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* [PATCH v2 1/2] strlen: fold strstr() even if the length isn't previously known [PR96601]
@ 2023-09-04 20:58 Hamza Mahfooz
  2023-09-04 20:58 ` [PATCH v2 2/2] strlen: call handle_builtin_strlen() from fold_strstr_to_strncmp() Hamza Mahfooz
  2023-09-05  5:14 ` [PATCH v2 1/2] strlen: fold strstr() even if the length isn't previously known [PR96601] Jeff Law
  0 siblings, 2 replies; 5+ messages in thread
From: Hamza Mahfooz @ 2023-09-04 20:58 UTC (permalink / raw)
  To: gcc-patches
  Cc: Jeff Law, Richard Biener, Jakub Jelinek, Ian Lance Taylor,
	Prathamesh Kulkarni, Aldy Hernandez, Martin Sebor, Hamza Mahfooz

Currently, we give up in fold_strstr_to_strncmp() if the length of the
the second argument to strstr() isn't known to us by the time we hit
that function. However, we can instead insert a strlen() in ourselves
and continue trying to fold strstr() into strlen()+strncmp().

	PR tree-optimization/96601

gcc/ChangeLog:

	* tree-ssa-strlen.cc (fold_strstr_to_strncmp): If arg1_len == NULL,
	insert a strlen() for strstr()'s arg1 and use it as arg1_len.

gcc/testsuite/ChangeLog:

	* gcc.dg/strlenopt-30.c: Modify test.

Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
Please push this for me if you think it looks good. Since, I don't have
write access to the repository.
---
 gcc/testsuite/gcc.dg/strlenopt-30.c |  5 +-
 gcc/tree-ssa-strlen.cc              | 81 ++++++++++++++++-------------
 2 files changed, 45 insertions(+), 41 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/strlenopt-30.c b/gcc/testsuite/gcc.dg/strlenopt-30.c
index 2a3098ba96f..1ee814048c1 100644
--- a/gcc/testsuite/gcc.dg/strlenopt-30.c
+++ b/gcc/testsuite/gcc.dg/strlenopt-30.c
@@ -38,9 +38,6 @@ void f5(char *s)
     foo_f5();
 }
 
-/* Do not perform transform, since strlen (t)
-   is unknown.  */
-
 __attribute__((no_icf))
 _Bool f6(char *s, char *t)
 {
@@ -60,4 +57,4 @@ _Bool f7(char *s)
   return (t1 == s);
 }
 
-/* { dg-final { scan-tree-dump-times "__builtin_strncmp" 5 "strlen1" } } */
+/* { dg-final { scan-tree-dump-times "__builtin_strncmp" 6 "strlen1" } } */
diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
index 8b7ef919826..b0ebbb0db62 100644
--- a/gcc/tree-ssa-strlen.cc
+++ b/gcc/tree-ssa-strlen.cc
@@ -5273,6 +5273,7 @@ fold_strstr_to_strncmp (tree rhs1, tree rhs2, gimple *stmt)
 	  tree arg1 = gimple_call_arg (call_stmt, 1);
 	  tree arg1_len = NULL_TREE;
 	  int idx = get_stridx (arg1, call_stmt);
+	  gimple_stmt_iterator gsi = gsi_for_stmt (call_stmt);
 
 	  if (idx)
 	    {
@@ -5286,51 +5287,57 @@ fold_strstr_to_strncmp (tree rhs1, tree rhs2, gimple *stmt)
 		}
 	    }
 
-	  if (arg1_len != NULL_TREE)
+	  if (arg1_len == NULL_TREE)
 	    {
-	      gimple_stmt_iterator gsi = gsi_for_stmt (call_stmt);
-	      tree strncmp_decl = builtin_decl_explicit (BUILT_IN_STRNCMP);
+	      tree strlen_decl = builtin_decl_explicit (BUILT_IN_STRLEN);
+	      gcall *strlen_call = gimple_build_call (strlen_decl, 1, arg1);
+	      tree strlen_lhs = make_ssa_name (size_type_node, strlen_call);
+
+	      gimple_call_set_lhs (strlen_call, strlen_lhs);
+	      gimple_set_vuse (strlen_call, gimple_vuse (call_stmt));
+	      gsi_insert_before (&gsi, strlen_call, GSI_SAME_STMT);
+	      arg1_len = strlen_lhs;
+	    }
+	  else if (!is_gimple_val (arg1_len))
+	    {
+	      tree arg1_len_tmp = make_ssa_name (TREE_TYPE (arg1_len));
+	      gassign *arg1_stmt = gimple_build_assign (arg1_len_tmp,
+							arg1_len);
+	      gsi_insert_before (&gsi, arg1_stmt, GSI_SAME_STMT);
+	      arg1_len = arg1_len_tmp;
+	    }
 
-	      if (!is_gimple_val (arg1_len))
+	  tree strncmp_decl = builtin_decl_explicit (BUILT_IN_STRNCMP);
+	  gcall *strncmp_call = gimple_build_call (strncmp_decl, 3,
+						   arg0, arg1, arg1_len);
+	  tree strncmp_lhs = make_ssa_name (integer_type_node);
+	  gimple_set_vuse (strncmp_call, gimple_vuse (call_stmt));
+	  gimple_call_set_lhs (strncmp_call, strncmp_lhs);
+	  gsi_remove (&gsi, true);
+	  gsi_insert_before (&gsi, strncmp_call, GSI_SAME_STMT);
+	  tree zero = build_zero_cst (TREE_TYPE (strncmp_lhs));
+
+	  if (is_gimple_assign (stmt))
+	    {
+	      if (gimple_assign_rhs_code (stmt) == COND_EXPR)
 		{
-		  tree arg1_len_tmp = make_ssa_name (TREE_TYPE (arg1_len));
-		  gassign *arg1_stmt = gimple_build_assign (arg1_len_tmp,
-							    arg1_len);
-		  gsi_insert_before (&gsi, arg1_stmt, GSI_SAME_STMT);
-		  arg1_len = arg1_len_tmp;
-		}
-
-	      gcall *strncmp_call = gimple_build_call (strncmp_decl, 3,
-						      arg0, arg1, arg1_len);
-	      tree strncmp_lhs = make_ssa_name (integer_type_node);
-	      gimple_set_vuse (strncmp_call, gimple_vuse (call_stmt));
-	      gimple_call_set_lhs (strncmp_call, strncmp_lhs);
-	      gsi_remove (&gsi, true);
-	      gsi_insert_before (&gsi, strncmp_call, GSI_SAME_STMT);
-	      tree zero = build_zero_cst (TREE_TYPE (strncmp_lhs));
-
-	      if (is_gimple_assign (stmt))
-		{
-		  if (gimple_assign_rhs_code (stmt) == COND_EXPR)
-		    {
-		      tree cond = gimple_assign_rhs1 (stmt);
-		      TREE_OPERAND (cond, 0) = strncmp_lhs;
-		      TREE_OPERAND (cond, 1) = zero;
-		    }
-		  else
-		    {
-		      gimple_assign_set_rhs1 (stmt, strncmp_lhs);
-		      gimple_assign_set_rhs2 (stmt, zero);
-		    }
+		  tree cond = gimple_assign_rhs1 (stmt);
+		  TREE_OPERAND (cond, 0) = strncmp_lhs;
+		  TREE_OPERAND (cond, 1) = zero;
 		}
 	      else
 		{
-		  gcond *cond = as_a<gcond *> (stmt);
-		  gimple_cond_set_lhs (cond, strncmp_lhs);
-		  gimple_cond_set_rhs (cond, zero);
+		  gimple_assign_set_rhs1 (stmt, strncmp_lhs);
+		  gimple_assign_set_rhs2 (stmt, zero);
 		}
-	      update_stmt (stmt);
 	    }
+	  else
+	    {
+	      gcond *cond = as_a<gcond *> (stmt);
+	      gimple_cond_set_lhs (cond, strncmp_lhs);
+	      gimple_cond_set_rhs (cond, zero);
+	    }
+	  update_stmt (stmt);
 	}
     }
 }
-- 
2.42.0


^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-09-06  4:15 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-09-04 20:58 [PATCH v2 1/2] strlen: fold strstr() even if the length isn't previously known [PR96601] Hamza Mahfooz
2023-09-04 20:58 ` [PATCH v2 2/2] strlen: call handle_builtin_strlen() from fold_strstr_to_strncmp() Hamza Mahfooz
2023-09-05  5:14 ` [PATCH v2 1/2] strlen: fold strstr() even if the length isn't previously known [PR96601] Jeff Law
2023-09-05  9:04   ` Jakub Jelinek
2023-09-06  4:15   ` Hamza Mahfooz

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