cmd/compile: eliminate NoFramePointer

The NoFramePointer function flag is no longer used, so this CL
eliminates it. This cleans up some confusion between the compiler's
NoFramePointer flag and obj's NOFRAME flag. NoFramePointer was
intended to eliminate the saved base pointer on x86, but it was
translated into obj's NOFRAME flag. On x86, NOFRAME does mean to omit
the saved base pointer, but on ppc64 and s390x it has a more general
meaning of omitting *everything* from the frame, including the saved
LR and ppc64's "fixed frame". Hence, on ppc64 and s390x there are far
fewer situations where it is safe to set this flag.

Change-Id: If68991310b4d00638128c296bdd57f4ed731b46d
Reviewed-on: https://go-review.googlesource.com/92036
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/gc/gsubr.go

@@ -188,9 +188,6 @@ func (f *Func) initLSym() {
 	if f.Wrapper() {
 		flag |= obj.WRAPPER
 	}
-	if f.NoFramePointer() {
-		flag |= obj.NOFRAME
-	}
 	if f.Needctxt() {
 		flag |= obj.NEEDCTXT
 	}

src/cmd/compile/internal/gc/syntax.go

@@ -464,7 +464,6 @@ const (
 	funcNeedctxt                  // function uses context register (has closure variables)
 	funcReflectMethod             // function calls reflect.Type.Method or MethodByName
 	funcIsHiddenClosure
-	funcNoFramePointer      // Must not use a frame pointer for this function
 	funcHasDefer            // contains a defer statement
 	funcNilCheckDisabled    // disable nil checks when compiling this function
 	funcInlinabilityChecked // inliner has already determined whether the function is inlinable
@@ -476,7 +475,6 @@ func (f *Func) Wrapper() bool             { return f.flags&funcWrapper != 0 }
 func (f *Func) Needctxt() bool            { return f.flags&funcNeedctxt != 0 }
 func (f *Func) ReflectMethod() bool       { return f.flags&funcReflectMethod != 0 }
 func (f *Func) IsHiddenClosure() bool     { return f.flags&funcIsHiddenClosure != 0 }
-func (f *Func) NoFramePointer() bool      { return f.flags&funcNoFramePointer != 0 }
 func (f *Func) HasDefer() bool            { return f.flags&funcHasDefer != 0 }
 func (f *Func) NilCheckDisabled() bool    { return f.flags&funcNilCheckDisabled != 0 }
 func (f *Func) InlinabilityChecked() bool { return f.flags&funcInlinabilityChecked != 0 }
@@ -487,7 +485,6 @@ func (f *Func) SetWrapper(b bool)             { f.flags.set(funcWrapper, b) }
 func (f *Func) SetNeedctxt(b bool)            { f.flags.set(funcNeedctxt, b) }
 func (f *Func) SetReflectMethod(b bool)       { f.flags.set(funcReflectMethod, b) }
 func (f *Func) SetIsHiddenClosure(b bool)     { f.flags.set(funcIsHiddenClosure, b) }
-func (f *Func) SetNoFramePointer(b bool)      { f.flags.set(funcNoFramePointer, b) }
 func (f *Func) SetHasDefer(b bool)            { f.flags.set(funcHasDefer, b) }
 func (f *Func) SetNilCheckDisabled(b bool)    { f.flags.set(funcNilCheckDisabled, b) }
 func (f *Func) SetInlinabilityChecked(b bool) { f.flags.set(funcInlinabilityChecked, b) }