[PATCH] D84345: [AMDGPU] Set the default globals address space to 1

[Dylan McKay via Phabricator via cfe-commits]

dylanmckay added inline comments.


================
Comment at: llvm/lib/IR/AutoUpgrade.cpp:4297
+  // address space of 1.
+  if (T.isAMDGPU() && !DL.contains("-G") && !DL.startswith("G")) {
+    return DL.empty() ? std::string("G1") : (DL + "-G1").str();
----------------
dylanmckay wrote:
> arichardson wrote:
> > akhuang wrote:
> > > arichardson wrote:
> > > > arsenm wrote:
> > > > > I would expect datalayout upgrades to work by parsing the old string, and checking the field values inside. I guess directly checking the string isn't a new problem here
> > > > I agree that would be less error prone. I wonder if there are cases where the old string may fail to parse so you have to do the textual upgrade first. I'm happy to make this change.
> > > > 
> > > > @akhuang is there a reason you used string parsing in D67631? Any objections to changing the code to parse the datalayout and add missing attributes?
> > > I don't think so; parsing the datalayout sounds better to me too. 
> > I just looked into parsing the DataLayout instead. Unfortunately the resulting code is more complicated since there are no setters in DataLayout and no way to create a normalized representation.
> > There's also no way to differentiate between no `-G ` passed and `-G0` so  something like `e-p:64:64-G0` will be converted to `e-p:64:64-G0-G1`
> > 
> I suspect it would be possible to use the existing `DataLayout(StringRef)` constructor on the string, then call `getDefaultGlobalsAddressSpace()` on it, explicitly ignoring modifying the datalayout for the special case of an explicit `-G0`.
> 
> For example,
> 
> ```cpp
>   DataLayout ParsedDL = DataLayout(DL);
>   if (T.isAMDGPU() && !DL.contains("-G0") &&ParsedDL.getDefaultGlobalsAddressSpace() != 1) {
>     return DL.empty() ? std::string("G1") : (DL + "-G1").str();
>   }
> ```
> 
> As I understand it, this would cover the fact that we cannot distinguish between an explicit default globals space of zero, and a datalayout without a default globals space (also `DL::getDefaultGlobalsAddressSpace() == 0`) by explicitly excluding the special case `-G0`
To be completely correct it should not assume that the global address space is not at the very start of the data layout as my initial snippet did. I've removed the `-` prefix from the `contains` check

```
  DataLayout ParsedDL = DataLayout(DL);
  if (T.isAMDGPU() && !DL.contains("G0") &&ParsedDL.getDefaultGlobalsAddressSpace() != 1) {
    return DL.empty() ? std::string("G1") : (DL + "-G1").str();
  }
```


Repository:
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  https://reviews.llvm.org/D84345/new/

https://reviews.llvm.org/D84345