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[COMMITTED] PR tree-optimization/103079 - Treat undefined operands as varying in GORI.

Message ID 6633332e-d379-99fd-f98b-83b9b52bd003@redhat.com
State Committed
Headers show
Series [COMMITTED] PR tree-optimization/103079 - Treat undefined operands as varying in GORI. | expand

Commit Message

Andrew MacLeod Nov. 4, 2021, 5:27 p.m. UTC
Outgoing range calculations were assuming an undefined operand produces 
an undefined result.  This is not true, as in the testcxase:

   [0, 0]  = UNDEFINED | b_9     tells us that b_9 is [0,0] and the rest 
of the time, we only know its varying.    Returning UNDEFINED for b_9 is 
clearly wrong.

This patch turns any UNDEFINED values for op1 and op2 into VARYING, and 
then invokes the calcualtion, so instead, we';ll know see:

  [0, 0] = VARYING | b_9   which the solvers will correctly pick the 
right range.

Furthermore, we were always returning UNDEFINED when the LHS is 
undefined... ie.

UNDEFINED = 1 | b_9   was returning UNDEFINED for b_9...  even tho the 
LHS is undefined, it seems to be asking for trouble to continue 
calculating an outgoing range for b_9, so instead we just stop looking now.

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  Pushed.

Andrew
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Patch

commit 004afb984beb6efbe25f44a5857b1c27ebc2ec82
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Thu Nov 4 11:07:28 2021 -0400

    Treat undefined operands as varying in GORI.
    
    If the LHS is UNDEFINED simply stop calculating.  Treat op1 and op2
    as VARYING if they are UNDEFINED.
    
            PR tree-optimization/103079
            gcc/
            * gimple-range-gori.cc (gimple_range_calc_op1): Treat undefined as
            varying.
            (gimple_range_calc_op2): Ditto.
    
            gcc/testsuite/
            * gcc.dg/pr103079.c: New.

diff --git a/gcc/gimple-range-gori.cc b/gcc/gimple-range-gori.cc
index 4e45c593871..2e58c23216b 100644
--- a/gcc/gimple-range-gori.cc
+++ b/gcc/gimple-range-gori.cc
@@ -37,16 +37,13 @@  bool
 gimple_range_calc_op1 (irange &r, const gimple *stmt, const irange &lhs_range)
 {
   gcc_checking_assert (gimple_num_ops (stmt) < 3);
-
-  // An empty range is viral.
-  tree type = TREE_TYPE (gimple_range_operand1 (stmt));
+  // Give up on empty ranges.
   if (lhs_range.undefined_p ())
-    {
-      r.set_undefined ();
-      return true;
-    }
+    return false;
+
   // Unary operations require the type of the first operand in the
   // second range position.
+  tree type = TREE_TYPE (gimple_range_operand1 (stmt));
   int_range<2> type_range (type);
   return gimple_range_handler (stmt)->op1_range (r, type, lhs_range,
 						 type_range);
@@ -61,15 +58,23 @@  bool
 gimple_range_calc_op1 (irange &r, const gimple *stmt,
 		       const irange &lhs_range, const irange &op2_range)
 {
+  // Give up on empty ranges.
+  if (lhs_range.undefined_p ())
+    return false;
+
   // Unary operation are allowed to pass a range in for second operand
   // as there are often additional restrictions beyond the type which
   // can be imposed.  See operator_cast::op1_range().
   tree type = TREE_TYPE (gimple_range_operand1 (stmt));
-  // An empty range is viral.
-  if (op2_range.undefined_p () || lhs_range.undefined_p ())
+  // If op2 is undefined, solve as if it is varying.
+  if (op2_range.undefined_p ())
     {
-      r.set_undefined ();
-      return true;
+      // This is sometimes invoked on single operand stmts.
+      if (gimple_num_ops (stmt) < 3)
+	return false;
+      int_range<2> trange (TREE_TYPE (gimple_range_operand2 (stmt)));
+      return gimple_range_handler (stmt)->op1_range (r, type, lhs_range,
+						     trange);
     }
   return gimple_range_handler (stmt)->op1_range (r, type, lhs_range,
 						 op2_range);
@@ -84,12 +89,17 @@  bool
 gimple_range_calc_op2 (irange &r, const gimple *stmt,
 		       const irange &lhs_range, const irange &op1_range)
 {
+  // Give up on empty ranges.
+  if (lhs_range.undefined_p ())
+    return false;
+
   tree type = TREE_TYPE (gimple_range_operand2 (stmt));
-  // An empty range is viral.
-  if (op1_range.undefined_p () || lhs_range.undefined_p ())
+  // If op1 is undefined, solve as if it is varying.
+  if (op1_range.undefined_p ())
     {
-      r.set_undefined ();
-      return true;
+      int_range<2> trange (TREE_TYPE (gimple_range_operand1 (stmt)));
+      return gimple_range_handler (stmt)->op2_range (r, type, lhs_range,
+						     trange);
     }
   return gimple_range_handler (stmt)->op2_range (r, type, lhs_range,
 						 op1_range);
diff --git a/gcc/testsuite/gcc.dg/pr103079.c b/gcc/testsuite/gcc.dg/pr103079.c
new file mode 100644
index 00000000000..7f6632fc669
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr103079.c
@@ -0,0 +1,20 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Os -fdump-tree-vrp2" } */
+
+int a, b = -2;
+int main() {
+  int d = 0;
+  int t;
+  if (b)
+    goto t1;
+  if (t) {
+t1:
+    if (!a)
+      d = b;
+    while (d > -1)
+      ;
+  }
+  return 0;
+}
+/* { dg-final { scan-tree-dump "PHI" "vrp2" } } */
+