From 064ba8cc9f429fbf403f8d2c564e5f59f6799df9 Mon Sep 17 00:00:00 2001 From: Daniel Black Date: Fri, 17 Nov 2017 08:00:32 +0800 Subject: [PATCH] item_cmp_type: simplier for a faster codepath The common case for this function is that both types are the same. The Item_result defination from include/mysql.h.pp is the following enum enum Item_result { STRING_RESULT=0, REAL_RESULT, INT_RESULT, ROW_RESULT, DECIMAL_RESULT, TIME_RESULT }; The compilers aren't quite smart enough to optimize to this shortcut so this makes it quicker. Before the change: 0000000000012730 : 12730: 89 f0 mov %esi,%eax 12732: 09 f8 or %edi,%eax 12734: 74 4c je 12782 12736: 83 ff 02 cmp $0x2,%edi 12739: 75 0a jne 12745 1273b: b8 02 00 00 00 mov $0x2,%eax 12740: 83 fe 02 cmp $0x2,%esi 12743: 74 3c je 12781 12745: 83 ff 03 cmp $0x3,%edi 12748: b8 03 00 00 00 mov $0x3,%eax 1274d: 74 32 je 12781 1274f: 83 fe 03 cmp $0x3,%esi 12752: 74 2d je 12781 12754: 83 ff 05 cmp $0x5,%edi 12757: b8 05 00 00 00 mov $0x5,%eax 1275c: 74 23 je 12781 1275e: 83 fe 05 cmp $0x5,%esi 12761: 74 1e je 12781 12763: 83 ff 04 cmp $0x4,%edi 12766: 74 05 je 1276d 12768: 83 ff 02 cmp $0x2,%edi 1276b: 75 0f jne 1277c 1276d: b8 04 00 00 00 mov $0x4,%eax 12772: 83 fe 02 cmp $0x2,%esi 12775: 74 0a je 12781 12777: 83 fe 04 cmp $0x4,%esi 1277a: 74 05 je 12781 1277c: b8 01 00 00 00 mov $0x1,%eax 12781: c3 retq 12782: 31 c0 xor %eax,%eax 12784: c3 retq After, noting the short cut and the beginning of the function: 0000000000012730 : 12730: 39 f7 cmp %esi,%edi 12732: 75 03 jne 12737 12734: 89 f8 mov %edi,%eax 12736: c3 retq 12737: 83 ff 03 cmp $0x3,%edi 1273a: b8 03 00 00 00 mov $0x3,%eax 1273f: 74 32 je 12773 12741: 83 fe 03 cmp $0x3,%esi 12744: 74 2d je 12773 12746: 83 ff 05 cmp $0x5,%edi 12749: b8 05 00 00 00 mov $0x5,%eax 1274e: 74 23 je 12773 12750: 83 fe 05 cmp $0x5,%esi 12753: 74 1e je 12773 12755: 83 ff 04 cmp $0x4,%edi 12758: 74 05 je 1275f 1275a: 83 ff 02 cmp $0x2,%edi 1275d: 75 0f jne 1276e 1275f: b8 04 00 00 00 mov $0x4,%eax 12764: 83 fe 02 cmp $0x2,%esi 12767: 74 0a je 12773 12769: 83 fe 04 cmp $0x4,%esi 1276c: 74 05 je 12773 1276e: b8 01 00 00 00 mov $0x1,%eax 12773: c3 retq Signed-off-by: Daniel Black --- sql/item.cc | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/sql/item.cc b/sql/item.cc index 0cf4864326f..745cbf31f0c 100644 --- a/sql/item.cc +++ b/sql/item.cc @@ -8719,13 +8719,11 @@ void Item_trigger_field::cleanup() Item_result item_cmp_type(Item_result a,Item_result b) { - if (a == STRING_RESULT && b == STRING_RESULT) - return STRING_RESULT; - if (a == INT_RESULT && b == INT_RESULT) - return INT_RESULT; - else if (a == ROW_RESULT || b == ROW_RESULT) + if (a == b) + return a; + if (a == ROW_RESULT || b == ROW_RESULT) return ROW_RESULT; - else if (a == TIME_RESULT || b == TIME_RESULT) + if (a == TIME_RESULT || b == TIME_RESULT) return TIME_RESULT; if ((a == INT_RESULT || a == DECIMAL_RESULT) && (b == INT_RESULT || b == DECIMAL_RESULT))