[PATCH] D110466: [llvm-profgen][CSSPGO] On-demand function size computation for preinliner

[Lei Wang via Phabricator via llvm-commits]

wlei added inline comments.


================
Comment at: llvm/tools/llvm-profgen/ProfiledBinary.cpp:550-551
+                                                       uint64_t EndOffset) {
+  uint32_t Index = getIndexForOffset(StartOffset);
+  if (CodeAddrs[Index] != StartOffset)
+    WithColor::warning() << "Invalid start instruction at "
----------------
wenlei wrote:
> wlei wrote:
> > wenlei wrote:
> > > Is this the same as `addressIsCode`? or perhaps we need `addrOffsetIsCode`?
> > The input of `addressIsCode` is the `address`. I guess the confusing part is `CodeAddrs` so I changed to `codeAddrOffsets`.
> What I meant is we could have something like this:
> ```
>   bool addrOffsetIsCode(uint64_t Offset) const {
>     return Offset2LocStackMap.find(Offset) != Offset2LocStackMap.end();
>   }
> ```
> 
>   which is similar to addressIsCode, except that we use offset now.
> 
> 
> ```
>   bool addressIsCode(uint64_t Address) const {
>     uint64_t Offset = virtualAddrToOffset(Address);
>     return Offset2LocStackMap.find(Offset) != Offset2LocStackMap.end();
>   }
> ```
> 
> I think it's cleaner to use API instead of dealing with internals like `codeAddrOffsets` directly when possible. Also `Offset2LocStackMap` is unordered_map while `codeAddrOffsets ` is sorted vector. So look up with `Offset2LocStackMap` is faster.
I see. Here I used `uint32_t Index = getIndexForOffset(StartOffset);` because I need to use the `Index` to iterate  all the invalid instructions  which are stored in `codeAddrOffsets`. `Offset2LocStackMap ` doesn't give the `Index`.
```
Index =  getIndexForOffset(StartOffset);
while(codeAddrOffsets[Index] <= End) {
    // use codeAddrOffsets[Index]  to do something.
    Index++;
}
```
To avoid using `codeAddrOffsets` directly, previously we use `IP`, but IP only working on `Address` and this introduces many redundancy. i. e.  we need to change `offset` --> `address` and then change `address` back --> `offset`.



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https://reviews.llvm.org/D110466