From 5239c913510633ce9fdfaf993ab5f31d7ba7e83e Mon Sep 17 00:00:00 2001
From: Than McIntosh <thanm@google.com>
Date: Fri, 3 Nov 2023 14:04:57 -0400
Subject: [PATCH] cmd/compile/internal/inline: minor compile time improvements
 in func flags

Some small changes to help reduce compile time for function flags
computation. The current implementation of panic path detection adds
an entry to a map for every node in the function, which is wasteful
(and shows up in cpu profiles). Switch to only adding entries where
they are useful. This is especially important for functions with large
map literals and other constructs with many non-statement nodes.

Change-Id: I9cfb2cd1cbf480f21298e6102aa99e2d77219f3d
Reviewed-on: https://go-review.googlesource.com/c/go/+/539696
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 .../inline/inlheur/analyze_func_flags.go      | 32 ++++++-------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/src/cmd/compile/internal/inline/inlheur/analyze_func_flags.go b/src/cmd/compile/internal/inline/inlheur/analyze_func_flags.go
index 588d2f4f59..b7403a4f8c 100644
--- a/src/cmd/compile/internal/inline/inlheur/analyze_func_flags.go
+++ b/src/cmd/compile/internal/inline/inlheur/analyze_func_flags.go
@@ -66,34 +66,24 @@ func (ffa *funcFlagsAnalyzer) setResults(funcProps *FuncProps) {
 	funcProps.Flags = rv
 }
 
-func (ffa *funcFlagsAnalyzer) getstate(n ir.Node) pstate {
-	val, ok := ffa.nstate[n]
-	if !ok {
-		base.Fatalf("funcFlagsAnalyzer: fn %q node %s line %s: internal error, no setting for node:\n%+v\n", ffa.fn.Sym().Name, n.Op().String(), ir.Line(n), n)
-	}
-	return val
+func (ffa *funcFlagsAnalyzer) getState(n ir.Node) pstate {
+	return ffa.nstate[n]
 }
 
-func (ffa *funcFlagsAnalyzer) setstate(n ir.Node, st pstate) {
-	if _, ok := ffa.nstate[n]; ok {
-		base.Fatalf("funcFlagsAnalyzer: fn %q internal error, existing setting for node:\n%+v\n", ffa.fn.Sym().Name, n)
-	} else {
+func (ffa *funcFlagsAnalyzer) setState(n ir.Node, st pstate) {
+	if st != psNoInfo {
 		ffa.nstate[n] = st
 	}
 }
 
-func (ffa *funcFlagsAnalyzer) updatestate(n ir.Node, st pstate) {
-	if _, ok := ffa.nstate[n]; !ok {
-		base.Fatalf("funcFlagsAnalyzer: fn %q internal error, expected existing setting for node:\n%+v\n", ffa.fn.Sym().Name, n)
+func (ffa *funcFlagsAnalyzer) updateState(n ir.Node, st pstate) {
+	if st == psNoInfo {
+		delete(ffa.nstate, n)
 	} else {
 		ffa.nstate[n] = st
 	}
 }
 
-func (ffa *funcFlagsAnalyzer) setstateSoft(n ir.Node, st pstate) {
-	ffa.nstate[n] = st
-}
-
 func (ffa *funcFlagsAnalyzer) panicPathTable() map[ir.Node]pstate {
 	return ffa.nstate
 }
@@ -164,13 +154,13 @@ func (ffa *funcFlagsAnalyzer) stateForList(list ir.Nodes) pstate {
 	// line 10 will be on a panic path).
 	for i := len(list) - 1; i >= 0; i-- {
 		n := list[i]
-		psi := ffa.getstate(n)
+		psi := ffa.getState(n)
 		if debugTrace&debugTraceFuncFlags != 0 {
 			fmt.Fprintf(os.Stderr, "=-= %v: stateForList n=%s ps=%s\n",
 				ir.Line(n), n.Op().String(), psi.String())
 		}
 		st = blockCombine(psi, st)
-		ffa.updatestate(n, st)
+		ffa.updateState(n, st)
 	}
 	if st == psTop {
 		st = psNoInfo
@@ -237,8 +227,6 @@ func (ffa *funcFlagsAnalyzer) nodeVisitPost(n ir.Node) {
 			ir.Line(n), n.Op().String(), shouldVisit(n))
 	}
 	if !shouldVisit(n) {
-		// invoke soft set, since node may be shared (e.g. ONAME)
-		ffa.setstateSoft(n, psNoInfo)
 		return
 	}
 	var st pstate
@@ -361,7 +349,7 @@ func (ffa *funcFlagsAnalyzer) nodeVisitPost(n ir.Node) {
 		fmt.Fprintf(os.Stderr, "=-= %v: visit n=%s returns %s\n",
 			ir.Line(n), n.Op().String(), st.String())
 	}
-	ffa.setstate(n, st)
+	ffa.setState(n, st)
 }
 
 func (ffa *funcFlagsAnalyzer) nodeVisitPre(n ir.Node) {