Date: Thu, 26 Sep 2024 15:17:03 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: pgsql-hackers@postgresql.org
Subject: micro-optimize nbtcompare.c routines
Message-ID: <ZvXBP3Rbfmris0yf@nathan>
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Here's a patch that adjusts several routines in nbtcompare.c and related
files to use the branchless integer comparison functions added in commit
6b80394.  It's probably unlikely this produces a measurable benefit (at
least I've been unable to find any in my admittedly-limited testing), but
in theory it should save a cycle here and there.  I was hoping that this
would trim many lines of code, but maintaining the STRESS_SORT_INT_MIN
stuff eats up most of what we save.

Anyway, I don't feel too strongly about this patch, but I went to the
trouble of writing it, and so I figured I'd post it.

-- 
nathan

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	filename="v1-0001-micro-optimize-nbtcompare.c-routines.patch"

From bd2e1eb92b28cf855b529b09813f1b09084c7cfc Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Thu, 26 Sep 2024 15:03:32 -0500
Subject: [PATCH v1 1/1] micro-optimize nbtcompare.c routines

---
 src/backend/access/nbtree/nbtcompare.c | 162 ++++++++++++-------------
 src/backend/storage/page/itemptr.c     |  18 +--
 src/backend/utils/sort/tuplesort.c     |  21 ++--
 3 files changed, 96 insertions(+), 105 deletions(-)

diff --git a/src/backend/access/nbtree/nbtcompare.c b/src/backend/access/nbtree/nbtcompare.c
index 1c72867c84..2df0c5dbe0 100644
--- a/src/backend/access/nbtree/nbtcompare.c
+++ b/src/backend/access/nbtree/nbtcompare.c
@@ -57,17 +57,16 @@
 
 #include <limits.h>
 
+#include "common/int.h"
 #include "utils/fmgrprotos.h"
 #include "utils/sortsupport.h"
 
-#ifdef STRESS_SORT_INT_MIN
-#define A_LESS_THAN_B		INT_MIN
-#define A_GREATER_THAN_B	INT_MAX
-#else
-#define A_LESS_THAN_B		(-1)
-#define A_GREATER_THAN_B	1
-#endif
-
+#define STRESS_SORT_INT_MIN_CMP(a, b) \
+( \
+	((a) > (b)) ? INT_MAX : \
+	((a) < (b)) ? INT_MIN : \
+	0 \
+)
 
 Datum
 btboolcmp(PG_FUNCTION_ARGS)
@@ -84,7 +83,11 @@ btint2cmp(PG_FUNCTION_ARGS)
 	int16		a = PG_GETARG_INT16(0);
 	int16		b = PG_GETARG_INT16(1);
 
-	PG_RETURN_INT32((int32) a - (int32) b);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s16(a, b));
+#endif
 }
 
 static int
@@ -93,7 +96,11 @@ btint2fastcmp(Datum x, Datum y, SortSupport ssup)
 	int16		a = DatumGetInt16(x);
 	int16		b = DatumGetInt16(y);
 
-	return (int) a - (int) b;
+#ifdef STRESS_SORT_INT_MIN
+	return STRESS_SORT_INT_MIN_CMP(a, b);
+#else
+	return pg_cmp_s16(a, b);
+#endif
 }
 
 Datum
@@ -111,12 +118,11 @@ btint4cmp(PG_FUNCTION_ARGS)
 	int32		a = PG_GETARG_INT32(0);
 	int32		b = PG_GETARG_INT32(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s32(a, b));
+#endif
 }
 
 Datum
@@ -134,12 +140,11 @@ btint8cmp(PG_FUNCTION_ARGS)
 	int64		a = PG_GETARG_INT64(0);
 	int64		b = PG_GETARG_INT64(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s64(a, b));
+#endif
 }
 
 #if SIZEOF_DATUM < 8
@@ -149,12 +154,11 @@ btint8fastcmp(Datum x, Datum y, SortSupport ssup)
 	int64		a = DatumGetInt64(x);
 	int64		b = DatumGetInt64(y);
 
-	if (a > b)
-		return A_GREATER_THAN_B;
-	else if (a == b)
-		return 0;
-	else
-		return A_LESS_THAN_B;
+#ifdef STRESS_SORT_INT_MIN
+	return STRESS_SORT_INT_MIN_CMP(a, b);
+#else
+	return pg_cmp_s64(a, b);
+#endif
 }
 #endif
 
@@ -177,12 +181,11 @@ btint48cmp(PG_FUNCTION_ARGS)
 	int32		a = PG_GETARG_INT32(0);
 	int64		b = PG_GETARG_INT64(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s64(a, b));
+#endif
 }
 
 Datum
@@ -191,12 +194,11 @@ btint84cmp(PG_FUNCTION_ARGS)
 	int64		a = PG_GETARG_INT64(0);
 	int32		b = PG_GETARG_INT32(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s64(a, b));
+#endif
 }
 
 Datum
@@ -205,12 +207,11 @@ btint24cmp(PG_FUNCTION_ARGS)
 	int16		a = PG_GETARG_INT16(0);
 	int32		b = PG_GETARG_INT32(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s32(a, b));
+#endif
 }
 
 Datum
@@ -219,12 +220,11 @@ btint42cmp(PG_FUNCTION_ARGS)
 	int32		a = PG_GETARG_INT32(0);
 	int16		b = PG_GETARG_INT16(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s32(a, b));
+#endif
 }
 
 Datum
@@ -233,12 +233,11 @@ btint28cmp(PG_FUNCTION_ARGS)
 	int16		a = PG_GETARG_INT16(0);
 	int64		b = PG_GETARG_INT64(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s64(a, b));
+#endif
 }
 
 Datum
@@ -247,12 +246,11 @@ btint82cmp(PG_FUNCTION_ARGS)
 	int64		a = PG_GETARG_INT64(0);
 	int16		b = PG_GETARG_INT16(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_s64(a, b));
+#endif
 }
 
 Datum
@@ -261,12 +259,11 @@ btoidcmp(PG_FUNCTION_ARGS)
 	Oid			a = PG_GETARG_OID(0);
 	Oid			b = PG_GETARG_OID(1);
 
-	if (a > b)
-		PG_RETURN_INT32(A_GREATER_THAN_B);
-	else if (a == b)
-		PG_RETURN_INT32(0);
-	else
-		PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+	PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(a, b));
+#else
+	PG_RETURN_INT32(pg_cmp_u32(a, b));
+#endif
 }
 
 static int
@@ -275,12 +272,11 @@ btoidfastcmp(Datum x, Datum y, SortSupport ssup)
 	Oid			a = DatumGetObjectId(x);
 	Oid			b = DatumGetObjectId(y);
 
-	if (a > b)
-		return A_GREATER_THAN_B;
-	else if (a == b)
-		return 0;
-	else
-		return A_LESS_THAN_B;
+#ifdef STRESS_SORT_INT_MIN
+	return STRESS_SORT_INT_MIN_CMP(a, b);
+#else
+	return pg_cmp_u32(a, b);
+#endif
 }
 
 Datum
@@ -305,12 +301,16 @@ btoidvectorcmp(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < a->dim1; i++)
 	{
-		if (a->values[i] != b->values[i])
+		Oid			aval = a->values[i];
+		Oid			bval = b->values[i];
+
+		if (aval != bval)
 		{
-			if (a->values[i] > b->values[i])
-				PG_RETURN_INT32(A_GREATER_THAN_B);
-			else
-				PG_RETURN_INT32(A_LESS_THAN_B);
+#ifdef STRESS_SORT_INT_MIN
+			PG_RETURN_INT32(STRESS_SORT_INT_MIN_CMP(aval, bval));
+#else
+			PG_RETURN_INT32(pg_cmp_u32(aval, bval));
+#endif
 		}
 	}
 	PG_RETURN_INT32(0);
diff --git a/src/backend/storage/page/itemptr.c b/src/backend/storage/page/itemptr.c
index af21170307..d85592951e 100644
--- a/src/backend/storage/page/itemptr.c
+++ b/src/backend/storage/page/itemptr.c
@@ -14,6 +14,7 @@
  */
 #include "postgres.h"
 
+#include "common/int.h"
 #include "storage/itemptr.h"
 
 
@@ -57,18 +58,11 @@ ItemPointerCompare(ItemPointer arg1, ItemPointer arg2)
 	BlockNumber b1 = ItemPointerGetBlockNumberNoCheck(arg1);
 	BlockNumber b2 = ItemPointerGetBlockNumberNoCheck(arg2);
 
-	if (b1 < b2)
-		return -1;
-	else if (b1 > b2)
-		return 1;
-	else if (ItemPointerGetOffsetNumberNoCheck(arg1) <
-			 ItemPointerGetOffsetNumberNoCheck(arg2))
-		return -1;
-	else if (ItemPointerGetOffsetNumberNoCheck(arg1) >
-			 ItemPointerGetOffsetNumberNoCheck(arg2))
-		return 1;
-	else
-		return 0;
+	if (b1 != b2)
+		return pg_cmp_u32(b1, b2);
+
+	return pg_cmp_u16(ItemPointerGetOffsetNumberNoCheck(arg1),
+					  ItemPointerGetOffsetNumberNoCheck(arg2));
 }
 
 /*
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index c960cfa823..ec1ff3e656 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -102,6 +102,7 @@
 #include <limits.h>
 
 #include "commands/tablespace.h"
+#include "common/int.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
 #include "storage/shmem.h"
@@ -3138,12 +3139,18 @@ free_sort_tuple(Tuplesortstate *state, SortTuple *stup)
 int
 ssup_datum_unsigned_cmp(Datum x, Datum y, SortSupport ssup)
 {
+#if SIZEOF_DATUM == 4
+	return pg_cmp_u32(x, y);
+#elif SIZEOF_DATUM == 8
+	return pg_cmp_u64(x, y);
+#else
 	if (x < y)
 		return -1;
 	else if (x > y)
 		return 1;
 	else
 		return 0;
+#endif
 }
 
 #if SIZEOF_DATUM >= 8
@@ -3153,12 +3160,7 @@ ssup_datum_signed_cmp(Datum x, Datum y, SortSupport ssup)
 	int64		xx = DatumGetInt64(x);
 	int64		yy = DatumGetInt64(y);
 
-	if (xx < yy)
-		return -1;
-	else if (xx > yy)
-		return 1;
-	else
-		return 0;
+	return pg_cmp_s64(xx, yy);
 }
 #endif
 
@@ -3168,10 +3170,5 @@ ssup_datum_int32_cmp(Datum x, Datum y, SortSupport ssup)
 	int32		xx = DatumGetInt32(x);
 	int32		yy = DatumGetInt32(y);
 
-	if (xx < yy)
-		return -1;
-	else if (xx > yy)
-		return 1;
-	else
-		return 0;
+	return pg_cmp_s32(xx, yy);
 }
-- 
2.39.5 (Apple Git-154)


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