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runtime: floating-point comparison error on Loong64 #59000

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ihuang77 opened this issue Mar 13, 2023 · 3 comments
Closed

runtime: floating-point comparison error on Loong64 #59000

ihuang77 opened this issue Mar 13, 2023 · 3 comments
Labels
arch-loong64 Issues solely affecting the loongson architecture. compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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@ihuang77
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What version of Go are you using (go version)?

$ go version
go version devel go1.21-f5c7416511 Thu Mar 9 22:13:26 2023 +0000 linux/loong64

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

go env Output
$ go env

What did you do?

package main

import(
        "fmt"
)

func main() {
        var target float64 = 100000.0
        for i := 1; i < 100000000; i++ {
                var fslice []float64
                for j := 0; j < 100; j++ {
                        fslice = append(fslice, 1.124567)
                }
                var sum float64
                for _, f := range fslice {
                        sum += f
                        sum += 0.1 
                        sum += 0.2 
                        sum += 0.3 
                        if sum >= target {
                                fmt.Println("err 1")
                        }
                        if sum >= target {
                                fmt.Println("err 2")
                        }
                        if sum >= target {
                                fmt.Println("err 3")
                        }
                        if sum >= target {
                                if sum < target {
                                        fmt.Println("err 4")
                                }
                        }
                }
        }
}

What did you expect to see?

(i.e. no output)

What did you see instead?

err 3
err 4
err 2
...

(i.e. numbers are unordered)

@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Mar 13, 2023
@gopherbot
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Change https://go.dev/cl/475577 mentions this issue: runtime: save and restore fcc registers in async preempt on loong64

@abner-chenc abner-chenc added the arch-loong64 Issues solely affecting the loongson architecture. label Mar 13, 2023
@cherrymui cherrymui changed the title cmd/internal/obj/loong64, runtime:Fixed a floating-point comparison error runtime: floating-point comparison error on Loong64 Mar 13, 2023
@cherrymui cherrymui added the NeedsFix The path to resolution is known, but the work has not been done. label Mar 13, 2023
@cherrymui cherrymui added this to the Go1.21 milestone Mar 13, 2023
@mknyszek
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CC @golang/loong64

gopherbot pushed a commit that referenced this issue Mar 22, 2023
During the context switch of goroutine scheduling, the value of the
fcc0 register needs to be saved on the stack.

Fixs #59000.

Change-Id: Ie80dbae738f60df6c11a3fe31fc57de817d76afc
Reviewed-on: https://go-review.googlesource.com/c/go/+/475577
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: WANG Xuerui <git@xen0n.name>
@xen0n
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xen0n commented Mar 23, 2023

Commit 48d61a4 had the "Fixes" keyword misspelled, so the issue was not auto-closed.

Manually closing as completed.

@xen0n xen0n closed this as completed Mar 23, 2023
xen0n pushed a commit to xen0n/go that referenced this issue May 1, 2023
During the context switch of goroutine scheduling, the value of the
fcc0 register needs to be saved on the stack.

Fixs golang#59000.

Change-Id: Ie80dbae738f60df6c11a3fe31fc57de817d76afc
Reviewed-on: https://go-review.googlesource.com/c/go/+/475577
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: WANG Xuerui <git@xen0n.name>
(cherry picked from commit 48d61a4)
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Labels
arch-loong64 Issues solely affecting the loongson architecture. compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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