https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64689
Bug ID: 64689
Summary: tree-vectorize generates wrong code with inlined
function - minimum working example included
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: philipp.gschwandtner at uibk dot ac.at
Created attachment 34500
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34500&action=edit
minimum working example
The tree vectorizer in gcc 4.7-4.9 appears to generate semantically incorrect
code for the particular case clarified in the attached minimum working example.
gcc 4.6.3 does not show this issue. In gcc 4.7.3 only one of the checks fails,
in gcc 4.8.3 and 4.9.2 both of them fail (as these versions also seem to
recognize case A as vectorizable).
Testing was performed on an Intel Xeon E5-2699 v3 Haswell CPU running a
3.10.0-123.13.1.el7.x86_64 Linux kernel.
Compile with:
gcc test.c -o test -O3 -std=c99 -pedantic -Wall -Wextra -fwrapv
-fno-strict-aliasing
Expected output (equals gcc 4.6.3 output):
Checking case A:
EQUAL!
Checking case B:
EQUAL!
Actual output (for gcc 4.8.3 and 4.9.2):
Checking case A:
NOT EQUAL!
C1:
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
C2:
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
Checking case B:
NOT EQUAL!
C1:
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
-2 0i, -2 0i, -2 0i, -2 0i,
C2:
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
-1 0i, -1 0i, -1 0i, -1 0i,
Above output is produced when compiled with gcc 4.9.2 and 4.8.3. For gcc 4.7.3
the check for case A succeeds while the check for case B still fails.
