Add comments to undocumented functions and fix other comments

Grouping a couple of small, non-functional fixes:

- add a comment to GetStackParameterDelta
- small typo fixes to a couple of places I saw while reading related
code

Bug: v8:11879
Change-Id: I8566c9778fd6268b08ea3aefbdaa84ef894bcd35
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2997922Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75490}

src/builtins/arm64/builtins-arm64.cc

@@ -3079,7 +3079,7 @@ void Builtins::Generate_CEntry(MacroAssembler* masm, int result_size,
   // The stack on entry holds the arguments and the receiver, with the receiver
   // at the highest address:
   //
-  //    sp]argc-1]: receiver
+  //    sp[argc-1]: receiver
   //    sp[argc-2]: arg[argc-2]
   //    ...           ...
   //    sp[1]:      arg[1]

src/compiler/linkage.h

@@ -395,6 +395,8 @@ class V8_EXPORT_PRIVATE CallDescriptor final
 
   const char* debug_name() const { return debug_name_; }
 
+  // Difference between the number of parameter slots of *this* and
+  // *tail_caller* (callee minus caller).
   int GetStackParameterDelta(const CallDescriptor* tail_caller) const;
 
   // Returns the offset to the area below the parameter slots on the stack,

test/unittests/compiler/linkage-tail-call-unittest.cc

@@ -205,7 +205,7 @@ TEST_F(LinkageTailCall, MatchingStackParameters) {
   LocationSignature locations1(1, 3, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 3, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations1);
 
@@ -231,7 +231,7 @@ TEST_F(LinkageTailCall, NonMatchingStackParameters) {
   LocationSignature locations1(1, 3, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 3, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations1);
 
@@ -258,7 +258,7 @@ TEST_F(LinkageTailCall, MatchingStackParametersExtraCallerRegisters) {
   LocationSignature locations1(1, 5, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 3, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations1);
 
@@ -285,7 +285,7 @@ TEST_F(LinkageTailCall, MatchingStackParametersExtraCalleeRegisters) {
   LocationSignature locations1(1, 3, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 5, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations1);
 
@@ -313,7 +313,7 @@ TEST_F(LinkageTailCall, MatchingStackParametersExtraCallerRegistersAndStack) {
   LocationSignature locations1(1, 5, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 3, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations2);
 
@@ -343,7 +343,7 @@ TEST_F(LinkageTailCall, MatchingStackParametersExtraCalleeRegistersAndStack) {
   LocationSignature locations1(1, 3, location_array);
   CallDescriptor* desc1 = NewStandardCallDescriptor(&locations1);
 
-  // Caller
+  // Callee
   LocationSignature locations2(1, 5, location_array);
   CallDescriptor* desc2 = NewStandardCallDescriptor(&locations2);