=sym2->next) {
     size = type_size(&sym2->type, &align);
@@ -1165,8 +1166,6 @@ void gfunc_prolog(CType *func_type)
     if (n < 4)
       n += (size + 3) / 4;
   }
-  if (struct_ret)
-    func_vc = nf * 4;
   o(0xE1A0C00D); /* mov ip,sp */
   if(variadic)
     n=4;
@@ -1185,7 +1184,7 @@ void gfunc_prolog(CType *func_type)
     o(0xED2D0A00|nf); /* save s0-s15 on stack if needed */
   }
   o(0xE92D5800); /* save fp, ip, lr */
-  o(0xE28DB00C); /* add fp, sp, #12 */
+  o(0xE1A0B00D); /* mov fp, sp */
   func_sub_sp_offset = ind;
   o(0xE1A00000); /* nop, leave space for stack adjustment in epilogue */
   {
@@ -1227,7 +1226,7 @@ from_stack:
         addr = (n + nf + sn) * 4;
         sn += size;
       }
-      sym_push(sym->v & ~SYM_FIELD, type, VT_LOCAL | lvalue_type(type->t), addr);
+      sym_push(sym->v & ~SYM_FIELD, type, VT_LOCAL | lvalue_type(type->t), addr+12);
     }
   }
   last_itod_magic=0;
@@ -1252,7 +1251,7 @@ void gfunc_epilog(void)
     }
   }
 #endif
-  o(0xE91BA800); /* restore fp, sp, pc */
+  o(0xE89BA800); /* restore fp, sp, pc */
   diff = (-loc + 3) & -4;
 #ifdef TCC_ARM_EABI
   if(!leaffunc)