arichardson 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:
> 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();
> }
> ```
We then end up overwriting explicitly specified `G<N>` flags. Maybe some tests
would like to check that overriding the globals address space works? Also I
believe this can result in an invalid datalayout: `"...-G2"` will be converted
to `"...-G2-G1"`.
Not sure what the correct approach is @arsenm ?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D84345/new/
https://reviews.llvm.org/D84345
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