Hi all,
This patch implements the atomic built-ins using the new ARMv8 load-acquire
and store-release instructions.
They allow us to generate barrier-free code for a variety of atomic
operations such as: atomic load, atomic store, atomic compare and swap,
atomic {or, and, add, sub, xor}.
Tests will come in a separate patch soon.
No regressions on arm-none-eabi. Bootstrap on armv7l-unknown-linux-gnueabihf
successful.
Ok for trunk (now or when stage 1 reopens)?
Thanks,
Kyrill
gcc/ChangeLog
2013-01-23 Kyrylo Tkachov <kyrylo.tkachov at arm.com>
* config/arm/arm.c (arm_emit_load_exclusive): Add acq parameter.
Emit load-acquire versions when acq is true.
(arm_emit_store_exclusive): Add rel parameter.
Emit store-release versions when rel is true.
(arm_split_compare_and_swap): Use acquire-release instructions
instead
of barriers when appropriate.
(arm_split_atomic_op): Likewise.
* config/arm/arm.h (TARGET_HAVE_LDACQ): New macro.
* config/arm/unspecs.md (VUNSPEC_LAX): New unspec.
(VUNSPEC_SLX): Likewise.
(VUNSPEC_LDA): Likewise.
(VUNSPEC_STL): Likewise.
* config/arm/sync.md (atomic_load<mode>): New pattern.
(atomic_store<mode>): Likewise.
(arm_load_acquire_exclusive<mode>): Likewise.
(arm_load_acquire_exclusivesi): Likewise.
(arm_load_acquire_exclusivedi): Likewise.
(arm_store_release_exclusive<mode>): Likewise.diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 9d3981d..f989f54 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -25999,39 +25999,71 @@ arm_post_atomic_barrier (enum memmodel model)
emit_insn (gen_memory_barrier ());
}
-/* Emit the load-exclusive and store-exclusive instructions. */
+/* Emit the load-exclusive and store-exclusive instructions.
+ Use acquire and release versions if necessary. */
static void
-arm_emit_load_exclusive (enum machine_mode mode, rtx rval, rtx mem)
+arm_emit_load_exclusive (enum machine_mode mode, rtx rval, rtx mem, bool acq)
{
rtx (*gen) (rtx, rtx);
- switch (mode)
+ if (acq)
{
- case QImode: gen = gen_arm_load_exclusiveqi; break;
- case HImode: gen = gen_arm_load_exclusivehi; break;
- case SImode: gen = gen_arm_load_exclusivesi; break;
- case DImode: gen = gen_arm_load_exclusivedi; break;
- default:
- gcc_unreachable ();
+ switch (mode)
+ {
+ case QImode: gen = gen_arm_load_acquire_exclusiveqi; break;
+ case HImode: gen = gen_arm_load_acquire_exclusivehi; break;
+ case SImode: gen = gen_arm_load_acquire_exclusivesi; break;
+ case DImode: gen = gen_arm_load_acquire_exclusivedi; break;
+ default:
+ gcc_unreachable ();
+ }
+ }
+ else
+ {
+ switch (mode)
+ {
+ case QImode: gen = gen_arm_load_exclusiveqi; break;
+ case HImode: gen = gen_arm_load_exclusivehi; break;
+ case SImode: gen = gen_arm_load_exclusivesi; break;
+ case DImode: gen = gen_arm_load_exclusivedi; break;
+ default:
+ gcc_unreachable ();
+ }
}
emit_insn (gen (rval, mem));
}
static void
-arm_emit_store_exclusive (enum machine_mode mode, rtx bval, rtx rval, rtx mem)
+arm_emit_store_exclusive (enum machine_mode mode, rtx bval, rtx rval,
+ rtx mem, bool rel)
{
rtx (*gen) (rtx, rtx, rtx);
- switch (mode)
+ if (rel)
{
- case QImode: gen = gen_arm_store_exclusiveqi; break;
- case HImode: gen = gen_arm_store_exclusivehi; break;
- case SImode: gen = gen_arm_store_exclusivesi; break;
- case DImode: gen = gen_arm_store_exclusivedi; break;
- default:
- gcc_unreachable ();
+ switch (mode)
+ {
+ case QImode: gen = gen_arm_store_release_exclusiveqi; break;
+ case HImode: gen = gen_arm_store_release_exclusivehi; break;
+ case SImode: gen = gen_arm_store_release_exclusivesi; break;
+ case DImode: gen = gen_arm_store_release_exclusivedi; break;
+ default:
+ gcc_unreachable ();
+ }
+ }
+ else
+ {
+ switch (mode)
+ {
+ case QImode: gen = gen_arm_store_exclusiveqi; break;
+ case HImode: gen = gen_arm_store_exclusivehi; break;
+ case SImode: gen = gen_arm_store_exclusivesi; break;
+ case DImode: gen = gen_arm_store_exclusivedi; break;
+ default:
+ gcc_unreachable ();
+ }
}
emit_insn (gen (bval, rval, mem));
@@ -26067,6 +26099,15 @@ arm_expand_compare_and_swap (rtx operands[])
mod_f = operands[7];
mode = GET_MODE (mem);
+ /* Normally the succ memory model must be stronger than fail, but in the
+ unlikely event of fail being ACQUIRE and succ being RELEASE we need to
+ promote succ to ACQ_REL so that we don't lose the acquire semantics. */
+
+ if (TARGET_HAVE_LDACQ
+ && INTVAL (mod_f) == MEMMODEL_ACQUIRE
+ && INTVAL (mod_s) == MEMMODEL_RELEASE)
+ mod_s = GEN_INT (MEMMODEL_ACQ_REL);
+
switch (mode)
{
case QImode:
@@ -26141,7 +26182,19 @@ arm_split_compare_and_swap (rtx operands[])
scratch = operands[7];
mode = GET_MODE (mem);
- arm_pre_atomic_barrier (mod_s);
+ bool use_acquire = TARGET_HAVE_LDACQ
+ && !(mod_s == MEMMODEL_RELAXED
+ || mod_s == MEMMODEL_CONSUME
+ || mod_s == MEMMODEL_RELEASE);
+
+ bool use_release = TARGET_HAVE_LDACQ
+ && !(mod_s == MEMMODEL_RELAXED
+ || mod_s == MEMMODEL_CONSUME
+ || mod_s == MEMMODEL_ACQUIRE);
+
+ /* Checks whether a barrier is needed and emits one accordingly. */
+ if (!(use_acquire || use_release))
+ arm_pre_atomic_barrier (mod_s);
label1 = NULL_RTX;
if (!is_weak)
@@ -26151,7 +26204,7 @@ arm_split_compare_and_swap (rtx operands[])
}
label2 = gen_label_rtx ();
- arm_emit_load_exclusive (mode, rval, mem);
+ arm_emit_load_exclusive (mode, rval, mem, use_acquire);
cond = arm_gen_compare_reg (NE, rval, oldval, scratch);
x = gen_rtx_NE (VOIDmode, cond, const0_rtx);
@@ -26159,7 +26212,7 @@ arm_split_compare_and_swap (rtx operands[])
gen_rtx_LABEL_REF (Pmode, label2), pc_rtx);
emit_unlikely_jump (gen_rtx_SET (VOIDmode, pc_rtx, x));
- arm_emit_store_exclusive (mode, scratch, mem, newval);
+ arm_emit_store_exclusive (mode, scratch, mem, newval, use_release);
/* Weak or strong, we want EQ to be true for success, so that we
match the flags that we got from the compare above. */
@@ -26178,7 +26231,9 @@ arm_split_compare_and_swap (rtx operands[])
if (mod_f != MEMMODEL_RELAXED)
emit_label (label2);
- arm_post_atomic_barrier (mod_s);
+ /* Checks whether a barrier is needed and emits one accordingly. */
+ if (!(use_acquire || use_release))
+ arm_post_atomic_barrier (mod_s);
if (mod_f == MEMMODEL_RELAXED)
emit_label (label2);
@@ -26193,7 +26248,19 @@ arm_split_atomic_op (enum rtx_code code, rtx old_out,
rtx new_out, rtx mem,
enum machine_mode wmode = (mode == DImode ? DImode : SImode);
rtx label, x;
- arm_pre_atomic_barrier (model);
+ bool use_acquire = TARGET_HAVE_LDACQ
+ && !(model == MEMMODEL_RELAXED
+ || model == MEMMODEL_CONSUME
+ || model == MEMMODEL_RELEASE);
+
+ bool use_release = TARGET_HAVE_LDACQ
+ && !(model == MEMMODEL_RELAXED
+ || model == MEMMODEL_CONSUME
+ || model == MEMMODEL_ACQUIRE);
+
+ /* Checks whether a barrier is needed and emits one accordingly. */
+ if (!(use_acquire || use_release))
+ arm_pre_atomic_barrier (model);
label = gen_label_rtx ();
emit_label (label);
@@ -26206,7 +26273,7 @@ arm_split_atomic_op (enum rtx_code code, rtx old_out,
rtx new_out, rtx mem,
old_out = new_out;
value = simplify_gen_subreg (wmode, value, mode, 0);
- arm_emit_load_exclusive (mode, old_out, mem);
+ arm_emit_load_exclusive (mode, old_out, mem, use_acquire);
switch (code)
{
@@ -26254,12 +26321,15 @@ arm_split_atomic_op (enum rtx_code code, rtx old_out,
rtx new_out, rtx mem,
break;
}
- arm_emit_store_exclusive (mode, cond, mem, gen_lowpart (mode, new_out));
+ arm_emit_store_exclusive (mode, cond, mem, gen_lowpart (mode, new_out),
+ use_release);
x = gen_rtx_NE (VOIDmode, cond, const0_rtx);
emit_unlikely_jump (gen_cbranchsi4 (x, cond, const0_rtx, label));
- arm_post_atomic_barrier (model);
+ /* Checks whether a barrier is needed and emits one accordingly. */
+ if (!(use_acquire || use_release))
+ arm_post_atomic_barrier (model);
}
#define MAX_VECT_LEN 16
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 6d336e8..9ef29a8 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -350,6 +350,9 @@ extern void (*arm_lang_output_object_attributes_hook)(void);
#define TARGET_HAVE_LDREXD (((arm_arch6k && TARGET_ARM) || arm_arch7) \
&& arm_arch_notm)
+/* Nonzero if this chip supports load-acquire and store-release. */
+#define TARGET_HAVE_LDACQ (TARGET_ARM_ARCH >= 8)
+
/* Nonzero if integer division instructions supported. */
#define TARGET_IDIV ((TARGET_ARM && arm_arch_arm_hwdiv) \
|| (TARGET_THUMB2 && arm_arch_thumb_hwdiv))
diff --git a/gcc/config/arm/sync.md b/gcc/config/arm/sync.md
index 281e51e..9802348 100644
--- a/gcc/config/arm/sync.md
+++ b/gcc/config/arm/sync.md
@@ -65,6 +65,42 @@
(set_attr "conds" "unconditional")
(set_attr "predicable" "no")])
+(define_insn "atomic_load<mode>"
+ [(set (match_operand:QHSI 0 "register_operand" "=r")
+ (unspec_volatile:QHSI
+ [(match_operand:QHSI 1 "arm_sync_memory_operand" "Q")
+ (match_operand:SI 2 "const_int_operand")] ;; model
+ VUNSPEC_LDA))]
+ "TARGET_HAVE_LDACQ"
+ {
+ enum memmodel model = (enum memmodel) INTVAL (operands[2]);
+ if (model == MEMMODEL_RELAXED
+ || model == MEMMODEL_CONSUME
+ || model == MEMMODEL_RELEASE)
+ return \"ldr<sync_sfx>\\t%0, %1\";
+ else
+ return \"lda<sync_sfx>\\t%0, %1\";
+ }
+)
+
+(define_insn "atomic_store<mode>"
+ [(set (match_operand:QHSI 0 "memory_operand" "=Q")
+ (unspec_volatile:QHSI
+ [(match_operand:QHSI 1 "general_operand" "r")
+ (match_operand:SI 2 "const_int_operand")] ;; model
+ VUNSPEC_STL))]
+ "TARGET_HAVE_LDACQ"
+ {
+ enum memmodel model = (enum memmodel) INTVAL (operands[2]);
+ if (model == MEMMODEL_RELAXED
+ || model == MEMMODEL_CONSUME
+ || model == MEMMODEL_ACQUIRE)
+ return \"str<sync_sfx>\t%1, %0\";
+ else
+ return \"stl<sync_sfx>\t%1, %0\";
+ }
+)
+
;; Note that ldrd and vldr are *not* guaranteed to be single-copy atomic,
;; even for a 64-bit aligned address. Instead we use a ldrexd unparied
;; with a store.
@@ -327,6 +363,16 @@
"ldrex<sync_sfx>%?\t%0, %C1"
[(set_attr "predicable" "yes")])
+(define_insn "arm_load_acquire_exclusive<mode>"
+ [(set (match_operand:SI 0 "s_register_operand" "=r")
+ (zero_extend:SI
+ (unspec_volatile:NARROW
+ [(match_operand:NARROW 1 "mem_noofs_operand" "Ua")]
+ VUNSPEC_LAX)))]
+ "TARGET_HAVE_LDACQ"
+ "ldaex<sync_sfx>%?\\t%0, %C1"
+ [(set_attr "predicable" "yes")])
+
(define_insn "arm_load_exclusivesi"
[(set (match_operand:SI 0 "s_register_operand" "=r")
(unspec_volatile:SI
@@ -336,6 +382,15 @@
"ldrex%?\t%0, %C1"
[(set_attr "predicable" "yes")])
+(define_insn "arm_load_acquire_exclusivesi"
+ [(set (match_operand:SI 0 "s_register_operand" "=r")
+ (unspec_volatile:SI
+ [(match_operand:SI 1 "mem_noofs_operand" "Ua")]
+ VUNSPEC_LAX))]
+ "TARGET_HAVE_LDACQ"
+ "ldaex%?\t%0, %C1"
+ [(set_attr "predicable" "yes")])
+
(define_insn "arm_load_exclusivedi"
[(set (match_operand:DI 0 "s_register_operand" "=r")
(unspec_volatile:DI
@@ -345,6 +400,15 @@
"ldrexd%?\t%0, %H0, %C1"
[(set_attr "predicable" "yes")])
+(define_insn "arm_load_acquire_exclusivedi"
+ [(set (match_operand:DI 0 "s_register_operand" "=r")
+ (unspec_volatile:DI
+ [(match_operand:DI 1 "mem_noofs_operand" "Ua")]
+ VUNSPEC_LAX))]
+ "TARGET_HAVE_LDACQ && ARM_DOUBLEWORD_ALIGN"
+ "ldaexd%?\t%0, %H0, %C1"
+ [(set_attr "predicable" "yes")])
+
(define_insn "arm_store_exclusive<mode>"
[(set (match_operand:SI 0 "s_register_operand" "=&r")
(unspec_volatile:SI [(const_int 0)] VUNSPEC_SC))
@@ -368,3 +432,31 @@
return "strex<sync_sfx>%?\t%0, %2, %C1";
}
[(set_attr "predicable" "yes")])
+
+(define_insn "arm_store_release_exclusivedi"
+ [(set (match_operand:SI 0 "s_register_operand" "=&r")
+ (unspec_volatile:SI [(const_int 0)] VUNSPEC_SLX))
+ (set (match_operand:DI 1 "mem_noofs_operand" "=Ua")
+ (unspec_volatile:DI
+ [(match_operand:DI 2 "s_register_operand" "r")]
+ VUNSPEC_SLX))]
+ "TARGET_HAVE_LDACQ && ARM_DOUBLEWORD_ALIGN"
+ {
+ rtx value = operands[2];
+ /* See comment in arm_store_exclusive<mode> above. */
+ gcc_assert ((REGNO (value) & 1) == 0 || TARGET_THUMB2);
+ operands[3] = gen_rtx_REG (SImode, REGNO (value) + 1);
+ return "stlexd%?\t%0, %2, %3, %C1";
+ }
+ [(set_attr "predicable" "yes")])
+
+(define_insn "arm_store_release_exclusive<mode>"
+ [(set (match_operand:SI 0 "s_register_operand" "=&r")
+ (unspec_volatile:SI [(const_int 0)] VUNSPEC_SLX))
+ (set (match_operand:QHSI 1 "mem_noofs_operand" "=Ua")
+ (unspec_volatile:QHSI
+ [(match_operand:QHSI 2 "s_register_operand" "r")]
+ VUNSPEC_SLX))]
+ "TARGET_HAVE_LDACQ"
+ "stlex<sync_sfx>%?\t%0, %2, %C1"
+ [(set_attr "predicable" "yes")])
diff --git a/gcc/config/arm/unspecs.md b/gcc/config/arm/unspecs.md
index 3985912..508603c 100644
--- a/gcc/config/arm/unspecs.md
+++ b/gcc/config/arm/unspecs.md
@@ -139,6 +139,10 @@
VUNSPEC_ATOMIC_OP ; Represent an atomic operation.
VUNSPEC_LL ; Represent a load-register-exclusive.
VUNSPEC_SC ; Represent a store-register-exclusive.
+ VUNSPEC_LAX ; Represent a load-register-acquire-exclusive.
+ VUNSPEC_SLX ; Represent a store-register-release-exclusive.
+ VUNSPEC_LDA ; Represent a store-register-acquire.
+ VUNSPEC_STL ; Represent a store-register-release.
])
;; Enumerators for NEON unspecs.
