cmd/compile: //go:norace should prohibit inlining into functions that will be instrumented

[mdempsky]

Currently, compiling this package:

package p

func F(p *int) { g(p) }

//go:norace
func g(p *int) { *p = 0 }

with "-S -race" shows that g is inlined into F, and the pointer assignment is instrumented with a race detector call, which seemingly defeats the intention of adding //go:norace.

Probably the easiest solution is that when instrumenting, we should treat //go:norace functions as non-inlinable.

Even better would be to avoid inlining //go:norace function calls only into instrumented functions (similar to how CL 102815 still allows inlining runtime calls within package runtime even during instrumented builds), but that would require tracking the //go:norace pragma across compilation units, which is a bit more involved.

/cc @cherrymui

[gopherbot]

Change https://golang.org/cl/119195 mentions this issue: cmd/compile: conditional on -race, disable inline of go:norace