implement lookupswitch

Makefile

@@ -7,7 +7,7 @@ CC ?= gcc
 ARCH = -m32
 CFLAGS += -Wall -Werror -Wfatal-errors -Wno-error=unused-variable -fstack-protector -std=c2x -g
 CFLAGS += -DDEBUG
-#CFLAGS += -DDEBUG_PRINT
+CFLAGS += -DDEBUG_PRINT
 OPT ?= -O0
 DEPFLAGS = -MMD -MP
 

c/decode.c

@@ -82,11 +82,22 @@ static inline int32_t aligned_s4(const void * buf)
 #define TABLESWITCH_NEXT_PC \
   (args + (3 * 4) + ((highbyte - lowbyte + 1) * 4))
 
-#define LOOKUPSWITCH_ARGS assert(false);
+#define LOOKUPSWITCH_ARGS                            \
+  uint32_t args = ((pc + 1) + 3) & (~3);             \
+  int32_t defaultbyte = aligned_s4(&code[args + 0]); \
+  int32_t npairs = aligned_s4(&code[args + 4]);      \
+  const int32_t * table = (const int32_t *)&code[args + 8];
 
-#define LOOKUPSWITCH_PRINT_ARGS()
+#define LOOKUPSWITCH_PRINT_ARGS()                                       \
+  do {                                                                  \
+    for (int i = 0; i < npairs; i++) {                                  \
+      debugf("  %d: %d\n", aligned_s4(&table[i * 2]), aligned_s4(&table[i * 2 + 1])); \
+    }                                                                   \
+    debugf("default: %d\n", defaultbyte);                               \
+  } while (0);
 
-#define LOOKUPSWITCH_NEXT_PC 0
+#define LOOKUPSWITCH_NEXT_PC \
+  (args + (2 * 4) + (npairs * 2 * 4))
 
 #define WIDE_ARGS assert(false);
 

c/decode.inc.c

@@ -2165,7 +2165,7 @@ void decode_execute_instruction(struct vm * vm, const uint8_t * code, uint32_t p
     {
       LOOKUPSWITCH_ARGS;
       vm->current_frame->next_pc = LOOKUPSWITCH_NEXT_PC;
-      op_lookupswitch(vm);
+      op_lookupswitch(vm, defaultbyte, npairs, table);
       break;
     }
     case 172: // ireturn

c/execute.c

@@ -1467,9 +1467,18 @@ void op_lneg(struct vm * vm)
   operand_stack_push_u64(vm->current_frame, result);
 }
 
-void op_lookupswitch(struct vm * vm)
+void op_lookupswitch(struct vm * vm, int32_t defaultbyte, int32_t npairs, const int32_t * table)
 {
-  assert(!"op_lookupswitch");
+  int32_t key = operand_stack_pop_u32(vm->current_frame);
+  for (int i = 0; i < npairs; i++) {
+    int32_t match = BE_BSWAP32(table[i * 2]);
+    if (key == match) {
+      int32_t offset = BE_BSWAP32(table[i * 2 + 1]);
+      vm->current_frame->pc = vm->current_frame->pc + offset;
+      return;
+    }
+  }
+  vm->current_frame->pc = vm->current_frame->pc + defaultbyte;
 }
 
 void op_lor(struct vm * vm)

c/execute.h

@@ -177,7 +177,7 @@ void op_lload_2(struct vm * vm);
 void op_lload_3(struct vm * vm);
 void op_lmul(struct vm * vm);
 void op_lneg(struct vm * vm);
-void op_lookupswitch(struct vm * vm);
+void op_lookupswitch(struct vm * vm, int32_t defaultbyte, int32_t npairs, const int32_t * table);
 void op_lor(struct vm * vm);
 void op_lrem(struct vm * vm);
 void op_lreturn(struct vm * vm);

p/LookupSwitch.java

@@ -0,0 +1,18 @@
+package p;
+
+class LookupSwitch {
+    static int foo(int a) {
+        switch (a) {
+        case 1:    return 5;
+        case 10:   return 42;
+        case 100:  return 432;
+        case 1000: return 999;
+        case 10000: return 9999;
+        default: return 123;
+        }
+    }
+
+    public static void main() {
+        foo(10);
+    }
+}