Hi,
this patch extends tree-ssa-dse to use modref kill summary to clear
live_bytes. This makes it possible to remove calls that are killed
in parts.
I noticed that DSE duplicates the logic of tree-ssa-alias that is mathing bases
of memory accesses. Here operands_equal_p (base1, base, OEP_ADDRESS_OF) is
used.
So it won't work with mismatching memref offsets. We probably want to
commonize
this and add common function that matches bases and returns offset adjustments.
I wonder however if it can catch any cases that the tree-ssa-alias code doesn't?
Other check that stmt_kills_ref_p has and tree-ssa-dse is for
non-call-exceptions.
Bootstrapped/regtested x86_64-linux, OK?
gcc/ChangeLog:
* ipa-modref.c (get_modref_function_summary): New function.
* ipa-modref.h (get_modref_function_summary): Declare.
* tree-ssa-dse.c (clear_live_bytes_for_ref): Break out from ...
(clear_bytes_written_by): ... here; add handling of modref summary.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/modref-dse-4.c: New test.
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index df4612bbff9..8966f9fd2a4 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -724,6 +724,22 @@ get_modref_function_summary (cgraph_node *func)
return r;
}
+/* Get function summary for CALL if it exists, return NULL otherwise.
+ If INTERPOSED is non-NULL set it to true if call may be interposed. */
+
+modref_summary *
+get_modref_function_summary (gcall *call, bool *interposed)
+{
+ tree callee = gimple_call_fndecl (call);
+ if (!callee)
+ return NULL;
+ struct cgraph_node *node = cgraph_node::get (callee);
+ if (!node)
+ return NULL;
+ if (interposed)
+ *interposed = !node->binds_to_current_def_p ();
+ return get_modref_function_summary (node);
+}
+
namespace {
/* Construct modref_access_node from REF. */
diff --git a/gcc/ipa-modref.h b/gcc/ipa-modref.h
index 9e8a30fd80a..72e608864ce 100644
--- a/gcc/ipa-modref.h
+++ b/gcc/ipa-modref.h
@@ -50,6 +50,7 @@ struct GTY(()) modref_summary
};
modref_summary *get_modref_function_summary (cgraph_node *func);
+modref_summary *get_modref_function_summary (gcall *call, bool *interposed);
void ipa_modref_c_finalize ();
void ipa_merge_modref_summary_after_inlining (cgraph_edge *e);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/modref-dse-4.c
b/gcc/testsuite/gcc.dg/tree-ssa/modref-dse-4.c
new file mode 100644
index 00000000000..81aa7dc587c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/modref-dse-4.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse2-details" } */
+struct a {int a,b,c;};
+__attribute__ ((noinline))
+void
+kill_me (struct a *a)
+{
+ a->a=0;
+ a->b=0;
+ a->c=0;
+}
+__attribute__ ((noinline))
+void
+my_pleasure (struct a *a)
+{
+ a->a=1;
+ a->c=2;
+}
+void
+set (struct a *a)
+{
+ kill_me (a);
+ my_pleasure (a);
+ a->b=1;
+}
+/* { dg-final { scan-tree-dump "Deleted dead store: kill_me" "dse2" } } */
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index ce0083a6dab..d2f54b0faad 100644
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -209,6 +209,24 @@ normalize_ref (ao_ref *copy, ao_ref *ref)
return true;
}
+/* Update LIVE_BYTES tracking REF for write to WRITE:
+ Verify we have the same base memory address, the write
+ has a known size and overlaps with REF. */
+static void
+clear_live_bytes_for_ref (sbitmap live_bytes, ao_ref *ref, ao_ref *write)
+{
+ HOST_WIDE_INT start, size;
+
+ if (valid_ao_ref_for_dse (write)
+ && operand_equal_p (write->base, ref->base, OEP_ADDRESS_OF)
+ && known_eq (write->size, write->max_size)
+ && normalize_ref (write, ref)
+ && (write->offset - ref->offset).is_constant (&start)
+ && write->size.is_constant (&size))
+ bitmap_clear_range (live_bytes, start / BITS_PER_UNIT,
+ size / BITS_PER_UNIT);
+}
+
/* Clear any bytes written by STMT from the bitmap LIVE_BYTES. The base
address written by STMT must match the one found in REF, which must
have its base address previously initialized.
@@ -220,20 +238,21 @@ static void
clear_bytes_written_by (sbitmap live_bytes, gimple *stmt, ao_ref *ref)
{
ao_ref write;
+
+ if (gcall *call = dyn_cast <gcall *> (stmt))
+ {
+ bool interposed;
+ modref_summary *summary = get_modref_function_summary (call,
&interposed);
+
+ if (summary && !interposed)
+ for (auto kill : summary->kills)
+ if (kill.get_ao_ref (as_a <gcall *> (stmt), &write))
+ clear_live_bytes_for_ref (live_bytes, ref, &write);
+ }
if (!initialize_ao_ref_for_dse (stmt, &write))
return;
- /* Verify we have the same base memory address, the write
- has a known size and overlaps with REF. */
- HOST_WIDE_INT start, size;
- if (valid_ao_ref_for_dse (&write)
- && operand_equal_p (write.base, ref->base, OEP_ADDRESS_OF)
- && known_eq (write.size, write.max_size)
- && normalize_ref (&write, ref)
- && (write.offset - ref->offset).is_constant (&start)
- && write.size.is_constant (&size))
- bitmap_clear_range (live_bytes, start / BITS_PER_UNIT,
- size / BITS_PER_UNIT);
+ clear_live_bytes_for_ref (live_bytes, ref, &write);
}
/* REF is a memory write. Extract relevant information from it and
