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tcg: Reduce max TB opcode count

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Also, assert that we don't overflow any of two different offsets into
the TB. Both unwind and goto_tb both record a uint16_t for later use.

This fixes an arm-softmmu test case utilizing NEON in which there is
a TB generated that runs to 7800 opcodes, and compiles to 96k on an
x86_64 host.  This overflows the 16-bit offset in which we record the
goto_tb reset offset.  Because of that overflow, we install a jump
destination that goes to neverland.  Boom.

With this reduced op count, the same TB compiles to about 48k for
aarch64, ppc64le, and x86_64 hosts, and neither assertion fires.

Cc: qemu-stable@nongnu.org
Reported-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2018-06-14 19:57:03 -10:00
parent 0ac20318ce
commit 9f75462065
10 changed files with 26 additions and 13 deletions
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2
tcg/s390/tcg-target.inc.c
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@ -1783,7 +1783,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
/* and go there */
tcg_out_insn(s, RR, BCR, S390_CC_ALWAYS, TCG_REG_TB);
}
s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s);
set_jmp_reset_offset(s, a0);
/* For the unlinked path of goto_tb, we need to reset
TCG_REG_TB to the beginning of this TB. */