> Hi,
>
> builtin_expect should be a NOP in size_estimation. Indeed, the call
> stmt itself is 0 weight in size and time. But it may introduce
> an extra relation expr which has non-zero size/time. The end result
> is: for w/ and w/o builtin_expect, we have different size/time estimation
> for early inlining.
>
> This patch fixes this problem.
>
> -Rong
> 2013-09-26 Rong Xu <x...@google.com>
>
> * ipa-inline-analysis.c (estimate_function_body_sizes): fix
> the size estimation for builtin_expect.
This seems fine with an comment in the code what it is about.
I also think we want to support mutiple builtin_expects in a BB so perhaps
we want to have pointer set of statements to ignore?
To avoid spagetti code, please just move the new logic into separate functions.
Honza
>
> Index: ipa-inline-analysis.c
> ===================================================================
> --- ipa-inline-analysis.c (revision 202638)
> +++ ipa-inline-analysis.c (working copy)
> @@ -2266,6 +2266,8 @@ estimate_function_body_sizes (struct cgraph_node *
> /* Estimate static overhead for function prologue/epilogue and alignment.
> */
> int overhead = PARAM_VALUE (PARAM_INLINE_FUNCTION_OVERHEAD_SIZE);
> int size = overhead;
> + gimple fix_expect_builtin;
> +
> /* Benefits are scaled by probability of elimination that is in range
> <0,2>. */
> basic_block bb;
> @@ -2359,14 +2361,73 @@ estimate_function_body_sizes (struct cgraph_node *
> }
> }
>
> + fix_expect_builtin = NULL;
> for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
> {
> gimple stmt = gsi_stmt (bsi);
> + if (gimple_call_builtin_p (stmt, BUILT_IN_EXPECT))
> + {
> + tree var = gimple_call_lhs (stmt);
> + tree arg = gimple_call_arg (stmt, 0);
> + use_operand_p use_p;
> + gimple use_stmt;
> + bool match = false;
> + bool done = false;
> + gcc_assert (var && arg);
> + gcc_assert (TREE_CODE (var) == SSA_NAME);
> +
> + while (TREE_CODE (arg) == SSA_NAME)
> + {
> + gimple stmt_tmp = SSA_NAME_DEF_STMT (arg);
> + switch (gimple_assign_rhs_code (stmt_tmp))
> + {
> + case LT_EXPR:
> + case LE_EXPR:
> + case GT_EXPR:
> + case GE_EXPR:
> + case EQ_EXPR:
> + case NE_EXPR:
> + match = true;
> + done = true;
> + break;
> + case NOP_EXPR:
> + break;
> + default:
> + done = true;
> + break;
> + }
> + if (done)
> + break;
> + arg = gimple_assign_rhs1 (stmt_tmp);
> + }
> +
> + if (match && single_imm_use (var, &use_p, &use_stmt))
> + {
> + if (gimple_code (use_stmt) == GIMPLE_COND)
> + {
> + fix_expect_builtin = use_stmt;
> + }
> + }
> +
> + /* we should see one builtin_expert call in one bb. */
> + break;
> + }
> + }
> +
> + for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
> + {
> + gimple stmt = gsi_stmt (bsi);
> int this_size = estimate_num_insns (stmt, &eni_size_weights);
> int this_time = estimate_num_insns (stmt, &eni_time_weights);
> int prob;
> struct predicate will_be_nonconstant;
>
> + if (stmt == fix_expect_builtin)
> + {
> + this_size--;
> + this_time--;
> + }
> +
> if (dump_file && (dump_flags & TDF_DETAILS))
> {
> fprintf (dump_file, " ");
