[Bug tree-optimization/46029] -ftree-loop-if-convert-stores causes FAIL: libstdc++-v3/testsuite/ext/pb_ds/example/tree_intervals.cc
zsojka at seznam dot cz
gcc-bugzilla@gcc.gnu.org
Fri Oct 15 00:53:00 GMT 2010
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46029
--- Comment #1 from Zdenek Sojka <zsojka at seznam dot cz> 2010-10-15 00:53:15 UTC ---
Created attachment 22048
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22048
hopefully reduced testcase
$ g++ -O -ftree-loop-if-convert-stores pr46029.C
$ ./a.out
Segmentation fault
In the assembly, with -ftree-loop-if-convert-stores, "nd_it.get_l_child
().get_metadata ()" in apply_update() is loaded unconditionally.
62a64
> mov esi, 0 # tmp69,
64,69c66,70
< mov rcx, QWORD PTR [rax] # D.2294, p_nd_32->m_p_left
< mov edx, 0 # l_max_endpoint,
< test rcx, rcx # D.2294
< je .L3 #,
< mov edx, DWORD PTR [rcx+16] # l_max_endpoint, MEM[(unsigned int
&)D.2294_12 + 16]
< .L3:
---
> mov rdx, QWORD PTR [rax] # D.2294, p_nd_32->m_p_left
> mov ecx, DWORD PTR [rdx+16] # l_max_endpoint, MEM[(unsigned int &)D.2294_12 + 16]
> test rdx, rdx # D.2294
> mov edx, esi # l_max_endpoint, tmp69
> cmovne edx, ecx # l_max_endpoint,, l_max_endpoint
In the first case, memory is not accessed if the pointer is NULL, but in the
second, "mov ecx, DWORD PTR [rdx+16]" reads invalid memory.
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