Hi,
this patch fixes PR65511.
For the testcase, before transform_to_exit_first_loop the back-edge probability
is 99%:
...
;; basic block 5, loop depth 1, count 0, freq 7920, maybe hot
;; prev block 11, next block 6, flags: (NEW)
;; pred: 11 [100.0%] (FALLTHRU)
;; 7 [100.0%] (FALLTHRU,EXECUTABLE)
# .MEM_15 = PHI <.MEM_3(D)(11), .MEM_9(7)>
# ivtmp_22 = PHI <0(11), ivtmp_23(7)>
# RANGE [0, 1000] NONZERO 1023
i_14 = ivtmp_22;
# VUSE <.MEM_15>
_6 = aD.1830[i_14];
# VUSE <.MEM_15>
_7 = bD.1831[i_14];
# RANGE [0, 4294967295]
_8 = _6 + _7;
# .MEM_9 = VDEF <.MEM_15>
cD.1832[i_14] = _8;
# RANGE [1, 1001] NONZERO 1023
i_10 = i_14 + 1;
# RANGE [0, 1000] NONZERO 1023
i.0_4 = (unsigned intD.9) i_10;
if (ivtmp_22 < _12)
goto <bb 7>;
else
goto <bb 6>;
;; succ: 7 [99.0%] (TRUE_VALUE,EXECUTABLE)
;; 6 [1.0%] (FALSE_VALUE,EXECUTABLE)
...
But after transform_to_exit_first_loop, the back-edge has a probability of 100%:
...
;; basic block 5, loop depth 1, count 0, freq 7920, maybe hot
;; prev block 11, next block 13, flags: (NEW)
;; pred: 11 [100.0%] (FALLTHRU)
;; 7 [100.0%] (FALLTHRU,EXECUTABLE)
# .MEM_24 = PHI <.MEM_3(D)(11), .MEM_9(7)>
# ivtmp_25 = PHI <0(11), ivtmp_23(7)>
if (ivtmp_25 < _12)
goto <bb 13>;
else
goto <bb 14>;
;; succ: 13 [100.0%] (TRUE_VALUE,EXECUTABLE)
;; 14 (FALSE_VALUE,EXECUTABLE)
...
This patch fixes that:
...
;; basic block 5, loop depth 1, count 0, freq 7920, maybe hot
;; prev block 11, next block 13, flags: (NEW)
;; pred: 11 [100.0%] (FALLTHRU)
;; 7 [100.0%] (FALLTHRU,EXECUTABLE)
# .MEM_24 = PHI <.MEM_3(D)(11), .MEM_9(7)>
# ivtmp_25 = PHI <0(11), ivtmp_23(7)>
if (ivtmp_25 < _12)
goto <bb 13>;
else
goto <bb 14>;
;; succ: 13 [99.0%] (TRUE_VALUE,EXECUTABLE)
;; 14 [1.0%] (FALSE_VALUE,EXECUTABLE)
...
Bootstrapped and reg-tested on x86_64.
OK for, I'd guess, stage1?
Thanks,
- Tom
Fix edge probabilities in gimple_duplicate_sese_tail
2015-03-27 Tom de Vries <t...@codesourcery.com>
PR tree-optimization/65511
* tree-cfg.c (gimple_duplicate_sese_tail): Fix edge probabilities.
* gcc.dg/parloops-prob.c: New test.
---
gcc/testsuite/gcc.dg/parloops-prob.c | 21 +++++++++++++++++++++
gcc/tree-cfg.c | 3 +++
2 files changed, 24 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/parloops-prob.c
diff --git a/gcc/testsuite/gcc.dg/parloops-prob.c b/gcc/testsuite/gcc.dg/parloops-prob.c
new file mode 100644
index 0000000..a3e767c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parloops-prob.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target pthread } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-fixup_cfg4-all" } */
+
+#define N 1000
+
+unsigned int a[N];
+unsigned int b[N];
+unsigned int c[N];
+
+void
+f (unsigned int n)
+{
+ int i;
+
+ for (i = 0; i < n; ++i)
+ c[i] = a[i] + b[i];
+}
+
+/* { dg-final { scan-tree-dump-not "freq 0" "fixup_cfg4" } } */
+/* { dg-final { cleanup-tree-dump "fixup_cfg4" } } */
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 64bdc92..c7a7c4d 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -6177,6 +6177,7 @@ gimple_duplicate_sese_tail (edge entry ATTRIBUTE_UNUSED, edge exit ATTRIBUTE_UNU
gphi *phi;
tree def;
struct loop *target, *aloop, *cloop;
+ int exit_prob = exit->probability;
gcc_assert (EDGE_COUNT (exit->src->succs) == 2);
exits[0] = exit;
@@ -6268,6 +6269,8 @@ gimple_duplicate_sese_tail (edge entry ATTRIBUTE_UNUSED, edge exit ATTRIBUTE_UNU
sorig = single_succ_edge (switch_bb);
sorig->flags = exits[1]->flags;
snew = make_edge (switch_bb, nentry_bb, exits[0]->flags);
+ snew->probability = exit_prob;
+ sorig->probability = REG_BR_PROB_BASE - exit_prob;
/* Register the new edge from SWITCH_BB in loop exit lists. */
rescan_loop_exit (snew, true, false);
--
1.9.1
