Thanks,
Feng
________________________________________
From: Feng Xue OS <f...@os.amperecomputing.com>
Sent: Thursday, September 3, 2020 5:29 PM
To: Richard Biener; gcc-patches@gcc.gnu.org
Subject: Re: [PATCH 2/2 V3] Simplify plusminus-mult-with-convert expr in
forwprop (PR 94234)
Attach patch file.
Feng
________________________________________
From: Gcc-patches <gcc-patches-boun...@gcc.gnu.org> on behalf of Feng Xue OS
via Gcc-patches <gcc-patches@gcc.gnu.org>
Sent: Thursday, September 3, 2020 5:27 PM
To: Richard Biener; gcc-patches@gcc.gnu.org
Subject: [PATCH 2/2 V3] Simplify plusminus-mult-with-convert expr in forwprop
(PR 94234)
This patch is to handle simplification of plusminus-mult-with-convert expression
as ((T) X) +- ((T) Y), in which at least one of (X, Y) is result of
multiplication.
This is done in forwprop pass. We try to transform it to (T) (X +- Y), and
resort
to gimple-matcher to fold (X +- Y) instead of manually code pattern recognition.
Regards,
Feng
---
2020-09-03 Feng Xue <f...@os.amperecomputing.com>
gcc/
PR tree-optimization/94234
* tree-ssa-forwprop.c (simplify_plusminus_mult_with_convert): New
function.
(fwprop_ssa_val): Move it before its new caller.
(pass_forwprop::execute): Add call to
simplify_plusminus_mult_with_convert.
gcc/testsuite/
PR tree-optimization/94234
* gcc.dg/pr94234-3.c: New test.
From 98c4b97989207dcef5742e9cb451799feafd125e Mon Sep 17 00:00:00 2001
From: Feng Xue <f...@os.amperecomputing.com>
Date: Mon, 17 Aug 2020 23:00:35 +0800
Subject: [PATCH] tree-optimization/94234 - simplify
plusminus-mult-with-convert in forwprop
For expression as ((T) X) +- ((T) Y), and at lease of (X, Y) is result of
multification, try to transform it to (T) (X +- Y), and apply simplification
on (X +- Y) if possible. In this way, we can avoid creating almost duplicated
rule to handle plusminus-mult-with-convert variant.
2020-09-03 Feng Xue <f...@os.amperecomputing.com>
gcc/
PR tree-optimization/94234
* tree-ssa-forwprop.c (simplify_plusminus_mult_with_convert): New
function.
(fwprop_ssa_val): Move it before its new caller.
(pass_forwprop::execute): Add call to
simplify_plusminus_mult_with_convert.
gcc/testsuite/
PR tree-optimization/94234
* gcc.dg/pr94234-3.c: New test.
---
gcc/testsuite/gcc.dg/pr94234-3.c | 42 ++++++++
gcc/tree-ssa-forwprop.c | 168 +++++++++++++++++++++++++++----
2 files changed, 191 insertions(+), 19 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr94234-3.c
diff --git a/gcc/testsuite/gcc.dg/pr94234-3.c b/gcc/testsuite/gcc.dg/pr94234-3.c
new file mode 100644
index 00000000000..9bb9b46bd96
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94234-3.c
@@ -0,0 +1,42 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-forwprop1" } */
+
+typedef __SIZE_TYPE__ size_t;
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+
+ptrdiff_t foo1 (char *a, size_t n)
+{
+ char *b1 = a + 8 * n;
+ char *b2 = a + 8 * (n - 1);
+
+ return b1 - b2;
+}
+
+int use_ptr (char *a, char *b);
+
+ptrdiff_t foo2 (char *a, size_t n)
+{
+ char *b1 = a + 8 * (n - 1);
+ char *b2 = a + 8 * n;
+
+ use_ptr (b1, b2);
+
+ return b1 - b2;
+}
+
+int use_int (int i);
+
+unsigned goo (unsigned m_param, unsigned n_param)
+{
+ unsigned b1 = m_param * (n_param + 2);
+ unsigned b2 = m_param * (n_param + 1);
+ int r = (int)(b1) - (int)(b2);
+
+ use_int (r);
+
+ return r;
+}
+
+/* { dg-final { scan-tree-dump-times "return 8;" 1 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times "return -8;" 1 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times "return m_param" 1 "forwprop1" } } */
diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index e2d008dfb92..7b9d46ec919 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -338,6 +338,25 @@ remove_prop_source_from_use (tree name)
return cfg_changed;
}
+/* Primitive "lattice" function for gimple_simplify. */
+
+static tree
+fwprop_ssa_val (tree name)
+{
+ /* First valueize NAME. */
+ if (TREE_CODE (name) == SSA_NAME
+ && SSA_NAME_VERSION (name) < lattice.length ())
+ {
+ tree val = lattice[SSA_NAME_VERSION (name)];
+ if (val)
+ name = val;
+ }
+ /* We continue matching along SSA use-def edges for SSA names
+ that are not single-use. Currently there are no patterns
+ that would cause any issues with that. */
+ return name;
+}
+
/* Return the rhs of a gassign *STMT in a form of a single tree,
converted to type TYPE.
@@ -1821,6 +1840,133 @@ simplify_rotate (gimple_stmt_iterator *gsi)
return true;
}
+/* Given ((T) X) +- ((T) Y), and at least one of (X, Y) is result of
+ multiplication, if the expr can be transformed to (T) (X +- Y) in terms of
+ two's complement computation, apply simplification on (X +- Y) if it is
+ possible. As a prerequisite, outer result type (T) has precision not more
+ than that of inner operand type. */
+
+static bool
+simplify_plusminus_mult_with_convert (gimple_stmt_iterator *gsi)
+{
+ gimple *stmt = gsi_stmt (*gsi);
+ tree lhs = gimple_assign_lhs (stmt);
+ tree rtype = TREE_TYPE (lhs);
+ tree ctype = NULL_TREE;
+ enum tree_code code = gimple_assign_rhs_code (stmt);
+
+ if (code != PLUS_EXPR && code != MINUS_EXPR)
+ return false;
+
+ /* Skip arithemtic operations that need to preserve overflow for trapping
+ or sanitization. */
+ if (!INTEGRAL_TYPE_P (rtype)
+ || TYPE_OVERFLOW_TRAPS (rtype) || TYPE_OVERFLOW_SANITIZED (rtype))
+ return false;
+
+ tree arg[2] = { gimple_assign_rhs1 (stmt), gimple_assign_rhs2 (stmt) };
+ bool any_single_use = false;
+ bool has_mult = false;
+
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (arg[i]) == SSA_NAME)
+ {
+ tree def_arg, tem;
+ enum tree_code def_code;
+
+ defcodefor_name (arg[i], &def_code, &def_arg, NULL);
+
+ if (!CONVERT_EXPR_CODE_P (def_code))
+ return false;
+
+ if (!ctype)
+ {
+ ctype = TREE_TYPE (def_arg);
+
+ if (!INTEGRAL_TYPE_P (ctype)
+ || TYPE_PRECISION (ctype) < TYPE_PRECISION (rtype))
+ return false;
+
+ if (i)
+ {
+ /* The other operand should be a constant, convert it to
+ inner operand type. */
+ arg[0] = wide_int_to_tree (ctype, wi::to_wide (arg[0]));
+ }
+ }
+ else if (!types_compatible_p (ctype, TREE_TYPE (def_arg)))
+ return false;
+
+ defcodefor_name (def_arg, &def_code, &tem, NULL);
+
+ if (def_code == MULT_EXPR)
+ has_mult = true;
+
+ if (has_single_use (arg[i]))
+ any_single_use = true;
+
+ arg[i] = def_arg;
+ }
+ else if (TREE_CODE (arg[i]) == INTEGER_CST)
+ {
+ if (!ctype)
+ return false;
+
+ /* This operand is a constant, convert it to inner operand type. */
+ arg[i] = wide_int_to_tree (ctype, wi::to_wide (arg[i]));
+ }
+ else
+ return false;
+ }
+
+ if (!has_mult)
+ return false;
+
+ gimple_seq seq = NULL;
+ gimple_seq *pseq = any_single_use ? &seq : NULL;
+ gimple *g;
+ tree val;
+
+ if (TYPE_OVERFLOW_WRAPS (ctype))
+ /* Arithmetic operation on inner operands is using two's complement
+ representation in both overflow and normal cases, UB will not occur
+ and type conversion is trivial. */
+ ;
+ else if (TYPE_SIGN (ctype) == TYPE_SIGN (rtype))
+ /* Both outer result type and inner operand type are signed. Here outer
+ result type should be TYPE_OVERFLOW_UNDEFINED, and inner operand type
+ also does not incur overflow since it is larger. It is UB-safe to do
+ arithmetic operation on large signed type, and truncate to small
+ signed type. */
+ ;
+ else
+ /* Outer result type is unsigned, while inner operand type is signed. We
+ only consider a case, in which final simplification result on inner
+ operands is a simple value (constant or existing SSA). In this
+ situation, although operation on inner operands is of signed type, it
+ computes value for outer unsigned type. So we need not to care about
+ its overflowness. */
+ pseq = NULL;
+
+ if (!(val = gimple_simplify (code, ctype, arg[0], arg[1], pseq,
+ fwprop_ssa_val)))
+ return false;
+
+ if (TREE_CODE (val) == INTEGER_CST)
+ g = gimple_build_assign (lhs, NOP_EXPR,
+ wide_int_to_tree (rtype, wi::to_wide (val)));
+ else if (TREE_CODE (val) == SSA_NAME)
+ g = gimple_build_assign (lhs, NOP_EXPR, val);
+ else
+ return false;
+
+ if (seq)
+ gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
+
+ gsi_replace (gsi, g, false);
+ return true;
+}
/* Check whether an array contains a valid ctz table. */
static bool
@@ -2640,25 +2786,6 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
}
-/* Primitive "lattice" function for gimple_simplify. */
-
-static tree
-fwprop_ssa_val (tree name)
-{
- /* First valueize NAME. */
- if (TREE_CODE (name) == SSA_NAME
- && SSA_NAME_VERSION (name) < lattice.length ())
- {
- tree val = lattice[SSA_NAME_VERSION (name)];
- if (val)
- name = val;
- }
- /* We continue matching along SSA use-def edges for SSA names
- that are not single-use. Currently there are no patterns
- that would cause any issues with that. */
- return name;
-}
-
/* Main entry point for the forward propagation and statement combine
optimizer. */
@@ -3154,6 +3281,9 @@ pass_forwprop::execute (function *fun)
|| code == BIT_XOR_EXPR)
&& simplify_rotate (&gsi))
changed = true;
+ else if (TREE_CODE_CLASS (code) == tcc_binary
+ && simplify_plusminus_mult_with_convert (&gsi))
+ changed = true;
else if (code == VEC_PERM_EXPR)
{
int did_something = simplify_permutation (&gsi);
--
2.17.1
