This patch teaches phiopt to look at phis whose arguments are -1 and 0,
and produce negated setcc statements.
Bootstrapped/regtested x86_64-pc-linux-gnu, together with the patch
for pr53138. Ok for mainline?
Paolo
2012-04-27 Paolo Bonzini <bonz...@gnu.org>
* tree-ssa-phiopt.c (conditional_replacement): Replace PHIs
whose arguments are -1 and 0, by negating the result of the
conditional.
2012-04-27 Paolo Bonzini <bonz...@gnu.org>
* gcc.c-torture/execute/20120427-2.c: New testcase.
* gcc.dg/tree-ssa/phi-opt-10.c: New testcase.
Index: tree-ssa-phiopt.c
===================================================================
--- tree-ssa-phiopt.c (revisione 186859)
+++ tree-ssa-phiopt.c (copia locale)
@@ -536,17 +536,21 @@
gimple_stmt_iterator gsi;
edge true_edge, false_edge;
tree new_var, new_var2;
+ bool neg;
/* FIXME: Gimplification of complex type is too hard for now. */
if (TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
|| TREE_CODE (TREE_TYPE (arg1)) == COMPLEX_TYPE)
return false;
- /* The PHI arguments have the constants 0 and 1, then convert
- it to the conditional. */
+ /* The PHI arguments have the constants 0 and 1, or 0 and -1, then
+ convert it to the conditional. */
if ((integer_zerop (arg0) && integer_onep (arg1))
|| (integer_zerop (arg1) && integer_onep (arg0)))
- ;
+ neg = false;
+ else if ((integer_zerop (arg0) && integer_all_onesp (arg1))
+ || (integer_zerop (arg1) && integer_all_onesp (arg0)))
+ neg = true;
else
return false;
@@ -558,7 +562,7 @@
falls through into BB.
There is a single PHI node at the join point (BB) and its arguments
- are constants (0, 1).
+ are constants (0, 1) or (0, -1).
So, given the condition COND, and the two PHI arguments, we can
rewrite this PHI into non-branching code:
@@ -585,12 +589,20 @@
edge so that we know when to invert the condition below. */
extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
if ((e0 == true_edge && integer_zerop (arg0))
- || (e0 == false_edge && integer_onep (arg0))
+ || (e0 == false_edge && !integer_zerop (arg0))
|| (e1 == true_edge && integer_zerop (arg1))
- || (e1 == false_edge && integer_onep (arg1)))
+ || (e1 == false_edge && !integer_zerop (arg1)))
cond = fold_build1_loc (gimple_location (stmt),
- TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
+ TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
+ if (neg)
+ {
+ cond = fold_convert_loc (gimple_location (stmt),
+ TREE_TYPE (result), cond);
+ cond = fold_build1_loc (gimple_location (stmt),
+ NEGATE_EXPR, TREE_TYPE (cond), cond);
+ }
+
/* Insert our new statements at the end of conditional block before the
COND_STMT. */
gsi = gsi_for_stmt (stmt);
Index: testsuite/gcc.c-torture/execute/20120427-2.c
===================================================================
--- testsuite/gcc.c-torture/execute/20120427-2.c (revisione 0)
+++ testsuite/gcc.c-torture/execute/20120427-2.c (revisione 0)
@@ -0,0 +1,38 @@
+typedef struct sreal
+{
+ unsigned sig; /* Significant. */
+ int exp; /* Exponent. */
+} sreal;
+
+sreal_compare (sreal *a, sreal *b)
+{
+ if (a->exp > b->exp)
+ return 1;
+ if (a->exp < b->exp)
+ return -1;
+ if (a->sig > b->sig)
+ return 1;
+ if (a->sig < b->sig)
+ return -1;
+ return 0;
+}
+
+sreal a[] = {
+ { 0, 0 },
+ { 1, 0 },
+ { 0, 1 },
+ { 1, 1 }
+};
+
+int main()
+{
+ int i, j;
+ for (i = 0; i <= 3; i++) {
+ for (j = 0; j < 3; j++) {
+ if (i < j && sreal_compare(&a[i], &a[j]) != -1) abort();
+ if (i == j && sreal_compare(&a[i], &a[j]) != 0) abort();
+ if (i > j && sreal_compare(&a[i], &a[j]) != 1) abort();
+ }
+ }
+ return 0;
+}
Index: testsuite/gcc.dg/tree-ssa/phi-opt-10.c
===================================================================
--- testsuite/gcc.dg/tree-ssa/phi-opt-10.c (revisione 0)
+++ testsuite/gcc.dg/tree-ssa/phi-opt-10.c (revisione 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+int nem1_phi (unsigned long a) { return a ? -1 : 0; }
+int eqm1_phi (unsigned long a) { return a ? 0 : -1; }
+
+int spaceship1 (long a) { return a > 0 ? 1 : a < 0 ? -1 : 0; }
+int spaceship2 (long a) { return a > 0 ? 1 : a == 0 ? 0 : -1; }
+
+/* { dg-final { scan-tree-dump-times " = -D" 4 "optimized"} } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
