cmd: remove GOEXPERIMENT=nounified knob

This CL removes the GOEXPERIMENT=nounified knob, and any conditional
statements that depend on that knob. Further CLs to remove unreachable
code follow this one.

Updates #57410.

Change-Id: I39c147e1a83601c73f8316a001705778fee64a91
Reviewed-on: https://go-review.googlesource.com/c/go/+/458615
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

1 files changed, 42 insertions, 48 deletions

diff --git a/src/cmd/compile/internal/devirtualize/devirtualize.go b/src/cmd/compile/internal/devirtualize/devirtualize.go
index 554e935c3e..6c41d4efd8 100644
--- a/src/cmd/compile/internal/devirtualize/devirtualize.go
+++ b/src/cmd/compile/internal/devirtualize/devirtualize.go
@@ -57,58 +57,52 @@ func Call(call *ir.CallExpr) {
 		return
 	}
 
-	if base.Debug.Unified != 0 {
-		// N.B., stencil.go converts shape-typed values to interface type
-		// using OEFACE instead of OCONVIFACE, so devirtualization fails
-		// above instead. That's why this code is specific to unified IR.
-
-		// If typ is a shape type, then it was a type argument originally
-		// and we'd need an indirect call through the dictionary anyway.
-		// We're unable to devirtualize this call.
-		if typ.IsShape() {
-			return
-		}
+	// If typ is a shape type, then it was a type argument originally
+	// and we'd need an indirect call through the dictionary anyway.
+	// We're unable to devirtualize this call.
+	if typ.IsShape() {
+		return
+	}
 
-		// If typ *has* a shape type, then it's an shaped, instantiated
-		// type like T[go.shape.int], and its methods (may) have an extra
-		// dictionary parameter. We could devirtualize this call if we
-		// could derive an appropriate dictionary argument.
-		//
-		// TODO(mdempsky): If typ has has a promoted non-generic method,
-		// then that method won't require a dictionary argument. We could
-		// still devirtualize those calls.
-		//
-		// TODO(mdempsky): We have the *runtime.itab in recv.TypeWord. It
-		// should be possible to compute the represented type's runtime
-		// dictionary from this (e.g., by adding a pointer from T[int]'s
-		// *runtime._type to .dict.T[int]; or by recognizing static
-		// references to go:itab.T[int],iface and constructing a direct
-		// reference to .dict.T[int]).
-		if typ.HasShape() {
-			if base.Flag.LowerM != 0 {
-				base.WarnfAt(call.Pos(), "cannot devirtualize %v: shaped receiver %v", call, typ)
-			}
-			return
+	// If typ *has* a shape type, then it's an shaped, instantiated
+	// type like T[go.shape.int], and its methods (may) have an extra
+	// dictionary parameter. We could devirtualize this call if we
+	// could derive an appropriate dictionary argument.
+	//
+	// TODO(mdempsky): If typ has has a promoted non-generic method,
+	// then that method won't require a dictionary argument. We could
+	// still devirtualize those calls.
+	//
+	// TODO(mdempsky): We have the *runtime.itab in recv.TypeWord. It
+	// should be possible to compute the represented type's runtime
+	// dictionary from this (e.g., by adding a pointer from T[int]'s
+	// *runtime._type to .dict.T[int]; or by recognizing static
+	// references to go:itab.T[int],iface and constructing a direct
+	// reference to .dict.T[int]).
+	if typ.HasShape() {
+		if base.Flag.LowerM != 0 {
+			base.WarnfAt(call.Pos(), "cannot devirtualize %v: shaped receiver %v", call, typ)
 		}
+		return
+	}
 
-		// Further, if sel.X's type has a shape type, then it's a shaped
-		// interface type. In this case, the (non-dynamic) TypeAssertExpr
-		// we construct below would attempt to create an itab
-		// corresponding to this shaped interface type; but the actual
-		// itab pointer in the interface value will correspond to the
-		// original (non-shaped) interface type instead. These are
-		// functionally equivalent, but they have distinct pointer
-		// identities, which leads to the type assertion failing.
-		//
-		// TODO(mdempsky): We know the type assertion here is safe, so we
-		// could instead set a flag so that walk skips the itab check. For
-		// now, punting is easy and safe.
-		if sel.X.Type().HasShape() {
-			if base.Flag.LowerM != 0 {
-				base.WarnfAt(call.Pos(), "cannot devirtualize %v: shaped interface %v", call, sel.X.Type())
-			}
-			return
+	// Further, if sel.X's type has a shape type, then it's a shaped
+	// interface type. In this case, the (non-dynamic) TypeAssertExpr
+	// we construct below would attempt to create an itab
+	// corresponding to this shaped interface type; but the actual
+	// itab pointer in the interface value will correspond to the
+	// original (non-shaped) interface type instead. These are
+	// functionally equivalent, but they have distinct pointer
+	// identities, which leads to the type assertion failing.
+	//
+	// TODO(mdempsky): We know the type assertion here is safe, so we
+	// could instead set a flag so that walk skips the itab check. For
+	// now, punting is easy and safe.
+	if sel.X.Type().HasShape() {
+		if base.Flag.LowerM != 0 {
+			base.WarnfAt(call.Pos(), "cannot devirtualize %v: shaped interface %v", call, sel.X.Type())
 		}
+		return
 	}
 
 	dt := ir.NewTypeAssertExpr(sel.Pos(), sel.X, nil)