https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61346
Bug ID: 61346
Summary: VRP chooses bad bounds for variable
Product: gcc
Version: 4.10.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ian at airs dot com
CC: cmang at google dot com
The attached file, which is a Go test case converted to C code, should compile
and run without error. It works with GCC 4.6.3 and GCC 4.9 branch with and
without optimization. It works with mainline with -O0 and -O1. It fails with
mainline with -O2.
I think the problem is in the VRP pass. I see this in 067.vrp1:
i_3: [data$len_58, 9223372036854775806] EQUIVALENCES: { i_65 } (1 elements)
This is flat out wrong, as inspection of 066.mergephi2 shows that the ideally
correct range of i_3 should be something like [0, data$len_58]. What's
particularly odd is that i_3 is even set to i_1, and the range of i_1 is
VARYING.
