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tcg/ppc: Enable direct branching tcg_out_goto_tb with TCG_REG_TB

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Direct branch patching was disabled when using TCG_REG_TB in commit
736a1588c1 ("tcg/ppc: Fix race in goto_tb implementation").

The issue with direct branch patching with TCG_REG_TB is the lack of
synchronization between the new TCG_REG_TB being established and the
direct branch being patched in.

If each translation block is responsible for establishing its own
TCG_REG_TB then there can be no synchronization issue.

Make each translation block begin by setting up its own TCG_REG_TB.
Use the preferred 'bcl 20,31,$+4' sequence.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
[rth: Split out tcg_out_tb_start, power9 addpcis]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Jordan Niethe 2023-08-15 16:47:11 +00:00 committed by Richard Henderson
parent 096d118592
commit 03434d5202
1 changed files with 17 additions and 31 deletions
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48
tcg/ppc/tcg-target.c.inc
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@ -2509,9 +2509,6 @@ static void tcg_target_qemu_prologue(TCGContext *s)
tcg_out_mov(s, TCG_TYPE_PTR, TCG_AREG0, tcg_target_call_iarg_regs[0]);
tcg_out32(s, MTSPR | RS(tcg_target_call_iarg_regs[1]) | CTR);
if (USE_REG_TB) {
tcg_out_mov(s, TCG_TYPE_PTR, TCG_REG_TB, tcg_target_call_iarg_regs[1]);
}
tcg_out32(s, BCCTR | BO_ALWAYS);
/* Epilogue */
@ -2529,7 +2526,13 @@ static void tcg_target_qemu_prologue(TCGContext *s)
static void tcg_out_tb_start(TCGContext *s)
{
/* nothing to do */
/* Load TCG_REG_TB. */
if (USE_REG_TB) {
/* bcl 20,31,$+4 (preferred form for getting nia) */
tcg_out32(s, BC | BO_ALWAYS | BI(7, CR_SO) | 0x4 | LK);
tcg_out32(s, MFSPR | RT(TCG_REG_TB) | LR);
tcg_out32(s, ADDI | TAI(TCG_REG_TB, TCG_REG_TB, -4));
}
}
static void tcg_out_exit_tb(TCGContext *s, uintptr_t arg)
@ -2542,32 +2545,22 @@ static void tcg_out_goto_tb(TCGContext *s, int which)
{
uintptr_t ptr = get_jmp_target_addr(s, which);
/* Direct branch will be patched by tb_target_set_jmp_target. */
set_jmp_insn_offset(s, which);
tcg_out32(s, NOP);
/* When branch is out of range, fall through to indirect. */
if (USE_REG_TB) {
ptrdiff_t offset = tcg_tbrel_diff(s, (void *)ptr);
tcg_out_mem_long(s, LD, LDX, TCG_REG_TB, TCG_REG_TB, offset);
/* TODO: Use direct branches when possible. */
set_jmp_insn_offset(s, which);
tcg_out32(s, MTSPR | RS(TCG_REG_TB) | CTR);
tcg_out32(s, BCCTR | BO_ALWAYS);
/* For the unlinked case, need to reset TCG_REG_TB. */
set_jmp_reset_offset(s, which);
tcg_out_mem_long(s, ADDI, ADD, TCG_REG_TB, TCG_REG_TB,
-tcg_current_code_size(s));
tcg_out_mem_long(s, LD, LDX, TCG_REG_TMP1, TCG_REG_TB, offset);
} else {
/* Direct branch will be patched by tb_target_set_jmp_target. */
set_jmp_insn_offset(s, which);
tcg_out32(s, NOP);
/* When branch is out of range, fall through to indirect. */
tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_TMP1, ptr - (int16_t)ptr);
tcg_out_ld(s, TCG_TYPE_PTR, TCG_REG_TMP1, TCG_REG_TMP1, (int16_t)ptr);
tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR);
tcg_out32(s, BCCTR | BO_ALWAYS);
set_jmp_reset_offset(s, which);
}
tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR);
tcg_out32(s, BCCTR | BO_ALWAYS);
set_jmp_reset_offset(s, which);
}
void tb_target_set_jmp_target(const TranslationBlock *tb, int n,
@ -2577,10 +2570,6 @@ void tb_target_set_jmp_target(const TranslationBlock *tb, int n,
intptr_t diff = addr - jmp_rx;
tcg_insn_unit insn;
if (USE_REG_TB) {
return;
}
if (in_range_b(diff)) {
insn = B | (diff & 0x3fffffc);
} else {
@ -2600,9 +2589,6 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc,
switch (opc) {
case INDEX_op_goto_ptr:
tcg_out32(s, MTSPR | RS(args[0]) | CTR);
if (USE_REG_TB) {
tcg_out_mov(s, TCG_TYPE_PTR, TCG_REG_TB, args[0]);
}
tcg_out32(s, ADDI | TAI(TCG_REG_R3, 0, 0));
tcg_out32(s, BCCTR | BO_ALWAYS);
break;