i386, fab: Optimize __atomic_{add,sub,and,or,xor}_fetch (x, y, z) {==,!=,<,<=,>,>=} 0 [PR98737]

On Wed, Jan 27, 2021 at 12:27:13PM +0100, Ulrich Drepper via Gcc-patches wrote:
> On 1/27/21 11:37 AM, Jakub Jelinek wrote:
> > Would equality comparison against 0 handle the most common cases.
> >
> > The user can write it as
> > __atomic_sub_fetch (x, y, z) == 0
> > or
> > __atomic_fetch_sub (x, y, z) - y == 0
> > thouch, so the expansion code would need to be able to cope with both.
>
> Please also keep !=0, <0, <=0, >0, and >=0 in mind.  They all can be
> useful and can be handled with the flags.

<= 0 and > 0 don't really work well with lock {add,sub,inc,dec}, x86 doesn't
have comparisons that would look solely at both SF and ZF and not at other
flags (and emitting two separate conditional jumps or two setcc insns and
oring them together looks awful).

But the rest can work.

Here is a patch that adds internal functions and optabs for these,
recognizes them at the same spot as e.g. .ATOMIC_BIT_TEST_AND* internal
functions (fold all builtins pass) and expands them appropriately (or for
the <= 0 and > 0 cases of +/- FAILs and let's middle-end fall back).

So far I have handled just the op_fetch builtins, IMHO instead of handling
also __atomic_fetch_sub (x, y, z) - y == 0 etc. we should canonicalize
__atomic_fetch_sub (x, y, z) - y to __atomic_sub_fetch (x, y, z) (and vice
versa).

2022-01-03  Jakub Jelinek  <jakub@redhat.com>

	PR target/98737
	* internal-fn.def (ATOMIC_ADD_FETCH_CMP_0, ATOMIC_SUB_FETCH_CMP_0,
	ATOMIC_AND_FETCH_CMP_0, ATOMIC_OR_FETCH_CMP_0, ATOMIC_XOR_FETCH_CMP_0):
	New internal fns.
	* internal-fn.h (ATOMIC_OP_FETCH_CMP_0_EQ, ATOMIC_OP_FETCH_CMP_0_NE,
	ATOMIC_OP_FETCH_CMP_0_LT, ATOMIC_OP_FETCH_CMP_0_LE,
	ATOMIC_OP_FETCH_CMP_0_GT, ATOMIC_OP_FETCH_CMP_0_GE): New enumerators.
	* internal-fn.c (expand_ATOMIC_ADD_FETCH_CMP_0,
	expand_ATOMIC_SUB_FETCH_CMP_0, expand_ATOMIC_AND_FETCH_CMP_0,
	expand_ATOMIC_OR_FETCH_CMP_0, expand_ATOMIC_XOR_FETCH_CMP_0): New
	functions.
	* optabs.def (atomic_add_fetch_cmp_0_optab,
	atomic_sub_fetch_cmp_0_optab, atomic_and_fetch_cmp_0_optab,
	atomic_or_fetch_cmp_0_optab, atomic_xor_fetch_cmp_0_optab): New
	direct optabs.
	* builtins.h (expand_ifn_atomic_op_fetch_cmp_0): Declare.
	* builtins.c (expand_ifn_atomic_op_fetch_cmp_0): New function.
	* tree-ssa-ccp.c: Include internal-fn.h.
	(optimize_atomic_bit_test_and): Add . before internal fn call
	in function comment.  Change return type from void to bool and
	return true only if successfully replaced.
	(optimize_atomic_op_fetch_cmp_0): New function.
	(pass_fold_builtins::execute): Use optimize_atomic_op_fetch_cmp_0
	for BUILT_IN_ATOMIC_{ADD,SUB,AND,OR,XOR}_FETCH_{1,2,4,8,16} and
	BUILT_IN_SYNC_{ADD,SUB,AND,OR,XOR}_AND_FETCH_{1,2,4,8,16},
	for *XOR* ones only if optimize_atomic_bit_test_and failed.
	* config/i386/sync.md (atomic_<plusminus_mnemonic>_fetch_cmp_0<mode>,
	atomic_<logic>_fetch_cmp_0<mode>): New define_expand patterns.
	(atomic_add_fetch_cmp_0<mode>_1, atomic_sub_fetch_cmp_0<mode>_1,
	atomic_<logic>_fetch_cmp_0<mode>_1): New define_insn patterns.
	* doc/md.texi (atomic_add_fetch_cmp_0<mode>,
	atomic_sub_fetch_cmp_0<mode>, atomic_and_fetch_cmp_0<mode>,
	atomic_or_fetch_cmp_0<mode>, atomic_xor_fetch_cmp_0<mode>): Document
	new named patterns.

	* gcc.target/i386/pr98737-1.c: New test.
	* gcc.target/i386/pr98737-2.c: New test.
	* gcc.target/i386/pr98737-3.c: New test.
	* gcc.target/i386/pr98737-4.c: New test.
	* gcc.target/i386/pr98737-5.c: New test.
	* gcc.target/i386/pr98737-6.c: New test.
	* gcc.target/i386/pr98737-7.c: New test.

1 files changed, 24 insertions, 0 deletions

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index fc7dc28..19e89ae 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -7918,6 +7918,30 @@ If these patterns are not defined, attempts will be made to use
 counterparts.  If none of these are available a compare-and-swap
 loop will be used.
 
+@cindex @code{atomic_add_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_sub_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_and_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_or_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_xor_fetch_cmp_0@var{mode}} instruction pattern
+@item @samp{atomic_add_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_sub_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_and_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_or_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_xor_fetch_cmp_0@var{mode}}
+These patterns emit code for an atomic operation on memory with memory
+model semantics if the fetch result is used only in a comparison against
+zero.
+Operand 0 is an output operand which contains a boolean result of comparison
+of the value after the operation against zero.  Operand 1 is the memory on
+which the atomic operation is performed.  Operand 2 is the second operand
+to the binary operator.  Operand 3 is the memory model to be used by the
+operation.  Operand 4 is an integer holding the comparison code, one of
+@code{EQ}, @code{NE}, @code{LT}, @code{GT}, @code{LE} or @code{GE}.
+
+If these patterns are not defined, attempts will be made to use separate
+atomic operation and fetch pattern followed by comparison of the result
+against zero.
+
 @cindex @code{mem_thread_fence} instruction pattern
 @item @samp{mem_thread_fence}
 This pattern emits code required to implement a thread fence with