Added testcase. Here is the new patch:
2014-11-12 <tejohn...@google.com>
gcc:
PR tree-optimization/63841
* tree.c (initializer_zerop): A constructor with no elements
does not zero initialize.
gcc/testsuite:
* g++.dg/tree-ssa/pr63841.C: New test.
Index: tree.c
===================================================================
--- tree.c (revision 217190)
+++ tree.c (working copy)
@@ -10330,6 +10330,8 @@ initializer_zerop (const_tree init)
{
unsigned HOST_WIDE_INT idx;
+ if (!CONSTRUCTOR_NELTS (init))
+ return false;
FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (init), idx, elt)
if (!initializer_zerop (elt))
return false;
Index: testsuite/g++.dg/tree-ssa/pr63841.C
===================================================================
--- testsuite/g++.dg/tree-ssa/pr63841.C (revision 0)
+++ testsuite/g++.dg/tree-ssa/pr63841.C (working copy)
@@ -0,0 +1,38 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <cstdio>
+#include <string>
+
+std::string __attribute__ ((noinline)) comp_test_write() {
+ std::string data;
+
+ for (int i = 0; i < 2; ++i) {
+ char b = 1 >> (i * 8);
+ data.append(&b, 1);
+ }
+
+ return data;
+}
+
+std::string __attribute__ ((noinline)) comp_test_write_good() {
+ std::string data;
+
+ char b;
+ for (int i = 0; i < 2; ++i) {
+ b = 1 >> (i * 8);
+ data.append(&b, 1);
+ }
+
+ return data;
+}
+
+int main() {
+ std::string good = comp_test_write_good();
+ printf("expected: %hx\n", *(short*)good.c_str());
+
+ std::string bad = comp_test_write();
+ printf("got: %hx\n", *(short*)bad.c_str());
+
+ return good != bad;
+}
On Wed, Nov 12, 2014 at 2:17 PM, Xinliang David Li <davi...@google.com> wrote:
> missing test case?
>
> David
>
> On Wed, Nov 12, 2014 at 2:13 PM, Teresa Johnson <tejohn...@google.com> wrote:
>> This patch fixes an issue where tree-strlen was incorrectly removing a
>> store of 0 into a string because it thought a prior CLOBBER (which is
>> an empty constructor with no elements) was zero-initializing the
>> string.
>>
>> Bootstrapped and tested on x86_64-unknown-linux-gnu. OK for trunk?
>>
>> Thanks,
>> Teresa
>>
>> 2014-11-12 <tejohn...@google.com>
>>
>> PR tree-optimization/63841
>> * tree.c (initializer_zerop): A constructor with no elements
>> does not zero initialize.
>>
>> Index: tree.c
>> ===================================================================
>> --- tree.c (revision 217190)
>> +++ tree.c (working copy)
>> @@ -10330,6 +10330,8 @@ initializer_zerop (const_tree init)
>> {
>> unsigned HOST_WIDE_INT idx;
>>
>> + if (!CONSTRUCTOR_NELTS (init))
>> + return false;
>> FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (init), idx, elt)
>> if (!initializer_zerop (elt))
>> return false;
>>
>>
>> --
>> Teresa Johnson | Software Engineer | tejohn...@google.com | 408-460-2413
--
Teresa Johnson | Software Engineer | tejohn...@google.com | 408-460-2413
