Hi,
This patch implements a new opportunity of jump threading for PR77820.
In this optimization, conditional jumps are merged with unconditional
jump. And then moving CMP result to GPR is eliminated.
This version is based on the proposal of Richard, Jeff and Andrew, and
refined to incorporate comments. Thanks for the reviews!
Bootstrapped and tested on powerpc64le and powerpc64be with no
regressions (one case is improved) and new testcases are added. Is this
ok for trunk?
Example of this opportunity looks like below:
<P0>
p0 = a CMP b
goto <X>;
<P1>
p1 = c CMP d
goto <X>;
<X>
# phi = PHI <p0 (P0), p1 (P1)>
if (phi != 0) goto <Y>; else goto <Z>;
Could be transformed to:
<P0>
p0 = a CMP b
if (p0 != 0) goto <Y>; else goto <Z>;
<P1>
p1 = c CMP d
if (p1 != 0) goto <Y>; else goto <Z>;
This optimization eliminates:
1. saving CMP result: p0 = a CMP b.
2. additional CMP on branch: if (phi != 0).
3. converting CMP result if there is phi = (INT_CONV) p0 if there is.
Thanks!
Jiufu Guo
[gcc]
2019-05-28 Jiufu Guo <guoji...@linux.ibm.com>
Lijia He <heli...@linux.ibm.com>
PR tree-optimization/77820
* tree-ssa-threadedge.c
(edge_forwards_cmp_to_conditional_jump_through_empty_bb_p): New
function.
(thread_across_edge): Add call to
edge_forwards_cmp_to_conditional_jump_through_empty_bb_p.
[gcc/testsuite]
2019-05-28 Jiufu Guo <guoji...@linux.ibm.com>
Lijia He <heli...@linux.ibm.com>
PR tree-optimization/77820
* gcc.dg/tree-ssa/phi_on_compare-1.c: New testcase.
* gcc.dg/tree-ssa/phi_on_compare-2.c: New testcase.
* gcc.dg/tree-ssa/phi_on_compare-3.c: New testcase.
* gcc.dg/tree-ssa/phi_on_compare-4.c: New testcase.
* gcc.dg/tree-ssa/split-path-6.c: Update testcase.
---
gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c | 30 ++++++++++
gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c | 23 +++++++
gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c | 25 ++++++++
gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c | 40 +++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c | 2 +-
gcc/tree-ssa-threadedge.c | 76 +++++++++++++++++++++++-
6 files changed, 192 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
new file mode 100644
index 0000000..5227c87
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast -fdump-tree-vrp1" } */
+
+void g (int);
+void g1 (int);
+
+void
+f (long a, long b, long c, long d, long x)
+{
+ _Bool t;
+ if (x)
+ {
+ g (a + 1);
+ t = a < b;
+ c = d + x;
+ }
+ else
+ {
+ g (b + 1);
+ a = c + d;
+ t = c > d;
+ }
+
+ if (t)
+ g1 (c);
+
+ g (a);
+}
+
+/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
new file mode 100644
index 0000000..eaf89bb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast -fdump-tree-vrp1" } */
+
+void g (void);
+void g1 (void);
+
+void
+f (long a, long b, long c, long d, int x)
+{
+ _Bool t;
+ if (x)
+ t = c < d;
+ else
+ t = a < b;
+
+ if (t)
+ {
+ g1 ();
+ g ();
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
new file mode 100644
index 0000000..d5a1e0b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast -fdump-tree-vrp1" } */
+
+void g (void);
+void g1 (void);
+
+void
+f (long a, long b, long c, long d, int x)
+{
+ int t;
+ if (x)
+ t = a < b;
+ else if (d == x)
+ t = c < b;
+ else
+ t = d > c;
+
+ if (t)
+ {
+ g1 ();
+ g ();
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
new file mode 100644
index 0000000..53acabc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
@@ -0,0 +1,40 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast -fdump-tree-vrp1" } */
+
+void g (int);
+void g1 (int);
+
+void
+f (long a, long b, long c, long d, int x)
+{
+ int t;
+ _Bool l1 = 0, l2 = 0;
+ if (x)
+ {
+ g (a);
+ c = a + b;
+ t = a < b;
+ l1 = 1;
+ }
+ else
+ {
+ g1 (b);
+ t = c > d;
+ d = c + b;
+ l2 = 1;
+ }
+
+ if (t)
+ {
+ if (l1 | l2)
+ g1 (c);
+ }
+ else
+ {
+ g (d);
+ g1 (a + b);
+ }
+ g (c + d);
+}
+
+/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
index e9b4f26..1d7b587 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
@@ -69,4 +69,4 @@ lookharder (string)
}
}
-/* { dg-final { scan-tree-dump-times "Duplicating join block" 3 "split-paths"
} } */
+/* { dg-final { scan-tree-dump-times "Duplicating join block" 2 "split-paths"
} } */
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index c3ea2d6..36c413a 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -1157,6 +1157,74 @@ thread_through_normal_block (edge e,
return 0;
}
+/* There are basic blocks look like:
+ <P0>
+ p0 = a CMP b ; or p0 = (INT) (a CMP b)
+ goto <X>;
+
+ <P1>
+ p1 = c CMP d
+ goto <X>;
+
+ <X>
+ # phi = PHI <p0 (P0), p1 (P1)>
+ if (phi != 0) goto <Y>; else goto <Z>;
+
+ Then, edge (P0,X) or (P1,X) could be marked as EDGE_START_JUMP_THREAD
+ And edge (X,Y), (X,Z) is EDGE_COPY_SRC_JOINER_BLOCK
+
+ Return true if E is (P0,X) or (P1,X) */
+
+bool
+edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (edge e)
+{
+ basic_block bb = e->dest;
+
+ /* See if there is only one stmt which is gcond. */
+ gimple *gs = last_and_only_stmt (bb);
+ if (gs == NULL || gimple_code (gs) != GIMPLE_COND)
+ return false;
+
+ /* See if gcond's cond is "(phi !=/== 0/1)" in the basic block. */
+ tree cond = gimple_cond_lhs (gs);
+ enum tree_code code = gimple_cond_code (gs);
+ tree rhs = gimple_cond_rhs (gs);
+ if (TREE_CODE (cond) != SSA_NAME
+ || (code != NE_EXPR && code != EQ_EXPR)
+ || (!integer_onep (rhs) && !integer_zerop (rhs)))
+ return false;
+ gphi *phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (cond));
+ if (phi == NULL || gimple_bb (phi) != bb)
+ return false;
+
+ /* Check if phi's incoming value is CMP. */
+ gimple *def;
+ tree value = PHI_ARG_DEF_FROM_EDGE (phi, e);
+ if (TREE_CODE (value) == SSA_NAME
+ && has_single_use (value)
+ && is_gimple_assign (SSA_NAME_DEF_STMT (value)))
+ def = SSA_NAME_DEF_STMT (value);
+ else
+ return false;
+
+ /* Or if it is (INT) (a CMP b). */
+ if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def)))
+ {
+ value = gimple_assign_rhs1 (def);
+ if (TREE_CODE (value) == SSA_NAME
+ && has_single_use (value)
+ && is_gimple_assign (SSA_NAME_DEF_STMT (value)))
+ def = SSA_NAME_DEF_STMT (value);
+ else
+ return false;
+ }
+
+ if (TREE_CODE_CLASS (gimple_assign_rhs_code (def)) != tcc_comparison)
+ return false;
+
+ return true;
+}
+
/* We are exiting E->src, see if E->dest ends with a conditional
jump which has a known value when reached via E.
@@ -1317,10 +1385,12 @@ thread_across_edge (gcond *dummy_cond,
/* If we were able to thread through a successor of E->dest, then
record the jump threading opportunity. */
- if (found)
+ if (found
+ || edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (e))
{
- propagate_threaded_block_debug_into (path->last ()->e->dest,
- taken_edge->dest);
+ if (taken_edge->dest != path->last ()->e->dest)
+ propagate_threaded_block_debug_into (path->last ()->e->dest,
+ taken_edge->dest);
register_jump_thread (path);
}
else
--
2.7.4
