[PATCH] D108871: [AArch64] Implement target hook function to decide folding (mul (add x, c1), c2)

[Ben Shi via Phabricator via llvm-commits]

benshi001 marked an inline comment as done.
benshi001 added inline comments.


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Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:12152
+// Return true if Imm can be composed by a single MOVZ instruction.
+static inline bool isMOVZImm(uint64_t Imm, unsigned Sz) {
+  assert((Sz == 64) || (Sz == 32) && "invalid immediate size");
----------------
dmgreen wrote:
> benshi001 wrote:
> > benshi001 wrote:
> > > dmgreen wrote:
> > > > Can this use AArch64TTIImpl::getIntImmCost in some way?
> > > I think it is hard. Since the  API
> > > 
> > > ```
> > > TargetTransformInfo
> > > AArch64TargetMachine::getTargetTransformInfo(const Function &F) {
> > >   return TargetTransformInfo(AArch64TTIImpl(this, F));
> > > }
> > > ```
> > > 
> > > requires a `Function` object, but the target hook has only two `SDValue` parameters.
> > > 
> > > So the cheapest way is implementing a new but short `isMOVZImm` helper function.
> > I have simplified it to one additional helper function.
> It's more about not repeating the same (or similar) code. Can this at least use AArch64_IMM::expandMOVImm and check the number of instructions?
Thanks for your suggestion. Using `AArch64_IMM::expandMOVImm` makes the check more clear and accurate !!!


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https://reviews.llvm.org/D108871