From: Aldy Hernandez <aldyh@gcc.gnu.org>
Date: Fri, 13 Apr 2018 09:24:58 +0000 (+0000)
Subject: Rewrite size_must_be_zero_p with irange infrastructure.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0bcfd10047731bea91d5a7709d10d8e9177c3826;p=thirdparty%2Fgcc.git

Rewrite size_must_be_zero_p with irange infrastructure.

Rewrite size_must_be_zero_p with irange infrastructure.  Previous
implementation did not get the bits in [7fff,ffff].  This fixes a
handful of regressions.

From-SVN: r259370
---

diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 521bd75fcd8a..af957ce05a2f 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -642,9 +642,25 @@ var_decl_component_p (tree var)
 static bool
 size_must_be_zero_p (tree size)
 {
-  return (integer_zerop (size)
-	  || (TREE_CODE (size) == SSA_NAME
-	      && irange (size).zero_p ()));
+  if (integer_zerop (size))
+    return true;
+
+  if (TREE_CODE (size) != SSA_NAME)
+    return false;
+
+  tree type = TREE_TYPE (size);
+  int prec = TYPE_PRECISION (type);
+
+  wide_int wone = wi::one (prec);
+
+  /* Compute the value of SSIZE_MAX, the largest positive value that
+     can be stored in ssize_t, the signed counterpart of size_t.  */
+  wide_int ssize_max = wi::lshift (wi::one (prec), prec - 1) - 1;
+
+  irange not_zero (type, wone, ssize_max);
+  irange size_range (size);
+  return (size_range.contains_p (0)
+	  && size_range.intersect (not_zero).empty_p ());
 }
 
 /* Fold function call to builtin mem{{,p}cpy,move}.  Try to detect and