cmd/compile/internal/gc: better inliner diagnostics

When debugging inliner with -m -m print cost of complex functions,
instead of simple "function too complex". This helps to understand,
how close to inlining is this particular function.

Change-Id: I6871f69b5b914d23fd0b43a24d7c6fc928f4b716
Reviewed-on: https://go-review.googlesource.com/63330
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/gc/inl.go b/src/cmd/compile/internal/gc/inl.go
index 3a34ab9246c60f869994dd207ddd780c378f345d..35da0de6ddbad3ac3cb453de432527c8dd7d412f 100644 (file)
--- a/src/cmd/compile/internal/gc/inl.go
+++ b/src/cmd/compile/internal/gc/inl.go
@@ -157,7 +157,7 @@ func caninl(fn *Node) {
                return
        }
        if visitor.budget < 0 {
-               reason = "function too complex"
+               reason = fmt.Sprintf("function too complex: cost %d exceeds budget %d", maxBudget-visitor.budget, maxBudget)
                return
        }
 
@@ -297,8 +297,8 @@ func (v *hairyVisitor) visit(n *Node) bool {
                v.budget -= 2
        }
 
-       if v.budget < 0 {
-               v.reason = "function too complex"
+       // When debugging, don't stop early, to get full cost of inlining this function
+       if v.budget < 0 && Debug['m'] < 2 {
                return true
        }