From: Richard Biener <rguenther@suse.de>
Date: Wed, 14 Dec 2016 10:31:37 +0000 (+0000)
Subject: re PR tree-optimization/78731 (Possible bug with switch when optimization is turned... 
X-Git-Tag: releases/gcc-5.5.0~639
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f6d10b7071861a388809d35386e673c28feb45e;p=thirdparty%2Fgcc.git

re PR tree-optimization/78731 (Possible bug with switch when optimization is turned on.)

2016-12-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78731
	* tree-ssa-threadedge.c (simplify_control_stmt_condition):
	If we've seen a backedge to not walk the SSA value chain.
	(thread_around_empty_blocks): Pass down whether we've seen
	a backedge to simplify_control_stmt_condition.
	(thread_through_normal_block): Likewise.

	* gcc.dg/torture/pr78731.c: New testcase.

From-SVN: r243641
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 157e40a6efc0..6df670715947 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2016-12-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78731
+	* tree-ssa-threadedge.c (simplify_control_stmt_condition):
+	If we've seen a backedge to not walk the SSA value chain.
+	(thread_around_empty_blocks): Pass down whether we've seen
+	a backedge to simplify_control_stmt_condition.
+	(thread_through_normal_block): Likewise.
+
 2016-12-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fd5f9ecfc979..78ed52518fa8 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-12-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78731
+	* gcc.dg/torture/pr78731.c: New testcase.
+
 2016-12-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/gcc.dg/torture/pr78731.c b/gcc/testsuite/gcc.dg/torture/pr78731.c
new file mode 100644
index 000000000000..5a4d43be1f9b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr78731.c
@@ -0,0 +1,41 @@
+/* { dg-do run } */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define GENERAL 1
+#define BRACKETS 2
+#define QUOTES 3
+
+void __attribute__((noinline,noclone))
+foo(char *qb, char* into)
+{
+  int state = QUOTES;
+  int save_state = BRACKETS;
+
+  while (qb)
+    {
+      switch (state)
+	{
+	case BRACKETS:
+	  exit(0);
+	case GENERAL:
+	  abort ();
+	case QUOTES:
+	  state = save_state;
+	  save_state = GENERAL;
+	  break;
+	default: ;
+	}
+      printf("State %d btw GENERAL %d\n", state, GENERAL);
+    }
+  abort ();
+}
+
+int main()
+{
+  char *b = "123";
+  char out[4];
+  foo(b, out);
+  return 0;
+}
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index 90c1e2af94ac..97e087569aa6 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -574,7 +574,8 @@ simplify_control_stmt_condition (edge e,
 				 gimple stmt,
 				 gcond *dummy_cond,
 				 tree (*simplify) (gimple, gimple),
-				 bool handle_dominating_asserts)
+				 bool handle_dominating_asserts,
+				 bool backedge_seen)
 {
   tree cond, cached_lhs;
   enum gimple_code code = gimple_code (stmt);
@@ -593,7 +594,7 @@ simplify_control_stmt_condition (edge e,
       /* Get the current value of both operands.  */
       if (TREE_CODE (op0) == SSA_NAME)
 	{
-	  for (int i = 0; i < 2; i++)
+	  for (int i = 0; i < (backedge_seen ? 1 : 2); i++)
 	    {
 	      if (TREE_CODE (op0) == SSA_NAME
 		  && SSA_NAME_VALUE (op0))
@@ -605,7 +606,7 @@ simplify_control_stmt_condition (edge e,
 
       if (TREE_CODE (op1) == SSA_NAME)
 	{
-	  for (int i = 0; i < 2; i++)
+	  for (int i = 0; i < (backedge_seen ? 1 : 2); i++)
 	    {
 	      if (TREE_CODE (op1) == SSA_NAME
 		  && SSA_NAME_VALUE (op1))
@@ -689,7 +690,7 @@ simplify_control_stmt_condition (edge e,
 	 a loop invariant SSA_NAME used in the condition.  */
       if (cached_lhs)
 	{
-	  for (int i = 0; i < 2; i++)
+	  for (int i = 0; i < (backedge_seen ? 1 : 2); i++)
 	    {
 	      if (TREE_CODE (cached_lhs) == SSA_NAME
 		  && SSA_NAME_VALUE (cached_lhs))
@@ -940,7 +941,8 @@ thread_around_empty_blocks (edge taken_edge,
 
   /* Extract and simplify the condition.  */
   cond = simplify_control_stmt_condition (taken_edge, stmt, dummy_cond,
-					  simplify, handle_dominating_asserts);
+					  simplify, handle_dominating_asserts,
+					  *backedge_seen_p);
 
   /* If the condition can be statically computed and we have not already
      visited the destination edge, then add the taken edge to our thread
@@ -1326,7 +1328,8 @@ thread_through_normal_block (edge e,
 
       /* Extract and simplify the condition.  */
       cond = simplify_control_stmt_condition (e, stmt, dummy_cond, simplify,
-					      handle_dominating_asserts);
+					      handle_dominating_asserts,
+					      *backedge_seen_p);
 
       if (!cond)
 	return 0;