cmd/internal/gc: inline x := y.(*T) and x, ok := y.(*T)

These can be implemented with just a compare and a move instruction.
Do so, avoiding the overhead of a call into the runtime.

These assertions are a significant cost in Go code that uses interface{}
as a safe alternative to C's void* (or unsafe.Pointer), such as the
current version of the Go compiler.

*T here includes pointer to T but also any Go type represented as
a single pointer (chan, func, map). It does not include [1]*T or struct{*int}.
That requires more work in other parts of the compiler; there is a TODO.

Change-Id: I7ff681c20d2c3eb6ad11dd7b3a37b1f3dda23965
Reviewed-on: https://go-review.googlesource.com/7862
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 0 insertions, 19 deletions

diff --git a/src/runtime/error.go b/src/runtime/error.go
index d8af4f156d..4280306ac5 100644
--- a/src/runtime/error.go
+++ b/src/runtime/error.go
@@ -43,25 +43,6 @@ func (e *TypeAssertionError) Error() string {
 		": missing method " + e.missingMethod
 }
 
-// For calling from C.
-func newTypeAssertionError(ps1, ps2, ps3 *string, pmeth *string, ret *interface{}) {
-	var s1, s2, s3, meth string
-
-	if ps1 != nil {
-		s1 = *ps1
-	}
-	if ps2 != nil {
-		s2 = *ps2
-	}
-	if ps3 != nil {
-		s3 = *ps3
-	}
-	if pmeth != nil {
-		meth = *pmeth
-	}
-	*ret = &TypeAssertionError{s1, s2, s3, meth}
-}
-
 // An errorString represents a runtime error described by a single string.
 type errorString string