On Tue, Sep 28, 2021 at 3:46 AM Jeff Law <jeffreya...@gmail.com> wrote:
>
>
>
> On 9/27/2021 9:00 AM, Aldy Hernandez wrote:
> > Last year I mentioned that -fthread-jumps was being ignored by the
> > majority of our jump threading passes, and Jeff said he'd be in favor
> > of fixing this.
> >
> > This patch remedies the situation, but it does change existing behavior.
> > Currently -fthread-jumps is only enabled for -O2, -O3, and -Os. This
> > means that even if we restricted all jump threading passes with
> > -fthread-jumps, DOM jump threading would still seep through since it
> > runs at -O1.
> >
> > I propose this patch, but it does mean that DOM jump threading would
> > have to be explicitly enabled with -O1 -fthread-jumps. An
> > alternative would be to also offer a specific -fno-dom-threading, but
> > that seems icky.
> >
> > OK pending tests?
> >
> > gcc/ChangeLog:
> >
> > * tree-ssa-threadbackward.c (pass_thread_jumps::gate): Check
> > flag_thread_jumps.
> > (pass_early_thread_jumps::gate): Same.
> > * tree-ssa-threadedge.c (jump_threader::thread_outgoing_edges):
> > Return if !flag_thread_jumps.
> > * tree-ssa-threadupdate.c
> > (jt_path_registry::register_jump_thread): Assert that
> > flag_thread_jumps is true.
> OK. Clearly this is going to be even better once we disentangle
> threading from DOM.
Annoyingly, I had to tweak a few more tests, particularly some
-Wuninitialized -O1 ones which seem to depend on DOM jump threading to
give proper diagnostics. It seems that every change to jump threading
needs tweaks to the Wuninitialized code :-(.
Attached is the patch I have pushed.
Aldy
commit 94591b662aa025a39681dce6bfc889cbe3d1d251
Author: Aldy Hernandez <al...@redhat.com>
Date: Mon Sep 27 16:41:01 2021 +0200
Control all jump threading passes with -fjump-threads.
Last year I mentioned that -fthread-jumps was being ignored by the
majority of our jump threading passes, and Jeff said he'd be in favor
of fixing this.
This patch remedies the situation, but it does change existing behavior.
Currently -fthread-jumps is only enabled for -O2, -O3, and -Os. This
means that even if we restricted all jump threading passes with
-fthread-jumps, DOM jump threading would still seep through since it
runs at -O1.
I propose this patch, but it does mean that DOM jump threading would
have to be explicitly enabled with -O1 -fthread-jumps.
gcc/ChangeLog:
* tree-ssa-threadbackward.c (pass_thread_jumps::gate): Check
flag_thread_jumps.
(pass_early_thread_jumps::gate): Same.
* tree-ssa-threadedge.c (jump_threader::thread_outgoing_edges):
Return if !flag_thread_jumps.
* tree-ssa-threadupdate.c
(jt_path_registry::register_jump_thread): Assert that
flag_thread_jumps is true.
gcc/testsuite/ChangeLog:
* gcc.dg/auto-init-uninit-1.c: Add -fthread-jumps.
* gcc.dg/auto-init-uninit-15.c: Same.
* gcc.dg/guality/example.c: Same.
* gcc.dg/loop-8.c: Same.
* gcc.dg/strlenopt-40.c: Same.
* gcc.dg/tree-ssa/pr18133-2.c: Same.
* gcc.dg/tree-ssa/pr18134.c: Same.
* gcc.dg/uninit-1.c: Same.
* gcc.dg/uninit-pr44547.c: Same.
* gcc.dg/uninit-pr59970.c: Same.
diff --git a/gcc/testsuite/gcc.dg/auto-init-uninit-1.c b/gcc/testsuite/gcc.dg/auto-init-uninit-1.c
index 502db591222..ce8909623ab 100644
--- a/gcc/testsuite/gcc.dg/auto-init-uninit-1.c
+++ b/gcc/testsuite/gcc.dg/auto-init-uninit-1.c
@@ -1,5 +1,5 @@
/* Spurious uninitialized variable warnings, case 1.
Taken from cppfiles.c (merge_include_chains) */
/* { dg-do compile } */
-/* { dg-options "-O -Wuninitialized -ftrivial-auto-var-init=zero" } */
+/* { dg-options "-O -Wuninitialized -fthread-jumps -ftrivial-auto-var-init=zero" } */
#include "uninit-1.c"
diff --git a/gcc/testsuite/gcc.dg/auto-init-uninit-15.c b/gcc/testsuite/gcc.dg/auto-init-uninit-15.c
index 121f0cff274..b8f6e2b57d5 100644
--- a/gcc/testsuite/gcc.dg/auto-init-uninit-15.c
+++ b/gcc/testsuite/gcc.dg/auto-init-uninit-15.c
@@ -5,7 +5,7 @@
But it is of course ok if we warn in bar about uninitialized use
of j. (not xfailed alternative) */
/* { dg-do compile } */
-/* { dg-options "-O1 -Wuninitialized -ftrivial-auto-var-init=zero" } */
+/* { dg-options "-O1 -Wuninitialized -fthread-jumps -ftrivial-auto-var-init=zero" } */
inline int
foo (int i)
diff --git a/gcc/testsuite/gcc.dg/guality/example.c b/gcc/testsuite/gcc.dg/guality/example.c
index 6f1c017a253..37564e55cd1 100644
--- a/gcc/testsuite/gcc.dg/guality/example.c
+++ b/gcc/testsuite/gcc.dg/guality/example.c
@@ -1,4 +1,3 @@
-/* { dg-do run { xfail { ! aarch64*-*-* } } } */
/* { dg-options "-g" } */
/* { dg-xfail-run-if "" aarch64*-*-* "*" { "-O[01g]" } } */
diff --git a/gcc/testsuite/gcc.dg/loop-8.c b/gcc/testsuite/gcc.dg/loop-8.c
index 90ea1c45524..e5218eb4053 100644
--- a/gcc/testsuite/gcc.dg/loop-8.c
+++ b/gcc/testsuite/gcc.dg/loop-8.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O1 -fdump-rtl-loop2_invariant" } */
+/* { dg-options "-O1 -fthread-jumps -fdump-rtl-loop2_invariant" } */
/* { dg-skip-if "unexpected IV" { "hppa*-*-* mips*-*-* visium-*-* powerpc*-*-* riscv*-*-* mmix-*-* vax-*-*" } } */
/* Load immediate on condition is available from z13 on and prevents moving
the load out of the loop, so always run this test with -march=zEC12 that
diff --git a/gcc/testsuite/gcc.dg/strlenopt-40.c b/gcc/testsuite/gcc.dg/strlenopt-40.c
index 7a97ebb8fe5..7b799104708 100644
--- a/gcc/testsuite/gcc.dg/strlenopt-40.c
+++ b/gcc/testsuite/gcc.dg/strlenopt-40.c
@@ -1,7 +1,7 @@
/* PR tree-optimization/83671 - fix for false positive reported by
-Wstringop-overflow does not work with inlining
{ dg-do compile }
- { dg-options "-O1 -fdump-tree-optimized" } */
+ { dg-options "-O1 -fthread-jumps -fdump-tree-optimized" } */
#include "strlenopt.h"
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr18133-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr18133-2.c
index 8717640e327..1b409852189 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr18133-2.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr18133-2.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O1 -fdump-tree-optimized-blocks" } */
+/* { dg-options "-O1 -fthread-jumps -fdump-tree-optimized-blocks" } */
int c, d;
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr18134.c b/gcc/testsuite/gcc.dg/tree-ssa/pr18134.c
index cd40ab2c162..d7f5d241eb9 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr18134.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr18134.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O1 -fdump-tree-optimized" } */
+/* { dg-options "-O1 -fthread-jumps -fdump-tree-optimized" } */
int foo (int a)
{
diff --git a/gcc/testsuite/gcc.dg/uninit-1.c b/gcc/testsuite/gcc.dg/uninit-1.c
index 060ec250ba7..156d34ff732 100644
--- a/gcc/testsuite/gcc.dg/uninit-1.c
+++ b/gcc/testsuite/gcc.dg/uninit-1.c
@@ -1,7 +1,7 @@
/* Spurious uninitialized variable warnings, case 1.
Taken from cppfiles.c (merge_include_chains) */
/* { dg-do compile } */
-/* { dg-options "-O -Wuninitialized" } */
+/* { dg-options "-O -Wuninitialized -fthread-jumps" } */
struct list
{
diff --git a/gcc/testsuite/gcc.dg/uninit-pr44547.c b/gcc/testsuite/gcc.dg/uninit-pr44547.c
index ee1035ad7b8..f1c3b034d14 100644
--- a/gcc/testsuite/gcc.dg/uninit-pr44547.c
+++ b/gcc/testsuite/gcc.dg/uninit-pr44547.c
@@ -1,7 +1,7 @@
/* PR tree-optimization/44547 - -Wuninitialized reports false warning
in nested switch statements
{ dg-do compile }
- { dg-options "-O1 -Wall" } */
+ { dg-options "-O1 -Wall -fthread-jumps" } */
__attribute__ ((noipa)) int test_O1 (int argc)
{
diff --git a/gcc/testsuite/gcc.dg/uninit-pr59970.c b/gcc/testsuite/gcc.dg/uninit-pr59970.c
index 145af657a76..d0c41b8480d 100644
--- a/gcc/testsuite/gcc.dg/uninit-pr59970.c
+++ b/gcc/testsuite/gcc.dg/uninit-pr59970.c
@@ -41,7 +41,7 @@ d_demangle_callback_O1 (const char *mangled)
#pragma GCC pop_options
-#pragma GCC optimize ("Og")
+#pragma GCC optimize ("Og,thread-jumps")
__attribute__ ((noipa)) int
d_demangle_callback_Og (const char *mangled)
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index e6819fe148c..28c7ef8c872 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -943,7 +943,7 @@ public:
bool
pass_thread_jumps::gate (function *fun ATTRIBUTE_UNUSED)
{
- return flag_expensive_optimizations;
+ return flag_thread_jumps && flag_expensive_optimizations;
}
// Try to thread blocks in FUN. Return TRUE if any jump thread paths were
@@ -1013,7 +1013,7 @@ public:
bool
pass_early_thread_jumps::gate (function *fun ATTRIBUTE_UNUSED)
{
- return true;
+ return flag_thread_jumps;
}
unsigned int
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index 0b59cb4845c..a63a9764ff8 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -1196,6 +1196,9 @@ jump_threader::thread_outgoing_edges (basic_block bb)
int flags = (EDGE_IGNORE | EDGE_COMPLEX | EDGE_ABNORMAL);
gimple *last;
+ if (!flag_thread_jumps)
+ return;
+
/* If we have an outgoing edge to a block with multiple incoming and
outgoing edges, then we may be able to thread the edge, i.e., we
may be able to statically determine which of the outgoing edges
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 2b9b8f81274..cf96c903668 100644
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -2822,6 +2822,8 @@ jt_path_registry::cancel_invalid_paths (vec<jump_thread_edge *> &path)
bool
jt_path_registry::register_jump_thread (vec<jump_thread_edge *> *path)
{
+ gcc_checking_assert (flag_thread_jumps);
+
if (!dbg_cnt (registered_jump_thread))
{
path->release ();
