[PATCH] D125916: [PowerPC] Defined and lowered llvm.ppc.kill.canary intrinsic

Paul Scoropan via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Mon Jun 27 08:08:15 PDT 2022

pscoro abandoned this revision.
pscoro added inline comments.

Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:11136
+    MachineFrameInfo &MFI = MF.getFrameInfo();
+    int SPI = MFI.getStackProtectorIndex(); // should return  -1
shchenz wrote:
> Why should return -1?
The source code for getStackProtectorIndex just returns StackProtectorIndex which is initialized to -1, it makes sense as the stack protector byte should be right before the stack frame begins

Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:11144
+    unsigned int deadBird = 0x4C6C566D; // replaces canary word
shchenz wrote:
> nit: the first letter should be upper for `deadBird` according to LLVM coding style.
> And how can we make sure `0x4C6C566D` is not the same with the canary word load with `TargetOpcode::LOAD_STACK_GUARD`?
What would you suggest for this? I'm not sure exactly how the canary word is created, is it worth loading the canary word first, manipulating it to make sure that we store something different?

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