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tcg/riscv: Implement direct branch for goto_tb 

Now that tcg can handle direct and indirect goto_tb simultaneously,
we can optimistically leave space for a direct branch and fall back
to loading the pointer from the TB for an indirect branch.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2022-11-27 01:11:56 -08:00
parent 9ae958e4d7
commit 493c9b19a7
1 changed files with 17 additions and 2 deletions
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19
tcg/riscv/tcg-target.c.inc
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@ -1303,7 +1303,11 @@ static void tcg_out_exit_tb(TCGContext *s, uintptr_t a0)
static void tcg_out_goto_tb(TCGContext *s, int which)
{
/* indirect jump method */
/* Direct branch will be patched by tb_target_set_jmp_target. */
set_jmp_insn_offset(s, which);
tcg_out32(s, OPC_JAL);
/* When branch is out of range, fall through to indirect. */
tcg_out_ld(s, TCG_TYPE_PTR, TCG_REG_TMP0, TCG_REG_ZERO,
get_jmp_target_addr(s, which));
tcg_out_opc_imm(s, OPC_JALR, TCG_REG_ZERO, TCG_REG_TMP0, 0);
@ -1313,7 +1317,18 @@ static void tcg_out_goto_tb(TCGContext *s, int which)
void tb_target_set_jmp_target(const TranslationBlock *tb, int n,
uintptr_t jmp_rx, uintptr_t jmp_rw)
{
/* Always indirect, nothing to do */
uintptr_t addr = tb->jmp_target_addr[n];
ptrdiff_t offset = addr - jmp_rx;
tcg_insn_unit insn;
/* Either directly branch, or fall through to indirect branch. */
if (offset == sextreg(offset, 0, 20)) {
insn = encode_uj(OPC_JAL, TCG_REG_ZERO, offset);
} else {
insn = OPC_NOP;
}
qatomic_set((uint32_t *)jmp_rw, insn);
flush_idcache_range(jmp_rx, jmp_rw, 4);
}
static void tcg_out_op(TCGContext *s, TCGOpcode opc,