[PATCH] D116464: [SPIRV 5/6] Add LegalizerInfo, InstructionSelector and utilities

[Aleksandr Bezzubikov via Phabricator via llvm-commits]

zuban32 added inline comments.


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Comment at: llvm/lib/Target/SPIRV/SPIRVLegalizerInfo.cpp:361-365
+  MachineInstr &AssignTypeInst =
+      *(MRI.use_instr_begin(MI.getOperand(0).getReg()));
+  auto NewReg = createNewIdReg(MI.getOperand(0).getReg(), Opc, MRI, *GR).first;
+  AssignTypeInst.getOperand(1).setReg(NewReg);
+  MI.getOperand(0).setReg(NewReg);
----------------
arsenm wrote:
> zuban32 wrote:
> > arsenm wrote:
> > > You're assuming there's only a single use, and your legalize action should only touch the passed instruction
> > The single-use constraint is enforced by the design of our target, every non-void instruction have the only user - type assignment instruction, which in turn may have multiple users just as the original instruction before.
> This is not a property the target can decide, the incoming IR can have multiple uses. It's simply wrong to rely on it like this
Why not if we have a target-specific LLVM IR pass making that assumption always true?


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D116464/new/

https://reviews.llvm.org/D116464