[dev.typeparams] cmd/compile: simplify interface conversions

Simplify the implementation of interface conversions in the compiler.
Don't pass fields that aren't needed (the data word, usually) to the runtime.

For generics, we need to put a dynamic type in an interface. The new
dataWord function is exactly what we need (the type word will come
from a dictionary).

Change-Id: Iade5de5c174854b65ad248f35c7893c603f7be3d
Reviewed-on: https://go-review.googlesource.com/c/go/+/340029
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

4 files changed, 8 insertions, 9 deletions

diff --git a/test/devirt.go b/test/devirt.go
index e0149d8229..d5c815222e 100644
--- a/test/devirt.go
+++ b/test/devirt.go
@@ -31,9 +31,8 @@ func main() {
 		panic("not 3")
 	}
 
-	// Can't do types that aren't "direct" interfaces (yet).
 	r = indirectiface{3, 4, 5}
-	if r.Value() != 12 {
+	if r.Value() != 12 { // ERROR "de-virtualizing call$"
 		panic("not 12")
 	}
 }
diff --git a/test/fixedbugs/issue20250.go b/test/fixedbugs/issue20250.go
index 1a513bea56..aed7b25d1b 100644
--- a/test/fixedbugs/issue20250.go
+++ b/test/fixedbugs/issue20250.go
@@ -17,7 +17,7 @@ type T struct {
 func f(a T) { // ERROR "live at entry to f: a"
 	var e interface{} // ERROR "stack object e interface \{\}$"
 	func() {          // ERROR "live at entry to f.func1: a &e"
-		e = a.s // ERROR "live at call to convT2E: &e" "stack object a T$"
+		e = a.s // ERROR "live at call to convT: &e" "stack object a T$"
 	}()
 	// Before the fix, both a and e were live at the previous line.
 	_ = e
diff --git a/test/live.go b/test/live.go
index 856e56f3d2..6130f7f069 100644
--- a/test/live.go
+++ b/test/live.go
@@ -144,8 +144,8 @@ var i9 interface{}
 func f9() bool {
 	g8()
 	x := i9
-	y := interface{}(g18()) // ERROR "live at call to convT2E: x.data$" "live at call to g18: x.data$" "stack object .autotmp_[0-9]+ \[2\]string$"
-	i9 = y                  // make y escape so the line above has to call convT2E
+	y := interface{}(g18()) // ERROR "live at call to convT: x.data$" "live at call to g18: x.data$" "stack object .autotmp_[0-9]+ \[2\]string$"
+	i9 = y                  // make y escape so the line above has to call convT
 	return x != y
 }
 
@@ -503,7 +503,7 @@ func f31(b1, b2, b3 bool) {
 		g31(g18()) // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
 	if b2 {
-		h31(g18()) // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
+		h31(g18()) // ERROR "live at call to convT: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
 	}
 	if b3 {
 		panic(g18())
diff --git a/test/live_regabi.go b/test/live_regabi.go
index d362ee287d..2883b83bae 100644
--- a/test/live_regabi.go
+++ b/test/live_regabi.go
@@ -139,8 +139,8 @@ var i9 interface{}
 func f9() bool {
 	g8()
 	x := i9
-	y := interface{}(g18()) // ERROR "live at call to convT2E: x.data$" "live at call to g18: x.data$" "stack object .autotmp_[0-9]+ \[2\]string$"
-	i9 = y                  // make y escape so the line above has to call convT2E
+	y := interface{}(g18()) // ERROR "live at call to convT: x.data$" "live at call to g18: x.data$" "stack object .autotmp_[0-9]+ \[2\]string$"
+	i9 = y                  // make y escape so the line above has to call convT
 	return x != y
 }
 
@@ -498,7 +498,7 @@ func f31(b1, b2, b3 bool) {
 		g31(g18()) // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
 	if b2 {
-		h31(g18()) // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
+		h31(g18()) // ERROR "live at call to convT: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
 	}
 	if b3 {
 		panic(g18())