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Re: [AArch64][PATCH 1/5] Use atomic instructions for swap and fetch-update operations.
- From: Matthew Wahab <matthew dot wahab at foss dot arm dot com>
- To: James Greenhalgh <james dot greenhalgh at arm dot com>
- Cc: gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 21 Sep 2015 12:06:40 +0100
- Subject: Re: [AArch64][PATCH 1/5] Use atomic instructions for swap and fetch-update operations.
- Authentication-results: sourceware.org; auth=none
- References: <55FAEC63 dot 7040403 at foss dot arm dot com> <20150918075817 dot GA32711 at arm dot com>
On 18/09/15 08:58, James Greenhalgh wrote:
On Thu, Sep 17, 2015 at 05:37:55PM +0100, Matthew Wahab wrote:
diff --git a/gcc/config/aarch64/atomics.md b/gcc/config/aarch64/atomics.md
index 65d2cc9..0e71002 100644
--- a/gcc/config/aarch64/atomics.md
+++ b/gcc/config/aarch64/atomics.md
@@ -27,6 +27,7 @@
UNSPECV_ATOMIC_CMPSW ; Represent an atomic compare swap.
UNSPECV_ATOMIC_EXCHG ; Represent an atomic exchange.
UNSPECV_ATOMIC_CAS ; Represent an atomic CAS.
+ UNSPECV_ATOMIC_SWP ; Represent an atomic SWP.
UNSPECV_ATOMIC_OP ; Represent an atomic operation.
])
@@ -122,19 +123,19 @@
)
(define_insn_and_split "aarch64_compare_and_swap<mode>_lse"
- [(set (reg:CC CC_REGNUM) ;; bool out
+ [(set (reg:CC CC_REGNUM)
(unspec_volatile:CC [(const_int 0)] UNSPECV_ATOMIC_CMPSW))
- (set (match_operand:GPI 0 "register_operand" "=&r") ;; val out
- (match_operand:GPI 1 "aarch64_sync_memory_operand" "+Q")) ;; memory
+ (set (match_operand:GPI 0 "register_operand" "=&r")
+ (match_operand:GPI 1 "aarch64_sync_memory_operand" "+Q"))
(set (match_dup 1)
(unspec_volatile:GPI
- [(match_operand:GPI 2 "aarch64_plus_operand" "rI") ;; expect
- (match_operand:GPI 3 "register_operand" "r") ;; desired
- (match_operand:SI 4 "const_int_operand") ;; is_weak
- (match_operand:SI 5 "const_int_operand") ;; mod_s
- (match_operand:SI 6 "const_int_operand")] ;; mod_f
+ [(match_operand:GPI 2 "aarch64_plus_operand" "rI")
+ (match_operand:GPI 3 "register_operand" "r")
+ (match_operand:SI 4 "const_int_operand")
+ (match_operand:SI 5 "const_int_operand")
+ (match_operand:SI 6 "const_int_operand")]
I'm not sure I understand the change here, those comments still look helpful
enough for understanding the pattern, what have a I missed?
That was part of an attempt to clean up some code. It's unnecessary and I've dropped
the change.
Attached is the updated patch with some other changes:
- Simplified the atomic_exchange<mode> expander in line with reviews for
other patches in the series.
- Removed the CC clobber from aarch64_atomic_exchange<mode>_lse, it was
over-cautious.
- Added a missing entry to the change log (noting a whitespace fix).
Ok for trunk?
Matthew
gcc/
2015-09-21 Matthew Wahab <matthew.wahab@arm.com>
* config/aarch64/aarch64-protos.h (aarch64_gen_atomic_ldop):
Declare.
* config/aarch64/aarch64.c (aarch64_emit_atomic_swap): New.
(aarch64_gen_atomic_ldop): New.
(aarch64_split_atomic_op): Fix whitespace and add a comment.
* config/aarch64/atomics.md (UNSPECV_ATOMIC_SWP): New.
(aarch64_compare_and_swap<mode>_lse): Fix some whitespace.
(atomic_exchange<mode>): Replace with an expander.
(aarch64_atomic_exchange<mode>): New.
(aarch64_atomic_exchange<mode>_lse): New.
(aarch64_atomic_<atomic_optab><mode>): Fix some whitespace.
(aarch64_atomic_swp<mode>): New.
gcc/testsuite/
2015-09-21 Matthew Wahab <matthew.wahab@arm.com>
* gcc.target/aarch64/atomic-inst-ops.inc: (TEST_MODEL): New.
(TEST_ONE): New.
* gcc.target/aarch64/atomic-inst-swap.c: New.
>From 31226dce8d36be98ca95d9165d4147a3bf84d180 Mon Sep 17 00:00:00 2001
From: Matthew Wahab <matthew.wahab@arm.com>
Date: Fri, 7 Aug 2015 17:18:37 +0100
Subject: [PATCH 1/5] Add atomic SWP instruction
Change-Id: I87bf48526cb11e65edd15691f5eab20446e418c9
---
gcc/config/aarch64/aarch64-protos.h | 1 +
gcc/config/aarch64/aarch64.c | 46 +++++++++++++-
gcc/config/aarch64/atomics.md | 71 ++++++++++++++++++++--
.../gcc.target/aarch64/atomic-inst-ops.inc | 13 ++++
gcc/testsuite/gcc.target/aarch64/atomic-inst-swp.c | 44 ++++++++++++++
5 files changed, 170 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/aarch64/atomic-inst-swp.c
diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index ff19851..eba4c76 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -378,6 +378,7 @@ rtx aarch64_load_tp (rtx);
void aarch64_expand_compare_and_swap (rtx op[]);
void aarch64_split_compare_and_swap (rtx op[]);
void aarch64_gen_atomic_cas (rtx, rtx, rtx, rtx, rtx);
+void aarch64_gen_atomic_ldop (enum rtx_code, rtx, rtx, rtx, rtx);
void aarch64_split_atomic_op (enum rtx_code, rtx, rtx, rtx, rtx, rtx, rtx);
bool aarch64_gen_adjusted_ldpstp (rtx *, bool, enum machine_mode, RTX_CODE);
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 4d2126b..dc05c6e 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -11185,11 +11185,54 @@ aarch64_split_compare_and_swap (rtx operands[])
aarch64_emit_post_barrier (model);
}
+/* Emit an atomic swap. */
+
+static void
+aarch64_emit_atomic_swap (machine_mode mode, rtx dst, rtx value,
+ rtx mem, rtx model)
+{
+ rtx (*gen) (rtx, rtx, rtx, rtx);
+
+ switch (mode)
+ {
+ case QImode: gen = gen_aarch64_atomic_swpqi; break;
+ case HImode: gen = gen_aarch64_atomic_swphi; break;
+ case SImode: gen = gen_aarch64_atomic_swpsi; break;
+ case DImode: gen = gen_aarch64_atomic_swpdi; break;
+ default:
+ gcc_unreachable ();
+ }
+
+ emit_insn (gen (dst, mem, value, model));
+}
+
+/* Emit an atomic operation where the architecture supports it. */
+
+void
+aarch64_gen_atomic_ldop (enum rtx_code code, rtx out_data,
+ rtx mem, rtx value, rtx model_rtx)
+{
+ machine_mode mode = GET_MODE (mem);
+
+ out_data = gen_lowpart (mode, out_data);
+
+ switch (code)
+ {
+ case SET:
+ aarch64_emit_atomic_swap (mode, out_data, value, mem, model_rtx);
+ return;
+
+ default:
+ /* The operation can't be done with atomic instructions. */
+ gcc_unreachable ();
+ }
+}
+
/* Split an atomic operation. */
void
aarch64_split_atomic_op (enum rtx_code code, rtx old_out, rtx new_out, rtx mem,
- rtx value, rtx model_rtx, rtx cond)
+ rtx value, rtx model_rtx, rtx cond)
{
machine_mode mode = GET_MODE (mem);
machine_mode wmode = (mode == DImode ? DImode : SImode);
@@ -11198,6 +11241,7 @@ aarch64_split_atomic_op (enum rtx_code code, rtx old_out, rtx new_out, rtx mem,
rtx_code_label *label;
rtx x;
+ /* Split the atomic operation into a sequence. */
label = gen_label_rtx ();
emit_label (label);
diff --git a/gcc/config/aarch64/atomics.md b/gcc/config/aarch64/atomics.md
index 65d2cc9..cb80539 100644
--- a/gcc/config/aarch64/atomics.md
+++ b/gcc/config/aarch64/atomics.md
@@ -27,6 +27,7 @@
UNSPECV_ATOMIC_CMPSW ; Represent an atomic compare swap.
UNSPECV_ATOMIC_EXCHG ; Represent an atomic exchange.
UNSPECV_ATOMIC_CAS ; Represent an atomic CAS.
+ UNSPECV_ATOMIC_SWP ; Represent an atomic SWP.
UNSPECV_ATOMIC_OP ; Represent an atomic operation.
])
@@ -134,7 +135,7 @@
(match_operand:SI 5 "const_int_operand") ;; mod_s
(match_operand:SI 6 "const_int_operand")] ;; mod_f
UNSPECV_ATOMIC_CMPSW))]
- "TARGET_LSE "
+ "TARGET_LSE"
"#"
"&& reload_completed"
[(const_int 0)]
@@ -146,7 +147,28 @@
}
)
-(define_insn_and_split "atomic_exchange<mode>"
+(define_expand "atomic_exchange<mode>"
+ [(match_operand:ALLI 0 "register_operand" "")
+ (match_operand:ALLI 1 "aarch64_sync_memory_operand" "")
+ (match_operand:ALLI 2 "register_operand" "")
+ (match_operand:SI 3 "const_int_operand" "")]
+ ""
+ {
+ rtx (*gen) (rtx, rtx, rtx, rtx);
+
+ /* Use an atomic SWP when available. */
+ if (TARGET_LSE)
+ gen = gen_aarch64_atomic_exchange<mode>_lse;
+ else
+ gen = gen_aarch64_atomic_exchange<mode>;
+
+ emit_insn (gen (operands[0], operands[1], operands[2], operands[3]));
+
+ DONE;
+ }
+)
+
+(define_insn_and_split "aarch64_atomic_exchange<mode>"
[(set (match_operand:ALLI 0 "register_operand" "=&r") ;; output
(match_operand:ALLI 1 "aarch64_sync_memory_operand" "+Q")) ;; memory
(set (match_dup 1)
@@ -162,7 +184,26 @@
[(const_int 0)]
{
aarch64_split_atomic_op (SET, operands[0], NULL, operands[1],
- operands[2], operands[3], operands[4]);
+ operands[2], operands[3], operands[4]);
+ DONE;
+ }
+)
+
+(define_insn_and_split "aarch64_atomic_exchange<mode>_lse"
+ [(set (match_operand:ALLI 0 "register_operand" "=&r")
+ (match_operand:ALLI 1 "aarch64_sync_memory_operand" "+Q"))
+ (set (match_dup 1)
+ (unspec_volatile:ALLI
+ [(match_operand:ALLI 2 "register_operand" "r")
+ (match_operand:SI 3 "const_int_operand" "")]
+ UNSPECV_ATOMIC_EXCHG))]
+ "TARGET_LSE"
+ "#"
+ "&& reload_completed"
+ [(const_int 0)]
+ {
+ aarch64_gen_atomic_ldop (SET, operands[0], operands[1],
+ operands[2], operands[3]);
DONE;
}
)
@@ -183,7 +224,7 @@
[(const_int 0)]
{
aarch64_split_atomic_op (<CODE>, NULL, operands[3], operands[0],
- operands[1], operands[2], operands[4]);
+ operands[1], operands[2], operands[4]);
DONE;
}
)
@@ -425,6 +466,28 @@
;; ARMv8.1 LSE instructions.
+;; Atomic swap with memory.
+(define_insn "aarch64_atomic_swp<mode>"
+ [(set (match_operand:ALLI 0 "register_operand" "+&r")
+ (match_operand:ALLI 1 "aarch64_sync_memory_operand" "+Q"))
+ (set (match_dup 1)
+ (unspec_volatile:ALLI
+ [(match_operand:ALLI 2 "register_operand" "r")
+ (match_operand:SI 3 "const_int_operand" "")]
+ UNSPECV_ATOMIC_SWP))]
+ "TARGET_LSE && reload_completed"
+ {
+ enum memmodel model = memmodel_from_int (INTVAL (operands[3]));
+ if (is_mm_relaxed (model))
+ return "swp<atomic_sfx>\t%<w>2, %<w>0, %1";
+ else if (is_mm_acquire (model) || is_mm_consume (model))
+ return "swpa<atomic_sfx>\t%<w>2, %<w>0, %1";
+ else if (is_mm_release (model))
+ return "swpl<atomic_sfx>\t%<w>2, %<w>0, %1";
+ else
+ return "swpal<atomic_sfx>\t%<w>2, %<w>0, %1";
+ })
+
;; Atomic compare-and-swap: HI and smaller modes.
(define_insn "aarch64_atomic_cas<mode>"
diff --git a/gcc/testsuite/gcc.target/aarch64/atomic-inst-ops.inc b/gcc/testsuite/gcc.target/aarch64/atomic-inst-ops.inc
index 72c7e5c..c2fdcba 100644
--- a/gcc/testsuite/gcc.target/aarch64/atomic-inst-ops.inc
+++ b/gcc/testsuite/gcc.target/aarch64/atomic-inst-ops.inc
@@ -32,6 +32,15 @@ typedef __uint128_t uint128;
TEST_M##N (NAME, FN, int128, MODEL1, MODEL2) \
TEST_M##N (NAME, FN, uint128, MODEL1, MODEL2)
+/* Models to test. */
+#define TEST_MODEL(NAME, FN, N) \
+ TEST_TY (NAME##_relaxed, FN, N, __ATOMIC_RELAXED, DUMMY) \
+ TEST_TY (NAME##_consume, FN, N, __ATOMIC_CONSUME, DUMMY) \
+ TEST_TY (NAME##_acquire, FN, N, __ATOMIC_ACQUIRE, DUMMY) \
+ TEST_TY (NAME##_release, FN, N, __ATOMIC_RELEASE, DUMMY) \
+ TEST_TY (NAME##_acq_rel, FN, N, __ATOMIC_ACQ_REL, DUMMY) \
+ TEST_TY (NAME##_seq_cst, FN, N, __ATOMIC_SEQ_CST, DUMMY) \
+
/* Cross-product of models to test. */
#define TEST_MODEL_M1(NAME, FN, N, M) \
TEST_TY (NAME##_relaxed, FN, N, M, __ATOMIC_RELAXED) \
@@ -51,3 +60,7 @@ typedef __uint128_t uint128;
/* Expand functions for a cross-product of memory models and types. */
#define TEST_TWO(NAME, FN) TEST_MODEL_M2 (NAME, FN)
+
+/* Expand functions for a set of memory models and types. */
+#define TEST_ONE(NAME, FN) TEST_MODEL (NAME, FN, 1)
+
diff --git a/gcc/testsuite/gcc.target/aarch64/atomic-inst-swp.c b/gcc/testsuite/gcc.target/aarch64/atomic-inst-swp.c
new file mode 100644
index 0000000..dabc9b9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/atomic-inst-swp.c
@@ -0,0 +1,44 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8-a+lse" } */
+
+/* Test ARMv8.1-A SWP instruction. */
+
+#include "atomic-inst-ops.inc"
+
+#define TEST TEST_ONE
+
+#define SWAP_ATOMIC(FN, TY, MODEL) \
+ TY FNNAME (FN, TY) (TY* val, TY foo) \
+ { \
+ return __atomic_exchange_n (val, foo, MODEL); \
+ }
+
+#define SWAP_ATOMIC_NORETURN(FN, TY, MODEL) \
+ void FNNAME (FN, TY) (TY* val, TY* foo, TY* bar) \
+ { \
+ __atomic_exchange (val, foo, bar, MODEL); \
+ }
+
+
+TEST (swap_atomic, SWAP_ATOMIC)
+TEST (swap_atomic_noreturn, SWAP_ATOMIC_NORETURN)
+
+
+/* { dg-final { scan-assembler-times "swpb\t" 4} } */
+/* { dg-final { scan-assembler-times "swpab\t" 8} } */
+/* { dg-final { scan-assembler-times "swplb\t" 4} } */
+/* { dg-final { scan-assembler-times "swpalb\t" 8} } */
+
+/* { dg-final { scan-assembler-times "swph\t" 4} } */
+/* { dg-final { scan-assembler-times "swpah\t" 8} } */
+/* { dg-final { scan-assembler-times "swplh\t" 4} } */
+/* { dg-final { scan-assembler-times "swpalh\t" 8} } */
+
+/* { dg-final { scan-assembler-times "swp\t" 8} } */
+/* { dg-final { scan-assembler-times "swpa\t" 16} } */
+/* { dg-final { scan-assembler-times "swpl\t" 8} } */
+/* { dg-final { scan-assembler-times "swpal\t" 16} } */
+
+/* { dg-final { scan-assembler-not "ldaxr\t" } } */
+/* { dg-final { scan-assembler-not "stlxr\t" } } */
+/* { dg-final { scan-assembler-not "dmb" } } */
--
2.1.4