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Re: [PATCH] Fix infinite recursion with div-by-zero (PR middle-end/70992)


On Thu, Jul 20, 2017 at 08:22:59PM +0200, Richard Biener wrote:
> No, we shouldn't.  Maybe trapping ops shouldn't be marked TREE_CONSTANT?
> (Make sure to test with Ada...)

That works for both testcases, but I can't say I really like the idea of
modifying build2... but it's where the TREE_CONSTANT comes from.

The tree_could_trap_p bit is because the C++ FE can pass "< x" around, e.g.
a LT_EXPR with the first operand null.

Bootstrapped/regtested on x86_64-linux (Ada included) and powerpc64le-unknown-linux-gnu,
ok for trunk?

2017-07-25  Marek Polacek  <polacek@redhat.com>

	PR c/70992
	* tree-eh.c (tree_could_trap_p): Check if the first operand is null.
	* tree.c: Include "tree-eh.h".
	(build2_stat): Only set TREE_CONSTANT if the tree couldn't trap.

	* gcc.dg/overflow-warn-1.c: Adjust dg-error.
	* gcc.dg/overflow-warn-2.c: Likewise.
	* gcc.dg/overflow-warn-3.c: Likewise.
	* gcc.dg/overflow-warn-4.c: Likewise.
	* gcc.dg/torture/pr70992-2.c: New test.
	* gcc.dg/torture/pr70992.c: New test.

diff --git gcc/testsuite/gcc.dg/overflow-warn-1.c gcc/testsuite/gcc.dg/overflow-warn-1.c
index 8eb322579cf..a5cd5738636 100644
--- gcc/testsuite/gcc.dg/overflow-warn-1.c
+++ gcc/testsuite/gcc.dg/overflow-warn-1.c
@@ -49,7 +49,7 @@ static int sc = INT_MAX + 1; /* { dg-warning "25:integer overflow in expression"
 void *p = 0 * (INT_MAX + 1); /* { dg-warning "integer overflow in expression" } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-1 } */
 void *q = 0 * (1 / 0); /* { dg-warning "division by zero" } */
-/* { dg-error "initializer element is not computable at load time" "constant" { target *-*-* } .-1 } */
+/* { dg-error "initializer element is not constant" "constant" { target *-*-* } .-1 } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *r = (1 ? 0 : INT_MAX+1);
 
diff --git gcc/testsuite/gcc.dg/overflow-warn-2.c gcc/testsuite/gcc.dg/overflow-warn-2.c
index f048d6dae2a..05ab104fa4a 100644
--- gcc/testsuite/gcc.dg/overflow-warn-2.c
+++ gcc/testsuite/gcc.dg/overflow-warn-2.c
@@ -49,7 +49,7 @@ static int sc = INT_MAX + 1; /* { dg-warning "integer overflow in expression" }
 void *p = 0 * (INT_MAX + 1); /* { dg-warning "integer overflow in expression" } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-1 } */
 void *q = 0 * (1 / 0); /* { dg-warning "division by zero" } */
-/* { dg-error "initializer element is not computable at load time" "constant" { target *-*-* } .-1 } */
+/* { dg-error "initializer element is not constant" "constant" { target *-*-* } .-1 } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *r = (1 ? 0 : INT_MAX+1);
 
diff --git gcc/testsuite/gcc.dg/overflow-warn-3.c gcc/testsuite/gcc.dg/overflow-warn-3.c
index 664011e401d..fd4a34f67e2 100644
--- gcc/testsuite/gcc.dg/overflow-warn-3.c
+++ gcc/testsuite/gcc.dg/overflow-warn-3.c
@@ -55,7 +55,7 @@ void *p = 0 * (INT_MAX + 1); /* { dg-warning "integer overflow in expression" }
 /* { dg-warning "overflow in constant expression" "constant" { target *-*-* } .-1 } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *q = 0 * (1 / 0); /* { dg-warning "division by zero" } */
-/* { dg-error "initializer element is not computable at load time" "constant" { target *-*-* } .-1 } */
+/* { dg-error "initializer element is not constant" "constant" { target *-*-* } .-1 } */
 /* { dg-warning "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *r = (1 ? 0 : INT_MAX+1);
 
diff --git gcc/testsuite/gcc.dg/overflow-warn-4.c gcc/testsuite/gcc.dg/overflow-warn-4.c
index 52677ce897a..018e3e1e4cd 100644
--- gcc/testsuite/gcc.dg/overflow-warn-4.c
+++ gcc/testsuite/gcc.dg/overflow-warn-4.c
@@ -55,7 +55,7 @@ void *p = 0 * (INT_MAX + 1); /* { dg-warning "integer overflow in expression" }
 /* { dg-error "overflow in constant expression" "constant" { target *-*-* } .-1 } */
 /* { dg-error "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *q = 0 * (1 / 0); /* { dg-warning "division by zero" } */
-/* { dg-error "initializer element is not computable at load time" "constant" { target *-*-* } .-1 } */
+/* { dg-error "initializer element is not constant" "constant" { target *-*-* } .-1 } */
 /* { dg-error "initialization makes pointer from integer without a cast" "null" { target *-*-* } .-2 } */
 void *r = (1 ? 0 : INT_MAX+1);
 
diff --git gcc/testsuite/gcc.dg/torture/pr70992-2.c gcc/testsuite/gcc.dg/torture/pr70992-2.c
index e69de29bb2d..c5d2c5f2683 100644
--- gcc/testsuite/gcc.dg/torture/pr70992-2.c
+++ gcc/testsuite/gcc.dg/torture/pr70992-2.c
@@ -0,0 +1,9 @@
+/* PR middle-end/70992 */
+/* { dg-do compile } */
+
+unsigned int *od;
+int
+fn (void)
+{
+  return (0 % 0 + 1) * *od * 2; /* { dg-warning "division by zero" } */
+}
diff --git gcc/testsuite/gcc.dg/torture/pr70992.c gcc/testsuite/gcc.dg/torture/pr70992.c
index e69de29bb2d..56728e09d1b 100644
--- gcc/testsuite/gcc.dg/torture/pr70992.c
+++ gcc/testsuite/gcc.dg/torture/pr70992.c
@@ -0,0 +1,41 @@
+/* PR middle-end/70992 */
+/* { dg-do compile } */
+
+typedef unsigned int uint32_t;
+typedef int int32_t;
+
+uint32_t
+fn (uint32_t so)
+{
+  return (so + so) * (0x80000000 / 0 + 1); /* { dg-warning "division by zero" } */
+}
+
+uint32_t
+fn5 (uint32_t so)
+{
+  return (0x80000000 / 0 + 1) * (so + so); /* { dg-warning "division by zero" } */
+}
+
+uint32_t
+fn6 (uint32_t so)
+{
+  return (0x80000000 / 0 - 1) * (so + so); /* { dg-warning "division by zero" } */
+}
+
+uint32_t
+fn2 (uint32_t so)
+{
+  return (so + so) * (0x80000000 / 0 - 1); /* { dg-warning "division by zero" } */
+}
+
+int32_t
+fn3 (int32_t so)
+{
+  return (so + so) * (0x80000000 / 0 + 1); /* { dg-warning "division by zero" } */
+}
+
+int32_t
+fn4 (int32_t so)
+{
+  return (so + so) * (0x80000000 / 0 - 1); /* { dg-warning "division by zero" } */
+}
diff --git gcc/tree-eh.c gcc/tree-eh.c
index c68d71a5e54..cde4ef3f387 100644
--- gcc/tree-eh.c
+++ gcc/tree-eh.c
@@ -2599,7 +2599,7 @@ tree_could_trap_p (tree expr)
 
   if (t)
     {
-      if (COMPARISON_CLASS_P (expr))
+      if (COMPARISON_CLASS_P (expr) && TREE_OPERAND (expr, 0))
 	fp_operation = FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 0)));
       else
 	fp_operation = FLOAT_TYPE_P (t);
diff --git gcc/tree.c gcc/tree.c
index b7de2840ac6..205ba7fd79d 100644
--- gcc/tree.c
+++ gcc/tree.c
@@ -62,6 +62,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "print-tree.h"
 #include "ipa-utils.h"
 #include "selftest.h"
+#include "tree-eh.h"
 
 /* Tree code classes.  */
 
@@ -4505,7 +4506,7 @@ build2_stat (enum tree_code code, tree tt, tree arg0, tree arg1 MEM_STAT_DECL)
   else
     {
       TREE_READONLY (t) = read_only;
-      TREE_CONSTANT (t) = constant;
+      TREE_CONSTANT (t) = constant && !tree_could_trap_p (t);
       TREE_THIS_VOLATILE (t)
 	= (TREE_CODE_CLASS (code) == tcc_reference
 	   && arg0 && TREE_THIS_VOLATILE (arg0));

	Marek


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