From 07749aef988e55aba0c67aeb3607f42b58d4e249 Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Mon, 21 Mar 2016 10:52:03 -0700 Subject: [PATCH] cmd/compile: special-case const comparisons against zero Constant comparisons against 0 are reasonably common. Special-case and avoid allocating a new zero value each time. Change-Id: I6c526c8ab30ef7f0fef59110133c764b7b90ba05 Reviewed-on: https://go-review.googlesource.com/20956 Reviewed-by: Alan Donovan --- src/cmd/compile/internal/gc/mpfloat.go | 10 +++++----- src/cmd/compile/internal/gc/mpint.go | 7 +++++-- src/cmd/compile/internal/gc/walk.go | 4 +--- 3 files changed, 11 insertions(+), 10 deletions(-) diff --git a/src/cmd/compile/internal/gc/mpfloat.go b/src/cmd/compile/internal/gc/mpfloat.go index ca290d70d5..72cc540556 100644 --- a/src/cmd/compile/internal/gc/mpfloat.go +++ b/src/cmd/compile/internal/gc/mpfloat.go @@ -116,11 +116,11 @@ func (a *Mpflt) Cmp(b *Mpflt) int { return a.Val.Cmp(&b.Val) } -func (b *Mpflt) CmpFloat64(c float64) int { - var a Mpflt - - a.SetFloat64(c) - return b.Cmp(&a) +func (a *Mpflt) CmpFloat64(c float64) int { + if c == 0 { + return a.Val.Sign() // common case shortcut + } + return a.Val.Cmp(big.NewFloat(c)) } func (a *Mpflt) Float64() float64 { diff --git a/src/cmd/compile/internal/gc/mpint.go b/src/cmd/compile/internal/gc/mpint.go index 1ab060ee75..d0f87deb00 100644 --- a/src/cmd/compile/internal/gc/mpint.go +++ b/src/cmd/compile/internal/gc/mpint.go @@ -262,8 +262,11 @@ func (a *Mpint) Cmp(b *Mpint) int { return a.Val.Cmp(&b.Val) } -func (b *Mpint) CmpInt64(c int64) int { - return b.Val.Cmp(big.NewInt(c)) +func (a *Mpint) CmpInt64(c int64) int { + if c == 0 { + return a.Val.Sign() // common case shortcut + } + return a.Val.Cmp(big.NewInt(c)) } func (a *Mpint) Neg() { diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go index 428d309722..7a82a808e8 100644 --- a/src/cmd/compile/internal/gc/walk.go +++ b/src/cmd/compile/internal/gc/walk.go @@ -10,8 +10,6 @@ import ( "strings" ) -var mpzero Mpint - // The constant is known to runtime. const ( tmpstringbufsize = 32 @@ -1229,7 +1227,7 @@ opswitch: } if Isconst(n.Right, CTINT) { - if n.Right.Val().U.(*Mpint).Cmp(&mpzero) < 0 || n.Right.Val().U.(*Mpint).Cmp(Maxintval[TINT]) > 0 { + if n.Right.Val().U.(*Mpint).CmpInt64(0) < 0 || n.Right.Val().U.(*Mpint).Cmp(Maxintval[TINT]) > 0 { Yyerror("index out of bounds") } } -- 2.48.1