Unexpected evaluation in conditional branch

[Dibyendu Majumdar]

Hi Dave,

I have scenario where the conditional branch is evaluating the result
of a comparison - one of the operands of the comparison is a function
call. The generated code appears to evaluate the comparison twice -
once for the true branch and once for the false branch - which is not
what I am expecting. I can of course store the result of the
comparison in a local variable and then perform conditional branch on
the variable but I wanted to check whether this behaviour is as
expected.

My code is this:

  gcc_jit_rvalue *ra = ravi_emit_get_register(def, A);
  gcc_jit_rvalue *nresults_const = gcc_jit_context_new_rvalue_from_int(
      def->function_context, def->ravi->types->C_intT, nresults);
  gcc_jit_rvalue *precall_result = ravi_function_call3_rvalue(
      def, def->ravi->types->luaD_precallT, gcc_jit_param_as_rvalue(def->L), ra,
      nresults_const);
  gcc_jit_rvalue *zero_const = gcc_jit_context_new_rvalue_from_int(
      def->function_context, def->ravi->types->C_intT, 0);
  gcc_jit_rvalue *precall_bool = gcc_jit_context_new_comparison(
      def->function_context, NULL, GCC_JIT_COMPARISON_EQ, precall_result,
      zero_const);

  gcc_jit_block *then_block = gcc_jit_function_new_block(
      def->jit_function, unique_name(def, "OP_CALL_if_lua_function", pc));
  gcc_jit_block *else_block = gcc_jit_function_new_block(
      def->jit_function, unique_name(def, "OP_CALL_else_lua_function", pc));
  gcc_jit_block *end_block = gcc_jit_function_new_block(
      def->jit_function, unique_name(def, "OP_CALL_done", pc));

  ravi_emit_conditional_branch(def, precall_bool, then_block, else_block);


The output I get is this:

  base = L->ci->u.l.base;
  &base[(int)1]->value_.b = (int)1;
  &base[(int)1]->tt_ = (int)1;
  base = L->ci->u.l.base;
  L->top = &base[(int)2];
  if (luaD_precall (L, &base[(int)0], (int)0) == (int)0) goto
OP_CALL_if_lua_function_2_1; else goto OP_CALL_else_lua_function_2_2;

OP_CALL_if_lua_function_2_1:
  (void)luaV_execute (L);
  goto OP_CALL_done_2_3;

OP_CALL_else_lua_function_2_2:
  if (luaD_precall (L, &base[(int)0], (int)0) == (int)1) goto
OP_CALL_if_C_function_2_4; else goto OP_CALL_done_2_3;


Regards
Dibyendu