I noticed this while working on std::optional, the full blown cselim with Data
references
hanldes the case where there are a few stores on either side of the branch that
don't
interfer with the other stores. But we can handle the limited case where the
last "store"
on one of the branches was a clobber. Since the clobber is not a real store it
can
be "safely" bypassed without checking the lhs.
This was found by looking into std::optional::reset code gen.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/127053
gcc/ChangeLog:
* tree-ssa-phiopt.cc (trailing_store_in_bb): Rename vphi to
vuse_only.
(cond_if_else_store_replacement_limited): Add case if
cond_if_else_store_replacement_1 failed for if one
of the stores were a clobber.
gcc/testsuite/ChangeLog:
* g++.dg/tree-ssa/cselim-2.C: New test.
Signed-off-by: Andrea Pinski <[email protected]>
---
gcc/testsuite/g++.dg/tree-ssa/cselim-2.C | 23 ++++++++++++++++
gcc/tree-ssa-phiopt.cc | 34 +++++++++++++++++++-----
2 files changed, 51 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cselim-2.C
diff --git a/gcc/testsuite/g++.dg/tree-ssa/cselim-2.C
b/gcc/testsuite/g++.dg/tree-ssa/cselim-2.C
new file mode 100644
index 00000000000..9c040f9d183
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/cselim-2.C
@@ -0,0 +1,23 @@
+// PR tree-optimization/127053
+// { dg-do compile }
+// { dg-options "-O2 -ftree-cselim -fdump-tree-phiopt1-details" }
+// testcase reduced from std::optional::reset.
+
+void sink(int*);
+typedef int T;
+
+int f(int b, T *c)
+{
+ int a;
+ sink(&a);
+ if (b)
+ {
+ a = 0;
+ c->~T();
+ }
+ else
+ a = 0;
+ return a;
+}
+
+// { dg-final { scan-tree-dump "factoring out stores" "phiopt1" } }
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index ddb2e353cf4..14a6b8262bb 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -3547,12 +3547,12 @@ cond_if_else_store_replacement_1 (basic_block then_bb,
basic_block else_bb,
}
/* Return the last store in BB with VDEF or NULL if there are
- loads following the store. VPHI is where the only use of the
+ loads following the store. VUSE_ONLY is where the only use of the
vdef should be. If ONLYONESTORE is true, then the store is
the only store in the BB. */
static gimple *
-trailing_store_in_bb (basic_block bb, tree vdef, gphi *vphi, bool onlyonestore)
+trailing_store_in_bb (basic_block bb, tree vdef, gimple *vuse_only, bool
onlyonestore)
{
if (SSA_NAME_IS_DEFAULT_DEF (vdef))
return NULL;
@@ -3570,12 +3570,12 @@ trailing_store_in_bb (basic_block bb, tree vdef, gphi
*vphi, bool onlyonestore)
/* Verify there is no load or store after the store, the vdef of the store
- should only be used by the vphi joining the 2 bbs. */
+ should only be used by the vuse_only. */
use_operand_p use_p;
gimple *use_stmt;
if (!single_imm_use (gimple_vdef (store), &use_p, &use_stmt))
return NULL;
- if (use_stmt != vphi)
+ if (use_stmt != vuse_only)
return NULL;
return store;
@@ -3900,8 +3900,30 @@ cond_if_else_store_replacement_limited (basic_block
then_bb, basic_block else_bb
if (!else_assign)
return false;
- return cond_if_else_store_replacement_1 (then_bb, else_bb, join_bb,
- then_assign, else_assign, vphi);
+ if (!cond_if_else_store_replacement_1 (then_bb, else_bb, join_bb,
+ then_assign, else_assign, vphi))
+ {
+ if (!flag_expensive_optimizations
+ || gimple_clobber_p (then_assign) == gimple_clobber_p (else_assign))
+ return false;
+ if (gimple_clobber_p (then_assign))
+ {
+ then_assign = trailing_store_in_bb (then_bb, gimple_vuse
(then_assign),
+ then_assign, true);
+ if (!then_assign)
+ return false;
+ }
+ else
+ {
+ else_assign = trailing_store_in_bb (else_bb, gimple_vuse
(else_assign),
+ else_assign, true);
+ if (!else_assign)
+ return false;
+ }
+ return cond_if_else_store_replacement_1 (then_bb, else_bb, join_bb,
+ then_assign, else_assign, vphi);
+ }
+ return true;
}
/* Conditional store replacement. We already know
--
2.43.0
