From 8098b99547e2bb802c976a424e486ba94d3222a8 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Wed, 20 Aug 2025 16:53:09 -0700 Subject: [PATCH] internal/runtime/maps: speed up Clear We don't need to know the actual full slots, just whether there are any or not. The test for any full slots is simpler on amd64. We don't have to use PMOVMSKB and do the intreg->floatreg transfer. Fixes #75097 Change-Id: Iace1c100618d7fc2ac5ddd5fe9e8fe5c9595243f Reviewed-on: https://go-review.googlesource.com/c/go/+/697875 Reviewed-by: Youlin Feng Auto-Submit: Keith Randall LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Pratt Reviewed-by: Keith Randall --- src/internal/runtime/maps/group.go | 6 ++++++ src/internal/runtime/maps/table.go | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/src/internal/runtime/maps/group.go b/src/internal/runtime/maps/group.go index c8d38ba27c..a56d32aca0 100644 --- a/src/internal/runtime/maps/group.go +++ b/src/internal/runtime/maps/group.go @@ -215,6 +215,12 @@ func (g ctrlGroup) matchFull() bitset { return ctrlGroupMatchFull(g) } +// anyFull reports whether any slots in the group are full. +func (g ctrlGroup) anyFull() bool { + // A slot is full iff bit 7 is unset. Test whether any slot has bit 7 unset. + return (^g)&bitsetMSB != 0 +} + // Portable implementation of matchFull. // // Note: On AMD64, this is an intrinsic implemented with SIMD instructions. See diff --git a/src/internal/runtime/maps/table.go b/src/internal/runtime/maps/table.go index 49f392b8ae..a8160befd2 100644 --- a/src/internal/runtime/maps/table.go +++ b/src/internal/runtime/maps/table.go @@ -606,7 +606,7 @@ func (t *table) Clear(typ *abi.MapType) { } for i := uint64(0); i <= t.groups.lengthMask; i++ { g := t.groups.group(typ, i) - if g.ctrls().matchFull() != 0 { + if g.ctrls().anyFull() { typedmemclr(typ.Group, g.data) } g.ctrls().setEmpty() -- 2.52.0