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tree-optimization/105431 - another overflow in powi handling

Message ID 20220429091015.62A1E13446@imap2.suse-dmz.suse.de
State Committed
Commit 44b09adb9bad99dd7e3017c5ecefed7f7c9a1590
Headers
Series tree-optimization/105431 - another overflow in powi handling |

Commit Message

Richard Biener April 29, 2022, 9:10 a.m. UTC 
  This avoids undefined signed overflow when calling powi_as_mults_1.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2022-04-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105431
	* tree-ssa-math-opts.cc (powi_as_mults_1): Make n unsigned.
	(powi_as_mults): Use absu_hwi.
	(gimple_expand_builtin_powi): Remove now pointless n != -n
	check.
---
 gcc/tree-ssa-math-opts.cc | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)
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Patch

diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index 7555793948e..232e903b0d2 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -1495,7 +1495,7 @@  powi_cost (HOST_WIDE_INT n)
 
 static tree
 powi_as_mults_1 (gimple_stmt_iterator *gsi, location_t loc, tree type,
-		 HOST_WIDE_INT n, tree *cache)
+		 unsigned HOST_WIDE_INT n, tree *cache)
 {
   tree op0, op1, ssa_target;
   unsigned HOST_WIDE_INT digit;
@@ -1548,7 +1548,7 @@  powi_as_mults (gimple_stmt_iterator *gsi, location_t loc,
   memset (cache, 0, sizeof (cache));
   cache[1] = arg0;
 
-  result = powi_as_mults_1 (gsi, loc, type, (n < 0) ? -n : n, cache);
+  result = powi_as_mults_1 (gsi, loc, type, absu_hwi (n), cache);
   if (n >= 0)
     return result;
 
@@ -1572,11 +1572,9 @@  static tree
 gimple_expand_builtin_powi (gimple_stmt_iterator *gsi, location_t loc, 
 			    tree arg0, HOST_WIDE_INT n)
 {
-  /* Avoid largest negative number.  */
-  if (n != -n
-      && ((n >= -1 && n <= 2)
-	  || (optimize_function_for_speed_p (cfun)
-	      && powi_cost (n) <= POWI_MAX_MULTS)))
+  if ((n >= -1 && n <= 2)
+      || (optimize_function_for_speed_p (cfun)
+	  && powi_cost (n) <= POWI_MAX_MULTS))
     return powi_as_mults (gsi, loc, arg0, n);
 
   return NULL_TREE;