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tcg/tcg-op: Document bswap32_i64() byte pattern

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Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230823145542.79633-5-philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Philippe Mathieu-Daudé 2023-08-23 16:55:38 +02:00 committed by Richard Henderson
parent 9296455697
commit 9c40621584
1 changed files with 10 additions and 1 deletions
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11
tcg/tcg-op.c
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@ -1822,6 +1822,14 @@ void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg, int flags)
}
}
/*
* bswap32_i64: 32-bit byte swap on the low bits of a 64-bit value.
*
* Byte pattern: xxxxabcd -> yyyydcba
*
* With TCG_BSWAP_IZ, x == zero, else undefined.
* With TCG_BSWAP_OZ, y == zero, with TCG_BSWAP_OS y == sign, else undefined.
*/
void tcg_gen_bswap32_i64(TCGv_i64 ret, TCGv_i64 arg, int flags)
{
/* Only one extension flag may be present. */
@ -1855,7 +1863,8 @@ void tcg_gen_bswap32_i64(TCGv_i64 ret, TCGv_i64 arg, int flags)
} else {
tcg_gen_shri_i64(t1, t1, 32); /* t1 = ....dc.. */
}
tcg_gen_or_i64(ret, t0, t1); /* ret = ssssdcba */
tcg_gen_or_i64(ret, t0, t1); /* ret = ssssdcba (OS) */
/* ....dcba (else) */
tcg_temp_free_i64(t0);
tcg_temp_free_i64(t1);