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* [gcc r13-6371] libstdc++: Add likely/unlikely attributes to <codecvt> implementation
@ 2023-02-28 9:49 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2023-02-28 9:49 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:a41a56dee5c2d48337739d60c43cab5074bcc8e7
commit r13-6371-ga41a56dee5c2d48337739d60c43cab5074bcc8e7
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Fri Feb 24 21:28:11 2023 +0000
libstdc++: Add likely/unlikely attributes to <codecvt> implementation
For the common case of converting valid text this improves performance
significantly.
libstdc++-v3/ChangeLog:
* src/c++11/codecvt.cc: Add [[likely]] and [[unlikely]]
attributes.
Diff:
---
libstdc++-v3/src/c++11/codecvt.cc | 92 +++++++++++++++++++--------------------
1 file changed, 46 insertions(+), 46 deletions(-)
diff --git a/libstdc++-v3/src/c++11/codecvt.cc b/libstdc++-v3/src/c++11/codecvt.cc
index e333e795f48..02f05752de8 100644
--- a/libstdc++-v3/src/c++11/codecvt.cc
+++ b/libstdc++-v3/src/c++11/codecvt.cc
@@ -256,19 +256,19 @@ namespace
return incomplete_mb_character;
char32_t c1 = (unsigned char) from[0];
// https://en.wikipedia.org/wiki/UTF-8#Sample_code
- if (c1 < 0x80)
+ if (c1 < 0x80) [[likely]]
{
++from;
return c1;
}
- else if (c1 < 0xC2) // continuation or overlong 2-byte sequence
+ else if (c1 < 0xC2) [[unlikely]] // continuation or overlong 2-byte sequence
return invalid_mb_sequence;
else if (c1 < 0xE0) // 2-byte sequence
{
- if (avail < 2)
+ if (avail < 2) [[unlikely]]
return incomplete_mb_character;
char32_t c2 = (unsigned char) from[1];
- if ((c2 & 0xC0) != 0x80)
+ if ((c2 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
char32_t c = (c1 << 6) + c2 - 0x3080;
if (c <= maxcode)
@@ -277,17 +277,17 @@ namespace
}
else if (c1 < 0xF0) // 3-byte sequence
{
- if (avail < 2)
+ if (avail < 2) [[unlikely]]
return incomplete_mb_character;
char32_t c2 = (unsigned char) from[1];
- if ((c2 & 0xC0) != 0x80)
+ if ((c2 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
- if (c1 == 0xE0 && c2 < 0xA0) // overlong
+ if (c1 == 0xE0 && c2 < 0xA0) [[unlikely]] // overlong
return invalid_mb_sequence;
- if (avail < 3)
+ if (avail < 3) [[unlikely]]
return incomplete_mb_character;
char32_t c3 = (unsigned char) from[2];
- if ((c3 & 0xC0) != 0x80)
+ if ((c3 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
char32_t c = (c1 << 12) + (c2 << 6) + c3 - 0xE2080;
if (c <= maxcode)
@@ -296,31 +296,31 @@ namespace
}
else if (c1 < 0xF5 && maxcode > 0xFFFF) // 4-byte sequence
{
- if (avail < 2)
+ if (avail < 2) [[unlikely]]
return incomplete_mb_character;
char32_t c2 = (unsigned char) from[1];
- if ((c2 & 0xC0) != 0x80)
+ if ((c2 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
- if (c1 == 0xF0 && c2 < 0x90) // overlong
+ if (c1 == 0xF0 && c2 < 0x90) [[unlikely]] // overlong
return invalid_mb_sequence;
- if (c1 == 0xF4 && c2 >= 0x90) // > U+10FFFF
+ if (c1 == 0xF4 && c2 >= 0x90) [[unlikely]] // > U+10FFFF
return invalid_mb_sequence;
- if (avail < 3)
+ if (avail < 3) [[unlikely]]
return incomplete_mb_character;
char32_t c3 = (unsigned char) from[2];
- if ((c3 & 0xC0) != 0x80)
+ if ((c3 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
- if (avail < 4)
+ if (avail < 4) [[unlikely]]
return incomplete_mb_character;
char32_t c4 = (unsigned char) from[3];
- if ((c4 & 0xC0) != 0x80)
+ if ((c4 & 0xC0) != 0x80) [[unlikely]]
return invalid_mb_sequence;
char32_t c = (c1 << 18) + (c2 << 12) + (c3 << 6) + c4 - 0x3C82080;
if (c <= maxcode)
from += 4;
return c;
}
- else // > U+10FFFF
+ else [[unlikely]] // > U+10FFFF
return invalid_mb_sequence;
}
@@ -330,20 +330,20 @@ namespace
{
if (code_point < 0x80)
{
- if (to.size() < 1)
+ if (to.size() < 1) [[unlikely]]
return false;
to = code_point;
}
else if (code_point <= 0x7FF)
{
- if (to.size() < 2)
+ if (to.size() < 2) [[unlikely]]
return false;
to = (code_point >> 6) + 0xC0;
to = (code_point & 0x3F) + 0x80;
}
else if (code_point <= 0xFFFF)
{
- if (to.size() < 3)
+ if (to.size() < 3) [[unlikely]]
return false;
to = (code_point >> 12) + 0xE0;
to = ((code_point >> 6) & 0x3F) + 0x80;
@@ -351,14 +351,14 @@ namespace
}
else if (code_point <= 0x10FFFF)
{
- if (to.size() < 4)
+ if (to.size() < 4) [[unlikely]]
return false;
to = (code_point >> 18) + 0xF0;
to = ((code_point >> 12) & 0x3F) + 0x80;
to = ((code_point >> 6) & 0x3F) + 0x80;
to = (code_point & 0x3F) + 0x80;
}
- else
+ else [[unlikely]]
return false;
return true;
}
@@ -403,16 +403,16 @@ namespace
unsigned long maxcode, codecvt_mode mode)
{
const size_t avail = from.size();
- if (avail == 0)
+ if (avail == 0) [[unlikely]]
return incomplete_mb_character;
int inc = 1;
char32_t c = adjust_byte_order(from[0], mode);
if (is_high_surrogate(c))
{
- if (avail < 2)
+ if (avail < 2) [[unlikely]]
return incomplete_mb_character;
const char16_t c2 = adjust_byte_order(from[1], mode);
- if (is_low_surrogate(c2))
+ if (is_low_surrogate(c2)) [[likely]]
{
c = surrogate_pair_to_code_point(c, c2);
inc = 2;
@@ -420,7 +420,7 @@ namespace
else
return invalid_mb_sequence;
}
- else if (is_low_surrogate(c))
+ else if (is_low_surrogate(c)) [[unlikely]]
return invalid_mb_sequence;
if (c <= maxcode)
from += inc;
@@ -464,9 +464,9 @@ namespace
while (from.size() && to.size())
{
const char32_t codepoint = read_utf8_code_point(from, maxcode);
- if (codepoint == incomplete_mb_character)
+ if (codepoint == incomplete_mb_character) [[unlikely]]
return codecvt_base::partial;
- if (codepoint > maxcode)
+ if (codepoint > maxcode) [[unlikely]]
return codecvt_base::error;
to = codepoint;
}
@@ -479,14 +479,14 @@ namespace
ucs4_out(range<const char32_t>& from, range<C>& to,
unsigned long maxcode = max_code_point, codecvt_mode mode = {})
{
- if (!write_utf8_bom(to, mode))
+ if (!write_utf8_bom(to, mode)) [[unlikely]]
return codecvt_base::partial;
while (from.size())
{
const char32_t c = from[0];
- if (c > maxcode)
+ if (c > maxcode) [[unlikely]]
return codecvt_base::error;
- if (!write_utf8_code_point(to, c))
+ if (!write_utf8_code_point(to, c)) [[unlikely]]
return codecvt_base::partial;
++from;
}
@@ -502,9 +502,9 @@ namespace
while (from.size() && to.size())
{
const char32_t codepoint = read_utf16_code_point(from, maxcode, mode);
- if (codepoint == incomplete_mb_character)
+ if (codepoint == incomplete_mb_character) [[unlikely]]
return codecvt_base::partial;
- if (codepoint > maxcode)
+ if (codepoint > maxcode) [[unlikely]]
return codecvt_base::error;
to = codepoint;
}
@@ -516,14 +516,14 @@ namespace
ucs4_out(range<const char32_t>& from, range<char16_t, false>& to,
unsigned long maxcode = max_code_point, codecvt_mode mode = {})
{
- if (!write_utf16_bom(to, mode))
+ if (!write_utf16_bom(to, mode)) [[unlikely]]
return codecvt_base::partial;
while (from.size())
{
const char32_t c = from[0];
- if (c > maxcode)
+ if (c > maxcode) [[unlikely]]
return codecvt_base::error;
- if (!write_utf16_code_point(to, c, mode))
+ if (!write_utf16_code_point(to, c, mode)) [[unlikely]]
return codecvt_base::partial;
++from;
}
@@ -544,11 +544,11 @@ namespace
{
auto orig = from;
const char32_t codepoint = read_utf8_code_point(from, maxcode);
- if (codepoint == incomplete_mb_character)
+ if (codepoint == incomplete_mb_character) [[unlikely]]
return codecvt_base::partial;
if (codepoint > maxcode)
return codecvt_base::error;
- if (!write_utf16_code_point(to, codepoint, mode))
+ if (!write_utf16_code_point(to, codepoint, mode)) [[unlikely]]
{
from = orig; // rewind to previous position
return codecvt_base::partial;
@@ -564,7 +564,7 @@ namespace
unsigned long maxcode = max_code_point, codecvt_mode mode = {},
surrogates s = surrogates::allowed)
{
- if (!write_utf8_bom(to, mode))
+ if (!write_utf8_bom(to, mode)) [[unlikely]]
return codecvt_base::partial;
while (from.size())
{
@@ -572,14 +572,14 @@ namespace
int inc = 1;
if (is_high_surrogate(c))
{
- if (s == surrogates::disallowed)
+ if (s == surrogates::disallowed) [[unlikely]]
return codecvt_base::error; // No surrogates in UCS-2
- if (from.size() < 2)
+ if (from.size() < 2) [[unlikely]]
return codecvt_base::partial; // stop converting at this point
const char32_t c2 = from[1];
- if (is_low_surrogate(c2))
+ if (is_low_surrogate(c2)) [[likely]]
{
c = surrogate_pair_to_code_point(c, c2);
inc = 2;
@@ -587,11 +587,11 @@ namespace
else
return codecvt_base::error;
}
- else if (is_low_surrogate(c))
+ else if (is_low_surrogate(c)) [[unlikely]]
return codecvt_base::error;
- if (c > maxcode)
+ if (c > maxcode) [[unlikely]]
return codecvt_base::error;
- if (!write_utf8_code_point(to, c))
+ if (!write_utf8_code_point(to, c)) [[unlikely]]
return codecvt_base::partial;
from += inc;
}
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