Hi,
This patch handles the comparison of iv against the loop iv initial
value. Previously, we only handle the comparison of iv against its
bound.
Bootstrapped and passed all regression tests.
Ok for google branches?
Thanks,
Dehao
2012-03-29 Dehao Chen <de...@google.com>
* predict.c (predict_iv_comparison): Add the comparison of induction
variable against its initial value.
2012-03-29 Dehao Chen <de...@google.com>
* gcc.dg/predict-5.c: Check if LOOP_IV_COMPARE static predict
heuristic is working properly.
Index: gcc/testsuite/gcc.dg/predict-5.c
===================================================================
--- gcc/testsuite/gcc.dg/predict-5.c (revision 0)
+++ gcc/testsuite/gcc.dg/predict-5.c (revision 0)
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+
+int bar(int);
+
+void foo (int base, int bound)
+{
+ int i, ret = 0;
+ for (i = base; i <= bound; i++)
+ {
+ if (i > base + 2)
+ global += bar (i);
+ else
+ global += bar (i + 1);
+ }
+}
+
+/* { dg-final { scan-tree-dump "loop iv compare heuristics"
"profile_estimate"} } */
+/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
Index: gcc/predict.c
===================================================================
--- gcc/predict.c (revision 185903)
+++ gcc/predict.c (working copy)
@@ -1185,8 +1185,7 @@
return;
}
- if (!expr_coherent_p (loop_bound_var, compare_var)
- || loop_iv_base_var != compare_base)
+ if (loop_iv_base_var != compare_base)
return;
/* If loop bound, base and compare bound are all constents, we can
@@ -1230,34 +1229,52 @@
return;
}
- if ((loop_bound_code == LT_EXPR || loop_bound_code == LE_EXPR)
- && (compare_code == LT_EXPR || compare_code == LE_EXPR))
- predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
- else if ((loop_bound_code == GT_EXPR || loop_bound_code == GE_EXPR)
- && (compare_code == GT_EXPR || compare_code == GE_EXPR))
- predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
- else if (loop_bound_code == NE_EXPR)
- {
- /* If the loop backedge condition is "(i != bound)", we do
- the comparison based on the step of IV:
- * step < 0 : backedge condition is like (i > bound)
- * step > 0 : backedge condition is like (i < bound) */
- gcc_assert (loop_bound_step != 0);
+ if (expr_coherent_p (loop_bound_var, compare_var))
+ {
+ if ((loop_bound_code == LT_EXPR || loop_bound_code == LE_EXPR)
+ && (compare_code == LT_EXPR || compare_code == LE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if ((loop_bound_code == GT_EXPR || loop_bound_code == GE_EXPR)
+ && (compare_code == GT_EXPR || compare_code == GE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if (loop_bound_code == NE_EXPR)
+ {
+ /* If the loop backedge condition is "(i != bound)", we do
+ the comparison based on the step of IV:
+ * step < 0 : backedge condition is like (i > bound)
+ * step > 0 : backedge condition is like (i < bound) */
+ gcc_assert (loop_bound_step != 0);
+ if (loop_bound_step > 0
+ && (compare_code == LT_EXPR
+ || compare_code == LE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if (loop_bound_step < 0
+ && (compare_code == GT_EXPR
+ || compare_code == GE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
+ }
+ else
+ /* The branch is predicted not-taken if loop_bound_code is
+ opposite with compare_code. */
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
+ }
+ else if (expr_coherent_p (loop_iv_base_var, compare_var))
+ {
+ /* For cases like:
+ for (i = s; i < h; i++)
+ if (i > s + 2) ....
+ The branch should be predicted taken. */
if (loop_bound_step > 0
- && (compare_code == LT_EXPR
- || compare_code == LE_EXPR))
+ && (compare_code == GT_EXPR || compare_code == GE_EXPR))
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
else if (loop_bound_step < 0
- && (compare_code == GT_EXPR
- || compare_code == GE_EXPR))
+ && (compare_code == LT_EXPR || compare_code == LE_EXPR))
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
else
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
}
- else
- /* The branch is predicted not-taken if loop_bound_code is
- opposite with compare_code. */
- predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
}
/* Predict edge probabilities by exploiting loop structure. */
