cmd/compile: move v.Pos.line check to warnRule

This simplifies the rewrite rules.

Change-Id: Iff062297d42a23cb31ad55e8c733842ecbc07da2
Reviewed-on: https://go-review.googlesource.com/129377
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -1363,12 +1363,12 @@
 (NilCheck (Load (OffPtr [c] (SP)) (StaticCall {sym} _)) _)
 	&& isSameSym(sym, "runtime.newobject")
 	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	&& warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")
+	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
 	-> (Invalid)
 (NilCheck (OffPtr (Load (OffPtr [c] (SP)) (StaticCall {sym} _))) _)
 	&& isSameSym(sym, "runtime.newobject")
 	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	&& warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")
+	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
 	-> (Invalid)
 
 // Evaluate constant address comparisons.

src/cmd/compile/internal/ssa/rewrite.go

@@ -646,11 +646,11 @@ func noteRule(s string) bool {
 	return true
 }
 
-// warnRule generates a compiler debug output with string s when
-// cond is true and the rule is fired.
+// warnRule generates compiler debug output with string s when
+// v is not in autogenerated code, cond is true and the rule has fired.
 func warnRule(cond bool, v *Value, s string) bool {
-	if cond {
-		v.Block.Func.Warnl(v.Pos, s)
+	if pos := v.Pos; pos.Line() > 1 && cond {
+		v.Block.Func.Warnl(pos, s)
 	}
 	return true
 }

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -21412,7 +21412,7 @@ func rewriteValuegeneric_OpNilCheck_0(v *Value) bool {
 		return true
 	}
 	// match: (NilCheck (Load (OffPtr [c] (SP)) (StaticCall {sym} _)) _)
-	// cond: isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")
+	// cond: isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")
 	// result: (Invalid)
 	for {
 		_ = v.Args[1]
@@ -21435,14 +21435,14 @@ func rewriteValuegeneric_OpNilCheck_0(v *Value) bool {
 			break
 		}
 		sym := v_0_1.Aux
-		if !(isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")) {
+		if !(isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
 			break
 		}
 		v.reset(OpInvalid)
 		return true
 	}
 	// match: (NilCheck (OffPtr (Load (OffPtr [c] (SP)) (StaticCall {sym} _))) _)
-	// cond: isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")
+	// cond: isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")
 	// result: (Invalid)
 	for {
 		_ = v.Args[1]
@@ -21469,7 +21469,7 @@ func rewriteValuegeneric_OpNilCheck_0(v *Value) bool {
 			break
 		}
 		sym := v_0_0_1.Aux
-		if !(isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil() && v.Pos.Line() > 1, v, "removed nil check")) {
+		if !(isSameSym(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
 			break
 		}
 		v.reset(OpInvalid)