The testcase from the PR at -O2 shows
((_277 == 2) AND (_79 == 0))
OR ((NOT (_277 == 0)) AND (NOT (_277 > 2)) AND (NOT (_277 == 2)) AND (_79
== 0))
OR ((NOT (pretmp_300 == 255)) AND (_277 == 0) AND (NOT (_277 > 2)) AND (NOT
(_277 == 2)) AND (_79 == 0))
which we fail to simplify. The following patch makes us simplify
the relations on _277, producing
((_79 == 0) AND (_277 == 2))
OR ((_79 == 0) AND (_277 <= 1) AND (NOT (_277 == 0)))
OR ((_79 == 0) AND (_277 == 0) AND (NOT (pretmp_300 == 255)))
which might be an incremental step to resolve a bogus uninit
diagnostic at -O2. The patch uses maybe_fold_and_comparison for this.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/107919
* gimple-predicate-analysis.cc (simplify_1): Rename to ...
(simplify_1a): .. this.
(simplify_1b): New.
(predicate::simplify): Call both simplify_1a and simplify_1b.
---
gcc/gimple-predicate-analysis.cc | 83 +++++++++++++++++++++++++++++---
1 file changed, 76 insertions(+), 7 deletions(-)
diff --git a/gcc/gimple-predicate-analysis.cc b/gcc/gimple-predicate-analysis.cc
index 23be4b69bab..ce2e1d10e43 100644
--- a/gcc/gimple-predicate-analysis.cc
+++ b/gcc/gimple-predicate-analysis.cc
@@ -42,6 +42,7 @@
#include "value-query.h"
#include "cfganal.h"
#include "tree-eh.h"
+#include "gimple-fold.h"
#include "gimple-predicate-analysis.h"
@@ -1174,7 +1175,9 @@ compute_control_dep_chain (basic_block dom_bb,
const_basic_block dep_bb,
/* Implemented simplifications:
- 1) ((x IOR y) != 0) AND (x != 0) is equivalent to (x != 0);
+ 1a) ((x IOR y) != 0) AND (x != 0) is equivalent to (x != 0);
+ 1b) [!](X rel y) AND [!](X rel y') where y == y' or both constant
+ can possibly be simplified
2) (X AND Y) OR (!X AND Y) is equivalent to Y;
3) X OR (!X AND Y) is equivalent to (X OR Y);
4) ((x IAND y) != 0) || (x != 0 AND y != 0)) is equivalent to
@@ -1184,11 +1187,11 @@ compute_control_dep_chain (basic_block dom_bb,
const_basic_block dep_bb,
PREDS is the predicate chains, and N is the number of chains. */
-/* Implement rule 1 above. PREDS is the AND predicate to simplify
+/* Implement rule 1a above. PREDS is the AND predicate to simplify
in place. */
static void
-simplify_1 (pred_chain &chain)
+simplify_1a (pred_chain &chain)
{
bool simplified = false;
pred_chain s_chain = vNULL;
@@ -1245,6 +1248,66 @@ simplify_1 (pred_chain &chain)
chain = s_chain;
}
+/* Implement rule 1b above. PREDS is the AND predicate to simplify
+ in place. Returns true if CHAIN simplifies to true. */
+
+static bool
+simplify_1b (pred_chain &chain)
+{
+ for (unsigned i = 0; i < chain.length (); i++)
+ {
+ pred_info &a_pred = chain[i];
+
+ for (unsigned j = i + 1; j < chain.length (); ++j)
+ {
+ pred_info &b_pred = chain[j];
+
+ if (!operand_equal_p (a_pred.pred_lhs, b_pred.pred_lhs)
+ || (!operand_equal_p (a_pred.pred_rhs, b_pred.pred_rhs)
+ && !(CONSTANT_CLASS_P (a_pred.pred_rhs)
+ && CONSTANT_CLASS_P (b_pred.pred_rhs))))
+ continue;
+
+ tree_code a_code = a_pred.cond_code;
+ if (a_pred.invert)
+ a_code = invert_tree_comparison (a_code, false);
+ tree_code b_code = b_pred.cond_code;
+ if (b_pred.invert)
+ b_code = invert_tree_comparison (b_code, false);
+ /* Try to combine X a_code Y && X b_code Y'. */
+ tree comb = maybe_fold_and_comparisons (boolean_type_node,
+ a_code,
+ a_pred.pred_lhs,
+ a_pred.pred_rhs,
+ b_code,
+ b_pred.pred_lhs,
+ b_pred.pred_rhs, NULL);
+ if (!comb)
+ ;
+ else if (integer_zerop (comb))
+ return true;
+ else if (integer_truep (comb))
+ {
+ chain.ordered_remove (j);
+ chain.ordered_remove (i);
+ i--;
+ break;
+ }
+ else if (COMPARISON_CLASS_P (comb)
+ && operand_equal_p (a_pred.pred_lhs, TREE_OPERAND (comb, 0)))
+ {
+ chain.ordered_remove (j);
+ a_pred.cond_code = TREE_CODE (comb);
+ a_pred.pred_rhs = TREE_OPERAND (comb, 1);
+ a_pred.invert = false;
+ j--;
+ }
+ }
+ }
+
+ return false;
+}
+
/* Implements rule 2 for the OR predicate PREDS:
2) (X AND Y) OR (!X AND Y) is equivalent to Y. */
@@ -1435,11 +1498,17 @@ predicate::simplify (gimple *use_or_def, bool is_use)
dump (dump_file, use_or_def, is_use ? "[USE]:\n" : "[DEF]:\n");
}
- unsigned n = m_preds.length ();
- for (unsigned i = 0; i < n; i++)
- ::simplify_1 (m_preds[i]);
+ for (unsigned i = 0; i < m_preds.length (); i++)
+ {
+ ::simplify_1a (m_preds[i]);
+ if (::simplify_1b (m_preds[i]))
+ {
+ m_preds.ordered_remove (i);
+ i--;
+ }
+ }
- if (n < 2)
+ if (m_preds.length () < 2)
return;
bool changed;
--
2.35.3
