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[PATCH 1/7] tcg/tcg-op: Document bswap16() byte pattern
From: |
Philippe Mathieu-Daudé |
Subject: |
[PATCH 1/7] tcg/tcg-op: Document bswap16() byte pattern |
Date: |
Tue, 22 Aug 2023 11:37:06 +0200 |
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
tcg/tcg-op.c | 48 ++++++++++++++++++++++++++++++++----------------
1 file changed, 32 insertions(+), 16 deletions(-)
diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index 7aadb37756..f164ddc95e 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -1021,6 +1021,13 @@ void tcg_gen_ext16u_i32(TCGv_i32 ret, TCGv_i32 arg)
}
}
+/*
+ * bswap16_i32: 16-bit byte swap on the low bits of a 32-bit value.
+ *
+ * Byte pattern: bswap16_i32(xxab) -> ..ba (TCG_BSWAP_OZ)
+ * bswap16_i32(xxab) -> ssba (TCG_BSWAP_OS)
+ * bswap16_i32(xxab) -> xxba
+ */
void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg, int flags)
{
/* Only one extension flag may be present. */
@@ -1032,22 +1039,23 @@ void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg,
int flags)
TCGv_i32 t0 = tcg_temp_ebb_new_i32();
TCGv_i32 t1 = tcg_temp_ebb_new_i32();
- tcg_gen_shri_i32(t0, arg, 8);
+ /* arg = xxab */
+ tcg_gen_shri_i32(t0, arg, 8); /* t0 = .xxa */
if (!(flags & TCG_BSWAP_IZ)) {
- tcg_gen_ext8u_i32(t0, t0);
+ tcg_gen_ext8u_i32(t0, t0); /* t0 = ...a */
}
if (flags & TCG_BSWAP_OS) {
- tcg_gen_shli_i32(t1, arg, 24);
- tcg_gen_sari_i32(t1, t1, 16);
+ tcg_gen_shli_i32(t1, arg, 24); /* t1 = b... */
+ tcg_gen_sari_i32(t1, t1, 16); /* t1 = ssb. */
} else if (flags & TCG_BSWAP_OZ) {
- tcg_gen_ext8u_i32(t1, arg);
- tcg_gen_shli_i32(t1, t1, 8);
+ tcg_gen_ext8u_i32(t1, arg); /* t1 = ...b */
+ tcg_gen_shli_i32(t1, t1, 8); /* t1 = ..b. */
} else {
- tcg_gen_shli_i32(t1, arg, 8);
+ tcg_gen_shli_i32(t1, arg, 8); /* t1 = xab. */
}
- tcg_gen_or_i32(ret, t0, t1);
+ tcg_gen_or_i32(ret, t0, t1); /* ret = ssba */
tcg_temp_free_i32(t0);
tcg_temp_free_i32(t1);
}
@@ -1721,6 +1729,13 @@ void tcg_gen_ext32u_i64(TCGv_i64 ret, TCGv_i64 arg)
}
}
+/*
+ * bswap16_i64: 16-bit byte swap on the low bits of a 64-bit value.
+ *
+ * Byte pattern: bswap16_i32(xxxxxxab) -> ......ba (TCG_BSWAP_OZ)
+ * bswap16_i32(xxxxxxab) -> ssssssba (TCG_BSWAP_OS)
+ * bswap16_i32(xxxxxxab) -> xxxxxxba
+ */
void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg, int flags)
{
/* Only one extension flag may be present. */
@@ -1739,22 +1754,23 @@ void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg,
int flags)
TCGv_i64 t0 = tcg_temp_ebb_new_i64();
TCGv_i64 t1 = tcg_temp_ebb_new_i64();
- tcg_gen_shri_i64(t0, arg, 8);
+ /* arg = xxxxxxab */
+ tcg_gen_shri_i64(t0, arg, 8); /* t0 = .xxxxxxa */
if (!(flags & TCG_BSWAP_IZ)) {
- tcg_gen_ext8u_i64(t0, t0);
+ tcg_gen_ext8u_i64(t0, t0); /* t0 = .......a */
}
if (flags & TCG_BSWAP_OS) {
- tcg_gen_shli_i64(t1, arg, 56);
- tcg_gen_sari_i64(t1, t1, 48);
+ tcg_gen_shli_i64(t1, arg, 56); /* t1 = b....... */
+ tcg_gen_sari_i64(t1, t1, 48); /* t1 = ssssssb. */
} else if (flags & TCG_BSWAP_OZ) {
- tcg_gen_ext8u_i64(t1, arg);
- tcg_gen_shli_i64(t1, t1, 8);
+ tcg_gen_ext8u_i64(t1, arg); /* t1 = .......b */
+ tcg_gen_shli_i64(t1, t1, 8); /* t1 = ......b. */
} else {
- tcg_gen_shli_i64(t1, arg, 8);
+ tcg_gen_shli_i64(t1, arg, 8); /* t1 = xxxxxxb. */
}
- tcg_gen_or_i64(ret, t0, t1);
+ tcg_gen_or_i64(ret, t0, t1); /* ret = ssssssba */
tcg_temp_free_i64(t0);
tcg_temp_free_i64(t1);
}
--
2.41.0
[PATCH 2/7] tcg/tcg-op: Document bswap32() byte pattern, Philippe Mathieu-Daudé, 2023/08/22
[PATCH 3/7] tcg/tcg-op: Document bswap64() byte pattern, Philippe Mathieu-Daudé, 2023/08/22