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.
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, " ");
