From: David Chase <drchase@google.com>
Date: Wed, 2 Nov 2022 21:21:09 +0000 (-0400)
Subject: cmd/compile: tweak compiler concurrency
X-Git-Tag: go1.20rc1~419
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b725622ceb3d537334e1a3bb1723b1e939a40823;p=gostls13.git

cmd/compile: tweak compiler concurrency

Default concurrency is now GOMAXPROCS, though this is normally
reduced to 4 by the go build commmand.

If compiler flags don't permit concurrency, silently
turn it down instead of failing the compilation.

Change-Id: Id26cc3214e0ca402d60f915e98276a58d809e097
Reviewed-on: https://go-review.googlesource.com/c/go/+/447358
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
---

diff --git a/src/cmd/compile/internal/base/flag.go b/src/cmd/compile/internal/base/flag.go
index 6d2847bc06..eb346e29fc 100644
--- a/src/cmd/compile/internal/base/flag.go
+++ b/src/cmd/compile/internal/base/flag.go
@@ -147,7 +147,7 @@ type CmdFlags struct {
 func ParseFlags() {
 	Flag.I = addImportDir
 
-	Flag.LowerC = 1
+	Flag.LowerC = runtime.GOMAXPROCS(0)
 	Flag.LowerD = objabi.NewDebugFlag(&Debug, DebugSSA)
 	Flag.LowerP = &Ctxt.Pkgpath
 	Flag.LowerV = &Ctxt.Debugvlog
@@ -267,8 +267,8 @@ func ParseFlags() {
 	if Flag.LowerC < 1 {
 		log.Fatalf("-c must be at least 1, got %d", Flag.LowerC)
 	}
-	if Flag.LowerC > 1 && !concurrentBackendAllowed() {
-		log.Fatalf("cannot use concurrent backend compilation with provided flags; invoked as %v", os.Args)
+	if !concurrentBackendAllowed() {
+		Flag.LowerC = 1
 	}
 
 	if Flag.CompilingRuntime {