Smaller C: Support structure passing/returning by value on MIPS

src/cmd/smlrc/Makefile

@@ -4,7 +4,7 @@ include $(TOPSRC)/target.mk
 CFLAGS          = -Os -Wall -DMIPS -DNO_ANNOTATIONS -DNO_PREPROCESSOR \
                   -DNO_PPACK -D_RETROBSD -D__SMALLER_C_SCHAR__ \
                   -D__SMALLER_C__ -D__SMALLER_C_32__ -DSTATIC \
-                  -DNO_EXTRA_WARNS -DSYNTAX_STACK_MAX=2560
+                  -DNO_EXTRA_WARNS -DSYNTAX_STACK_MAX=2530
 
 # For cross compile
 #include $(TOPSRC)/cross.mk

src/cmd/smlrc/cgmips.c

@@ -2188,4 +2188,42 @@ void GenFin(void)
 
     puts2(CodeHeaderFooter[1]);
   }
+
+#ifndef NO_STRUCT_BY_VAL
+  if (StructPushLabel)
+  {
+    int lbl = LabelCnt++;
+
+    puts2(CodeHeaderFooter[0]);
+
+    GenNumLabel(StructPushLabel);
+
+    puts2("\tmove\t$6, $5\n"
+          "\taddiu\t$6, $6, 3\n"
+          "\tli\t$3, -4\n"
+          "\tand\t$6, $6, $3\n"
+          "\tsubu\t$29, $29, $6\n"
+          "\taddiu\t$3, $29, 16\n"
+          "\tmove\t$2, $3");
+    GenNumLabel(lbl);
+    puts2("\tlbu\t$6, 0($4)\n"
+          "\taddiu\t$4, $4, 1\n"
+          "\taddiu\t$5, $5, -1\n"
+          "\tsb\t$6, 0($3)\n"
+          "\taddiu\t$3, $3, 1");
+    printf2("\tbne\t$5, $0, "); GenPrintNumLabel(lbl);
+    puts2("");
+#ifdef REORDER_WORKAROUND
+    GenNop();
+#endif
+    puts2("\tlw\t$2, 0($2)\n"
+          "\taddiu\t$29, $29, 4\n"
+          "\tj\t$31");
+#ifdef REORDER_WORKAROUND
+    GenNop();
+#endif
+
+    puts2(CodeHeaderFooter[1]);
+  }
+#endif
 }

src/cmd/smlrc/smlrc.c

@@ -60,12 +60,7 @@ either expressed or implied, of the FreeBSD Project.
 #endif
 
 // Passing and returning structures by value is currenly supported
-// on x86 only
+// on x86 and MIPS only
-#ifdef MIPS
-#ifndef NO_STRUCT_BY_VAL
-#define NO_STRUCT_BY_VAL
-#endif
-#endif
 #ifdef TR3200
 #ifndef NO_STRUCT_BY_VAL
 #define NO_STRUCT_BY_VAL
@@ -4161,12 +4156,12 @@ int exprval(int* idx, int* ExprTypeSynPtr, int* ConstExpr)
 #ifndef NO_STRUCT_BY_VAL
         // Count the implicit param/arg for returned structure
         c += retStruct;
+        // Correct the value by which the stack pointer
+        // will be incremented after the call
+        c += structSize / SizeOfWord;
 #endif
         stack[1 + *idx][1] = stack[i][1] = c * SizeOfWord;
 #ifndef NO_STRUCT_BY_VAL
-        // Correct the value by which the stack pointer
-        // will be incremented after the call
-        stack[i][1] += structSize;
         // If a structure is returned, transform
         // fxn(pretval, args) into *(fxn(pretval, args), pretval)
         if (retStruct)