In cond_store_replacement_limited, we currently reject any load after the
store; this was done as a simple way out but we can do better and just not
remove the store.
That is we have:
```
MEM0 = val;
_1 = MEM1;
if (_8)
MEM0 = val2;
```
cselim (non limited) and ifcvt would turn this info:
```
MEM0 = val;
_1 = MEM1;
_2 = _8 ? val : val2;
MEM0 = _2;
```
So it would be a good idea to do it in limited too and not depend on the
non-trapping part of cselim. So in the case of the testcases we can remove
the conditional fully and just have 2 stores. DSE will remove the
first store if the load does not alias too.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/126580
gcc/ChangeLog:
* tree-ssa-phiopt.cc (cond_store_replacement_limited): Allow
a load before the store; not removing the store.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/pr126580-1.c: New test.
* gcc.dg/tree-ssa/pr126580-2.c: New test.
Signed-off-by: Andrea Pinski <[email protected]>
---
gcc/testsuite/gcc.dg/tree-ssa/pr126580-1.c | 16 ++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr126580-2.c | 15 +++++++++++++++
gcc/tree-ssa-phiopt.cc | 16 +++++++++++-----
3 files changed, 42 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr126580-1.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr126580-2.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr126580-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr126580-1.c
new file mode 100644
index 00000000000..98115c0ac75
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr126580-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-cselim -fdump-tree-phiopt1-details" } */
+
+int *sink(int*);
+void f(int a, int c, int d, int *e)
+{
+ e = sink(&a);
+ a = d;
+ c = *e;
+ c += a;
+ if (c)
+ a = d|c;
+ sink(&a);
+}
+
+/* { dg-final { scan-tree-dump "Conditional store replacement" "phiopt1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr126580-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr126580-2.c
new file mode 100644
index 00000000000..5e0cd96b371
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr126580-2.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-cselim -fdump-tree-phiopt1-details" } */
+
+
+void f1(int *a, int c, int d, int *e)
+{
+ *a = d;
+ c = *e;
+ c += *a;
+ int t = d|c;
+ if (c)
+ *a = t;
+}
+
+/* { dg-final { scan-tree-dump "Conditional store replacement" "phiopt1" } } */
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index d63a47cc615..7ba763ee90c 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -3695,17 +3695,22 @@ cond_store_replacement_limited (basic_block middle_bb,
basic_block join_bb,
tree vuse = gimple_vuse (store_middle);
imm_use_iterator iter;
gimple *use_stmt;
- /* There can't be any loads between the store and
- the previous store as that might depend on the store.
- FIXME: use alias oracle to check dependancies. */
+ bool has_load = false;
+ /* If there is a load, then just reuse the value and not
+ remove the old store as that might be used by the load. */
FOR_EACH_IMM_USE_STMT (use_stmt, iter, vuse)
{
if (use_stmt != store_middle
&& use_stmt != vphi)
- return false;
+ {
+ has_load = true;
+ break;
+ }
}
other_rhs = gimple_assign_rhs1 (vdef_before);
- beforestore = vdef_before;
+ /* If there is no load, then keep the reference to the store stmt. */
+ if (!has_load)
+ beforestore = vdef_before;
}
}
/*
@@ -3794,6 +3799,7 @@ cond_store_replacement_limited (basic_block middle_bb,
basic_block join_bb,
gsi_remove (&gsi, true);
release_defs (store_middle);
+ /* Remove the store before the conditional if possible. */
if (beforestore)
{
gsi = gsi_for_stmt (beforestore);
--
2.43.0
