[ia32,x64] Make more use of the 'leave' instruction

It is a little shorter and cheaper[1] than the equivalent
"mov sp,bp; pop bp".

Also remove support for the 'enter' instruction, since
- it is unused,
- it is neither shorter nor cheaper than the corresponding
  push and mov (in fact more expensive[1]), and
- our disassembler doesn't support it.

[1] See https://www.agner.org/optimize/instruction_tables.pdf

Change-Id: I6c99c2f3e53081aea55445a54e18eaf45baa79c2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2482822
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70660}

src/codegen/ia32/assembler-ia32.cc

@@ -510,13 +510,6 @@ void Assembler::pop(Operand dst) {
   emit_operand(eax, dst);
 }
 
-void Assembler::enter(const Immediate& size) {
-  EnsureSpace ensure_space(this);
-  EMIT(0xC8);
-  emit_w(size);
-  EMIT(0);
-}
-
 void Assembler::leave() {
   EnsureSpace ensure_space(this);
   EMIT(0xC9);

src/codegen/ia32/assembler-ia32.h

@@ -474,7 +474,6 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   void pop(Register dst);
   void pop(Operand dst);
 
-  void enter(const Immediate& size);
   void leave();
 
   // Moves

src/codegen/ia32/macro-assembler-ia32.cc

@@ -975,9 +975,7 @@ void MacroAssembler::LeaveExitFrameEpilogue() {
 }
 
 void MacroAssembler::LeaveApiExitFrame() {
-  mov(esp, ebp);
-  pop(ebp);
-
+  leave();
   LeaveExitFrameEpilogue();
 }
 

src/codegen/x64/assembler-x64.cc

@@ -1207,13 +1207,6 @@ void Assembler::decb(Operand dst) {
   emit_operand(1, dst);
 }
 
-void Assembler::enter(Immediate size) {
-  EnsureSpace ensure_space(this);
-  emit(0xC8);
-  emitw(size.value_);  // 16 bit operand, always.
-  emit(0);
-}
-
 void Assembler::hlt() {
   EnsureSpace ensure_space(this);
   emit(0xF4);

src/codegen/x64/assembler-x64.h

@@ -561,7 +561,6 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   void popq(Register dst);
   void popq(Operand dst);
 
-  void enter(Immediate size);
   void leave();
 
   // Moves

src/codegen/x64/macro-assembler-x64.cc

@@ -2488,8 +2488,7 @@ void TurboAssembler::LeaveFrame(StackFrame::Type type) {
          Immediate(StackFrame::TypeToMarker(type)));
     Check(equal, AbortReason::kStackFrameTypesMustMatch);
   }
-  movq(rsp, rbp);
-  popq(rbp);
+  leave();
 }
 
 #ifdef V8_TARGET_OS_WIN
@@ -2641,9 +2640,7 @@ void MacroAssembler::LeaveExitFrame(bool save_doubles, bool pop_arguments) {
 }
 
 void MacroAssembler::LeaveApiExitFrame() {
-  movq(rsp, rbp);
-  popq(rbp);
-
+  leave();
   LeaveExitFrameEpilogue();
 }
 

src/compiler/backend/ia32/code-generator-ia32.cc

@@ -509,10 +509,7 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
     }                                                  \
   } while (false)
 
-void CodeGenerator::AssembleDeconstructFrame() {
-  __ mov(esp, ebp);
-  __ pop(ebp);
-}
+void CodeGenerator::AssembleDeconstructFrame() { __ leave(); }
 
 void CodeGenerator::AssemblePrepareTailCall() {
   if (frame_access_state()->has_frame()) {

src/compiler/backend/x64/code-generator-x64.cc

@@ -681,8 +681,7 @@ void EmitWordLoadPoisoningIfNeeded(CodeGenerator* codegen,
 
 void CodeGenerator::AssembleDeconstructFrame() {
   unwinding_info_writer_.MarkFrameDeconstructed(__ pc_offset());
-  __ movq(rsp, rbp);
-  __ popq(rbp);
+  __ leave();
 }
 
 void CodeGenerator::AssemblePrepareTailCall() {