[PATCH] D82615: [HWASan] [GlobalISel] Add +tagged-globals backend feature for GlobalISel

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp:693
+  if (OpFlags & AArch64II::MO_TAGGED) {
+    auto Tag = MI.getOperand(1);
+    Tag.setTargetFlags(AArch64II::MO_PREL | AArch64II::MO_G3);
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hctim wrote:
> arsenm wrote:
> > Isn't this a copy of the original operand, so the further modifications don't do anything? Needs a reference?
> I'm admittedly not very familiar with the backend, the goal here is to emit a *new* `movk` instruction w/ an immediate that's relocated with `R_AARCH64_MOVW_PREL_G3`.
> 
> I assume that we want to copy the operand so that we can generate the right relocation here?
You're copying the operand, and then you don't do anything with it after modifying it; you don't add Tag to the new instruction. In any case, having a freestanding MachineOperand value is a bad idea.

You're also creating a new generic virtual register for the selected instruction, so it needs a register class. You should create one with the final register class (I'm guessing AArch64::GPR64RegClass), and then set the type with MRI.setType (the above code does the same thing in the opposite order, by creating the vreg with a type and setting the class later)


Repository:
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  https://reviews.llvm.org/D82615/new/

https://reviews.llvm.org/D82615