target-alpha: Emulate LL/SC using cmpxchg helpers
Emulating LL/SC with cmpxchg is not correct, since it can
suffer from the ABA problem. However, portable parallel
code is written assuming only cmpxchg which means that in
practice this is a viable alternative.
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/linux-user/main.c b/linux-user/main.c
index 5ff06ac..75b199f 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2926,51 +2926,6 @@
#endif /* TARGET_M68K */
#ifdef TARGET_ALPHA
-static void do_store_exclusive(CPUAlphaState *env, int reg, int quad)
-{
- target_ulong addr, val, tmp;
- target_siginfo_t info;
- int ret = 0;
-
- addr = env->lock_addr;
- tmp = env->lock_st_addr;
- env->lock_addr = -1;
- env->lock_st_addr = 0;
-
- start_exclusive();
- mmap_lock();
-
- if (addr == tmp) {
- if (quad ? get_user_s64(val, addr) : get_user_s32(val, addr)) {
- goto do_sigsegv;
- }
-
- if (val == env->lock_value) {
- tmp = env->ir[reg];
- if (quad ? put_user_u64(tmp, addr) : put_user_u32(tmp, addr)) {
- goto do_sigsegv;
- }
- ret = 1;
- }
- }
- env->ir[reg] = ret;
- env->pc += 4;
-
- mmap_unlock();
- end_exclusive();
- return;
-
- do_sigsegv:
- mmap_unlock();
- end_exclusive();
-
- info.si_signo = TARGET_SIGSEGV;
- info.si_errno = 0;
- info.si_code = TARGET_SEGV_MAPERR;
- info._sifields._sigfault._addr = addr;
- queue_signal(env, TARGET_SIGSEGV, QEMU_SI_FAULT, &info);
-}
-
void cpu_loop(CPUAlphaState *env)
{
CPUState *cs = CPU(alpha_env_get_cpu(env));
@@ -3145,10 +3100,6 @@
queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
}
break;
- case EXCP_STL_C:
- case EXCP_STQ_C:
- do_store_exclusive(env, env->error_code, trapnr - EXCP_STL_C);
- break;
case EXCP_INTERRUPT:
/* Just indicate that signals should be handled asap. */
break;
diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
index 871d9ba..b08d160 100644
--- a/target-alpha/cpu.h
+++ b/target-alpha/cpu.h
@@ -230,7 +230,6 @@
uint64_t pc;
uint64_t unique;
uint64_t lock_addr;
- uint64_t lock_st_addr;
uint64_t lock_value;
/* The FPCR, and disassembled portions thereof. */
@@ -346,9 +345,6 @@
EXCP_ARITH,
EXCP_FEN,
EXCP_CALL_PAL,
- /* For Usermode emulation. */
- EXCP_STL_C,
- EXCP_STQ_C,
};
/* Alpha-specific interrupt pending bits. */
diff --git a/target-alpha/helper.c b/target-alpha/helper.c
index 9ba3e1a..2ef6cbe 100644
--- a/target-alpha/helper.c
+++ b/target-alpha/helper.c
@@ -306,12 +306,6 @@
case EXCP_CALL_PAL:
name = "call_pal";
break;
- case EXCP_STL_C:
- name = "stl_c";
- break;
- case EXCP_STQ_C:
- name = "stq_c";
- break;
}
qemu_log("INT %6d: %s(%#x) pc=%016" PRIx64 " sp=%016" PRIx64 "\n",
++count, name, env->error_code, env->pc, env->ir[IR_SP]);
diff --git a/target-alpha/machine.c b/target-alpha/machine.c
index 710b783..b99a123 100644
--- a/target-alpha/machine.c
+++ b/target-alpha/machine.c
@@ -45,8 +45,6 @@
VMSTATE_UINTTL(unique, CPUAlphaState),
VMSTATE_UINTTL(lock_addr, CPUAlphaState),
VMSTATE_UINTTL(lock_value, CPUAlphaState),
- /* Note that lock_st_addr is not saved; it is a temporary
- used during the execution of the st[lq]_c insns. */
VMSTATE_UINT8(ps, CPUAlphaState),
VMSTATE_UINT8(intr_flag, CPUAlphaState),
diff --git a/target-alpha/translate.c b/target-alpha/translate.c
index a2e2a62..03e4776 100644
--- a/target-alpha/translate.c
+++ b/target-alpha/translate.c
@@ -99,7 +99,6 @@
static TCGv cpu_fir[31];
static TCGv cpu_pc;
static TCGv cpu_lock_addr;
-static TCGv cpu_lock_st_addr;
static TCGv cpu_lock_value;
#ifndef CONFIG_USER_ONLY
@@ -116,7 +115,6 @@
static const GlobalVar vars[] = {
DEF_VAR(pc),
DEF_VAR(lock_addr),
- DEF_VAR(lock_st_addr),
DEF_VAR(lock_value),
};
@@ -198,6 +196,23 @@
return ctx->sink;
}
+static void free_context_temps(DisasContext *ctx)
+{
+ if (!TCGV_IS_UNUSED_I64(ctx->sink)) {
+ tcg_gen_discard_i64(ctx->sink);
+ tcg_temp_free(ctx->sink);
+ TCGV_UNUSED_I64(ctx->sink);
+ }
+ if (!TCGV_IS_UNUSED_I64(ctx->zero)) {
+ tcg_temp_free(ctx->zero);
+ TCGV_UNUSED_I64(ctx->zero);
+ }
+ if (!TCGV_IS_UNUSED_I64(ctx->lit)) {
+ tcg_temp_free(ctx->lit);
+ TCGV_UNUSED_I64(ctx->lit);
+ }
+}
+
static TCGv load_gpr(DisasContext *ctx, unsigned reg)
{
if (likely(reg < 31)) {
@@ -395,56 +410,37 @@
int32_t disp16, int mem_idx,
TCGMemOp op)
{
- TCGv addr;
+ TCGLabel *lab_fail, *lab_done;
+ TCGv addr, val;
- if (ra == 31) {
- /* ??? Don't bother storing anything. The user can't tell
- the difference, since the zero register always reads zero. */
- return NO_EXIT;
- }
-
-#if defined(CONFIG_USER_ONLY)
- addr = cpu_lock_st_addr;
-#else
- addr = tcg_temp_local_new();
-#endif
-
+ addr = tcg_temp_new_i64();
tcg_gen_addi_i64(addr, load_gpr(ctx, rb), disp16);
+ free_context_temps(ctx);
-#if defined(CONFIG_USER_ONLY)
- /* ??? This is handled via a complicated version of compare-and-swap
- in the cpu_loop. Hopefully one day we'll have a real CAS opcode
- in TCG so that this isn't necessary. */
- return gen_excp(ctx, (op & MO_SIZE) == MO_64 ? EXCP_STQ_C : EXCP_STL_C, ra);
-#else
- /* ??? In system mode we are never multi-threaded, so CAS can be
- implemented via a non-atomic load-compare-store sequence. */
- {
- TCGLabel *lab_fail, *lab_done;
- TCGv val;
+ lab_fail = gen_new_label();
+ lab_done = gen_new_label();
+ tcg_gen_brcond_i64(TCG_COND_NE, addr, cpu_lock_addr, lab_fail);
+ tcg_temp_free_i64(addr);
- lab_fail = gen_new_label();
- lab_done = gen_new_label();
- tcg_gen_brcond_i64(TCG_COND_NE, addr, cpu_lock_addr, lab_fail);
+ val = tcg_temp_new_i64();
+ tcg_gen_atomic_cmpxchg_i64(val, cpu_lock_addr, cpu_lock_value,
+ load_gpr(ctx, ra), mem_idx, op);
+ free_context_temps(ctx);
- val = tcg_temp_new();
- tcg_gen_qemu_ld_i64(val, addr, mem_idx, op);
- tcg_gen_brcond_i64(TCG_COND_NE, val, cpu_lock_value, lab_fail);
-
- tcg_gen_qemu_st_i64(ctx->ir[ra], addr, mem_idx, op);
- tcg_gen_movi_i64(ctx->ir[ra], 1);
- tcg_gen_br(lab_done);
-
- gen_set_label(lab_fail);
- tcg_gen_movi_i64(ctx->ir[ra], 0);
-
- gen_set_label(lab_done);
- tcg_gen_movi_i64(cpu_lock_addr, -1);
-
- tcg_temp_free(addr);
- return NO_EXIT;
+ if (ra != 31) {
+ tcg_gen_setcond_i64(TCG_COND_EQ, ctx->ir[ra], val, cpu_lock_value);
}
-#endif
+ tcg_temp_free_i64(val);
+ tcg_gen_br(lab_done);
+
+ gen_set_label(lab_fail);
+ if (ra != 31) {
+ tcg_gen_movi_i64(ctx->ir[ra], 0);
+ }
+
+ gen_set_label(lab_done);
+ tcg_gen_movi_i64(cpu_lock_addr, -1);
+ return NO_EXIT;
}
static bool in_superpage(DisasContext *ctx, int64_t addr)
@@ -2914,6 +2910,10 @@
/* Similarly for flush-to-zero. */
ctx.tb_ftz = -1;
+ TCGV_UNUSED_I64(ctx.zero);
+ TCGV_UNUSED_I64(ctx.sink);
+ TCGV_UNUSED_I64(ctx.lit);
+
num_insns = 0;
max_insns = tb->cflags & CF_COUNT_MASK;
if (max_insns == 0) {
@@ -2948,23 +2948,9 @@
}
insn = cpu_ldl_code(env, ctx.pc);
- TCGV_UNUSED_I64(ctx.zero);
- TCGV_UNUSED_I64(ctx.sink);
- TCGV_UNUSED_I64(ctx.lit);
-
ctx.pc += 4;
ret = translate_one(ctxp, insn);
-
- if (!TCGV_IS_UNUSED_I64(ctx.sink)) {
- tcg_gen_discard_i64(ctx.sink);
- tcg_temp_free(ctx.sink);
- }
- if (!TCGV_IS_UNUSED_I64(ctx.zero)) {
- tcg_temp_free(ctx.zero);
- }
- if (!TCGV_IS_UNUSED_I64(ctx.lit)) {
- tcg_temp_free(ctx.lit);
- }
+ free_context_temps(ctxp);
/* If we reach a page boundary, are single stepping,
or exhaust instruction count, stop generation. */
