golang/go

cmd/compile: doesn't optimize float comparison to MINSD

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#72,831 建立於 2025年3月12日

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 (11 留言) (3 反應) (0 負責人)Go (133,883 star) (19,008 fork)batch import
BugReportNeedsFixPerformancecompiler/runtimehelp wanted

描述

Go version

go version go1.24.1 linux/amd64

Output of go env in your module/workspace:

-

What did you do?

go build -gcflags=-S

func mymin(a, b float64) float64 {
	if a < b {
		return a
	} else {
		return b
	}
}

What did you see happen?

0x0000 00000 (bar.go:4)      UCOMISD X0, X1
0x0004 00004 (bar.go:4)      JLS     7
0x0006 00006 (bar.go:5)      RET
0x0007 00007 (bar.go:7)      MOVUPS  X1, X0
0x000a 00010 (bar.go:7)      RET

What did you expect to see?

I think

MINSD X1, X0
RET

but maybe

MINSD X0, X1
MOVUPS X1, X0
RET

AT&T argument order has me thoroughly confused at times.

貢獻者指南

技術棧
go
領域
performance
議題類型
performance
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
5
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
over 1 week
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
active
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Go compiler internalsx86 assemblySSA form
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
10
研究方向
Investigate the Go SSA compiler backend in cmd/compile/internal/ssa for x86 architecture to add a rule that replaces a float comparison followed by conditional move with MINSD instruction. The current code generates UCOMISD and JLS; the optimization should detect this pattern and emit MINSD. Review similar optimization rules for MINSS and MAXSS for float32. Also check the issue comments for additional context.