https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67281
Bug ID: 67281
Summary: HTM builtins aren't treated as compiler barriers on
powerpc
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: tuliom at linux dot vnet.ibm.com
Target Milestone: ---
Depending on the level of optimization, GCC moves a memory access outside a
transaction which breaks the atomicity of the transaction.
This is a small testcase that reproduces this behavior:
$ cat tbegin-barrier.c
long
foo (long dest, long src0, long src1, long tries)
{
long i;
for (i = 0; i < tries; i++)
{
__builtin_tbegin (0);
dest = src0 + src1;
__builtin_tend (0);
}
return dest;
}
compiling using: -O2 -S -mcpu=power8 tbegin-barrier.c
gives
foo:
cmpdi 0,6,0
blelr 0
mtctr 6
add 3,4,5
.p2align 4,,15
.L3:
tbegin. 0
tend. 0
bdnz .L3
blr
