[PATCH] D69987: [RISCV] Assemble/Disassemble v-ext instructions.

[Ferran Pallarès Roca via Phabricator via llvm-commits]

fpallares added a comment.

Hi Kai, I've added an inline comment regarding constraint validation:



================
Comment at: llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp:2283
+      unsigned Src2Reg = Inst.getOperand(1).getReg();
+      if (DestReg == Src2Reg)
+        return Error(Loc, "The destination vector register group cannot overlap"
----------------
In this function we are validating the overlap constraints by checking whether `DestReg` matches a vector operand. However, for widenings and narrowings those checks should be extended to validate that the operand doesn't belong to the same register group.

For instance:

`vwadd.vv v4, v4, v7`: The current code would give an error for this instruction.
`vwadd.vv v4, v5, v7`: There would be no error for this, even though `v5` will always overlap with any widened group of `v4`.
`vwadd.vv v4, v6, v7`: This should not emit any diagnostic because we can't really tell at this point if there will be an overlap.

Perhaps we are already checking this somewhere else and I missed it?

(Note that this will probably change with fractional LMUL in 0.9)



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  https://reviews.llvm.org/D69987/new/

https://reviews.llvm.org/D69987