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authorRichard Henderson <rth@twiddle.net>2016-09-02 12:52:28 -0700
committerRichard Henderson <rth@twiddle.net>2016-10-26 08:29:02 -0700
commited2839166c21e001d15868f4d9591a21aaebd547 (patch)
treee63b55476274f12975030d67772d4a4db99c6f5e /target-alpha
parent6a73ecf5cfcd39b7afb5d6a24174730eac49d4b5 (diff)
downloadqemu-arm-ed2839166c21e001d15868f4d9591a21aaebd547.tar.gz
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>
Diffstat (limited to 'target-alpha')
-rw-r--r--target-alpha/cpu.h4
-rw-r--r--target-alpha/helper.c6
-rw-r--r--target-alpha/machine.c2
-rw-r--r--target-alpha/translate.c104
4 files changed, 45 insertions, 71 deletions
diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
index 871d9baa35..b08d1601d1 100644
--- a/target-alpha/cpu.h
+++ b/target-alpha/cpu.h
@@ -230,7 +230,6 @@ struct CPUAlphaState {
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 @@ enum {
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 9ba3e1a1b8..2ef6cbe2a4 100644
--- a/target-alpha/helper.c
+++ b/target-alpha/helper.c
@@ -306,12 +306,6 @@ void alpha_cpu_do_interrupt(CPUState *cs)
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 710b7835b4..b99a123a39 100644
--- a/target-alpha/machine.c
+++ b/target-alpha/machine.c
@@ -45,8 +45,6 @@ static VMStateField vmstate_env_fields[] = {
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 a2e2a62098..03e47765ed 100644
--- a/target-alpha/translate.c
+++ b/target-alpha/translate.c
@@ -99,7 +99,6 @@ static TCGv cpu_std_ir[31];
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 @@ void alpha_translate_init(void)
static const GlobalVar vars[] = {
DEF_VAR(pc),
DEF_VAR(lock_addr),
- DEF_VAR(lock_st_addr),
DEF_VAR(lock_value),
};
@@ -198,6 +196,23 @@ static TCGv dest_sink(DisasContext *ctx)
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 @@ static ExitStatus gen_store_conditional(DisasContext *ctx, int ra, int rb,
int32_t disp16, int mem_idx,
TCGMemOp op)
{
- TCGv addr;
-
- 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
+ TCGLabel *lab_fail, *lab_done;
+ TCGv addr, val;
+ 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);
+ if (ra != 31) {
+ tcg_gen_setcond_i64(TCG_COND_EQ, ctx->ir[ra], val, cpu_lock_value);
+ }
+ tcg_temp_free_i64(val);
+ tcg_gen_br(lab_done);
- gen_set_label(lab_fail);
+ 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);
-
- tcg_temp_free(addr);
- return NO_EXIT;
}
-#endif
+
+ 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 @@ void gen_intermediate_code(CPUAlphaState *env, struct TranslationBlock *tb)
/* 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 @@ void gen_intermediate_code(CPUAlphaState *env, struct TranslationBlock *tb)
}
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. */