[nvptx] Add uniform_warp_check insn
On a GT 1030, with driver version 470.94 and -mptx=3.1 I run into:
...
FAIL: libgomp.oacc-c/../libgomp.oacc-c-c++-common/parallel-dims.c \
-DACC_DEVICE_TYPE_nvidia=1 -DACC_MEM_SHARED=0 -foffload=nvptx-none \
-O2 execution test
...
which minimizes to the same test-case as listed in commit "[nvptx]
Update default ptx isa to 6.3".
The problem is again that the first diverging branch is not handled as such in
SASS, which causes problems with a subsequent shfl insn, but given that we
have -mptx=3.1 we can't use the bar.warp.sync insn.
Given that the default is now -mptx=6.3, and consequently -mptx=3.1 is of a
lesser importance, implement the next best thing: abort when detecting
non-convergence using this insn:
...
{ .reg.b32 act;
vote.ballot.b32 act,1;
.reg.pred uni;
setp.eq.b32 uni,act,0xffffffff;
@ !uni trap;
@ !uni exit;
}
...
Interestingly, the effect of this is that rather than aborting, the test-case
now passes.
Tested on x86_64 with nvptx accelerator.
gcc/ChangeLog:
2022-01-31 Tom de Vries <tdevries@suse.de>
* config/nvptx/nvptx.cc (nvptx_single): Use nvptx_uniform_warp_check.
* config/nvptx/nvptx.md (define_c_enum "unspecv"): Add
UNSPECV_UNIFORM_WARP_CHECK.
(define_insn "nvptx_uniform_warp_check"): New define_insn.