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* [PATCH v7 1/1] pg_lfind32(): add "overlap" code for remaining elements
@ 2024-03-20 19:20 Nathan Bossart <[email protected]>
0 siblings, 0 replies; 4+ messages in thread
From: Nathan Bossart @ 2024-03-20 19:20 UTC (permalink / raw)
---
src/include/port/pg_lfind.h | 105 ++++++++++++++++++++++++------------
1 file changed, 72 insertions(+), 33 deletions(-)
diff --git a/src/include/port/pg_lfind.h b/src/include/port/pg_lfind.h
index b8dfa66eef..5830cc7cb3 100644
--- a/src/include/port/pg_lfind.h
+++ b/src/include/port/pg_lfind.h
@@ -80,6 +80,51 @@ pg_lfind8_le(uint8 key, uint8 *base, uint32 nelem)
return false;
}
+#ifndef USE_NO_SIMD
+/*
+ * pg_lfind32_helper
+ *
+ * Searches one 4-register-block of integers. The caller is responsible for
+ * ensuring that there are at least 4-registers-worth of integers remaining.
+ */
+static inline bool
+pg_lfind32_helper(const Vector32 keys, uint32 *base)
+{
+ const uint32 nelem_per_vector = sizeof(Vector32) / sizeof(uint32);
+ Vector32 vals1,
+ vals2,
+ vals3,
+ vals4,
+ result1,
+ result2,
+ result3,
+ result4,
+ tmp1,
+ tmp2,
+ result;
+
+ /* load the next block into 4 registers */
+ vector32_load(&vals1, base);
+ vector32_load(&vals2, &base[nelem_per_vector]);
+ vector32_load(&vals3, &base[nelem_per_vector * 2]);
+ vector32_load(&vals4, &base[nelem_per_vector * 3]);
+
+ /* compare each value to the key */
+ result1 = vector32_eq(keys, vals1);
+ result2 = vector32_eq(keys, vals2);
+ result3 = vector32_eq(keys, vals3);
+ result4 = vector32_eq(keys, vals4);
+
+ /* combine the results into a single variable */
+ tmp1 = vector32_or(result1, result2);
+ tmp2 = vector32_or(result3, result4);
+ result = vector32_or(tmp1, tmp2);
+
+ /* return whether there was a match */
+ return vector32_is_highbit_set(result);
+}
+#endif /* ! USE_NO_SIMD */
+
/*
* pg_lfind32
*
@@ -119,46 +164,40 @@ pg_lfind32(uint32 key, uint32 *base, uint32 nelem)
}
#endif
- for (i = 0; i < tail_idx; i += nelem_per_iteration)
+ /*
+ * If there aren't enough elements for the SIMD code, jump to the standard
+ * one-by-one linear search code.
+ */
+ if (nelem <= nelem_per_iteration)
+ goto one_by_one;
+
+ /*
+ * Process as many elements as possible with a block of 4 registers.
+ */
+ do
{
- Vector32 vals1,
- vals2,
- vals3,
- vals4,
- result1,
- result2,
- result3,
- result4,
- tmp1,
- tmp2,
- result;
-
- /* load the next block into 4 registers */
- vector32_load(&vals1, &base[i]);
- vector32_load(&vals2, &base[i + nelem_per_vector]);
- vector32_load(&vals3, &base[i + nelem_per_vector * 2]);
- vector32_load(&vals4, &base[i + nelem_per_vector * 3]);
-
- /* compare each value to the key */
- result1 = vector32_eq(keys, vals1);
- result2 = vector32_eq(keys, vals2);
- result3 = vector32_eq(keys, vals3);
- result4 = vector32_eq(keys, vals4);
-
- /* combine the results into a single variable */
- tmp1 = vector32_or(result1, result2);
- tmp2 = vector32_or(result3, result4);
- result = vector32_or(tmp1, tmp2);
-
- /* see if there was a match */
- if (vector32_is_highbit_set(result))
+ if (pg_lfind32_helper(keys, &base[i]))
{
Assert(assert_result == true);
return true;
}
- }
+
+ i += nelem_per_iteration;
+
+ } while (i < tail_idx);
+
+ /*
+ * Process the last 'nelem_per_iteration' elements in the array with a
+ * 4-register block. This will cause us to check some of the elements
+ * more than once, but that won't affect correctness, and testing has
+ * demonstrated that this helps more cases than it harms.
+ */
+ Assert(assert_result == pg_lfind32_helper(keys, &base[nelem - nelem_per_iteration]));
+ return pg_lfind32_helper(keys, &base[nelem - nelem_per_iteration]);
+
#endif /* ! USE_NO_SIMD */
+one_by_one:
/* Process the remaining elements one at a time. */
for (; i < nelem; i++)
{
--
2.25.1
--sm4nu43k4a2Rpi4c--
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Fix port/pg_iovec.h building extensions on x86_64-darwin
@ 2024-11-08 20:00 Nathan Bossart <[email protected]>
2024-11-08 21:20 ` Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Nathan Bossart @ 2024-11-08 20:00 UTC (permalink / raw)
To: Wolfgang Walther <[email protected]>; +Cc: [email protected]
On Fri, Nov 08, 2024 at 08:08:06PM +0100, Wolfgang Walther wrote:
> @@ -68,7 +68,7 @@ pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
> }
> sum += part;
> offset += part;
> - if (part < iov[i].iov_len)
> + if ((size_t) part < iov[i].iov_len)
> return sum;
> }
> return sum;
> @@ -107,7 +107,7 @@ pg_pwritev(int fd, const struct iovec *iov, int iovcnt, off_t offset)
> }
> sum += part;
> offset += part;
> - if (part < iov[i].iov_len)
> + if ((size_t) part < iov[i].iov_len)
> return sum;
> }
> return sum;
This looks correct to me. At this point in the code, we know that part >=
0, so casting it to an unsigned long ought to be okay.
--
nathan
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Fix port/pg_iovec.h building extensions on x86_64-darwin
2024-11-08 20:00 Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
@ 2024-11-08 21:20 ` Nathan Bossart <[email protected]>
2024-11-08 22:15 ` Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Nathan Bossart @ 2024-11-08 21:20 UTC (permalink / raw)
To: Wolfgang Walther <[email protected]>; +Cc: [email protected]
Here is a new version of the patch with an updated commit message. The
cfbot results [0] look good, so I plan to commit this one shortly unless
someone objects.
[0] https://cirrus-ci.com/build/6599760059039744
--
nathan
From 5e7156defd3a169323e2bc354c3a3c4cb232fa67 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <[email protected]>
Date: Fri, 8 Nov 2024 15:16:41 -0600
Subject: [PATCH v2 1/1] Fix sign-compare warnings in pg_iovec.h.
The code in question (pg_preadv() and pg_pwritev()) has been around
for a while, but commit 15c9ac3629 moved it to a header file. If
third-party code that includes this header file is built with
-Wsign-compare on a system without preadv() or pwritev(), warnings
ensue. This commit fixes said warnings by casting the result of
pg_pread()/pg_pwrite() to size_t, which should be safe because we
have already checked for a negative value.
Author: Wolfgang Walther
Discussion: https://postgr.es/m/16989737-1aa8-48fd-8dfe-b7ada06509ab%40technowledgy.de
Backpatch-through: 17
---
src/include/port/pg_iovec.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/include/port/pg_iovec.h b/src/include/port/pg_iovec.h
index 7255c1bd91..e5fe677b37 100644
--- a/src/include/port/pg_iovec.h
+++ b/src/include/port/pg_iovec.h
@@ -68,7 +68,7 @@ pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
}
sum += part;
offset += part;
- if (part < iov[i].iov_len)
+ if ((size_t) part < iov[i].iov_len)
return sum;
}
return sum;
@@ -107,7 +107,7 @@ pg_pwritev(int fd, const struct iovec *iov, int iovcnt, off_t offset)
}
sum += part;
offset += part;
- if (part < iov[i].iov_len)
+ if ((size_t) part < iov[i].iov_len)
return sum;
}
return sum;
--
2.39.5 (Apple Git-154)
Attachments:
[text/plain] v2-0001-Fix-sign-compare-warnings-in-pg_iovec.h.patch (1.5K, ../../Zy6AgDqqZTlTD3e_@nathan/2-v2-0001-Fix-sign-compare-warnings-in-pg_iovec.h.patch)
download | inline diff:
From 5e7156defd3a169323e2bc354c3a3c4cb232fa67 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <[email protected]>
Date: Fri, 8 Nov 2024 15:16:41 -0600
Subject: [PATCH v2 1/1] Fix sign-compare warnings in pg_iovec.h.
The code in question (pg_preadv() and pg_pwritev()) has been around
for a while, but commit 15c9ac3629 moved it to a header file. If
third-party code that includes this header file is built with
-Wsign-compare on a system without preadv() or pwritev(), warnings
ensue. This commit fixes said warnings by casting the result of
pg_pread()/pg_pwrite() to size_t, which should be safe because we
have already checked for a negative value.
Author: Wolfgang Walther
Discussion: https://postgr.es/m/16989737-1aa8-48fd-8dfe-b7ada06509ab%40technowledgy.de
Backpatch-through: 17
---
src/include/port/pg_iovec.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/include/port/pg_iovec.h b/src/include/port/pg_iovec.h
index 7255c1bd91..e5fe677b37 100644
--- a/src/include/port/pg_iovec.h
+++ b/src/include/port/pg_iovec.h
@@ -68,7 +68,7 @@ pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
}
sum += part;
offset += part;
- if (part < iov[i].iov_len)
+ if ((size_t) part < iov[i].iov_len)
return sum;
}
return sum;
@@ -107,7 +107,7 @@ pg_pwritev(int fd, const struct iovec *iov, int iovcnt, off_t offset)
}
sum += part;
offset += part;
- if (part < iov[i].iov_len)
+ if ((size_t) part < iov[i].iov_len)
return sum;
}
return sum;
--
2.39.5 (Apple Git-154)
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Fix port/pg_iovec.h building extensions on x86_64-darwin
2024-11-08 20:00 Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
2024-11-08 21:20 ` Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
@ 2024-11-08 22:15 ` Nathan Bossart <[email protected]>
0 siblings, 0 replies; 4+ messages in thread
From: Nathan Bossart @ 2024-11-08 22:15 UTC (permalink / raw)
To: Wolfgang Walther <[email protected]>; +Cc: [email protected]
On Fri, Nov 08, 2024 at 03:20:00PM -0600, Nathan Bossart wrote:
> Here is a new version of the patch with an updated commit message. The
> cfbot results [0] look good, so I plan to commit this one shortly unless
> someone objects.
Committed.
--
nathan
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2024-11-08 22:15 UTC | newest]
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2024-03-20 19:20 [PATCH v7 1/1] pg_lfind32(): add "overlap" code for remaining elements Nathan Bossart <[email protected]>
2024-11-08 20:00 Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
2024-11-08 21:20 ` Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
2024-11-08 22:15 ` Re: Fix port/pg_iovec.h building extensions on x86_64-darwin Nathan Bossart <[email protected]>
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