[PATCH] D66459: Make ShrinkWrap more consistent.
zuojian lin via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 20 18:11:13 PDT 2019
linzj marked 2 inline comments as done.
linzj added inline comments.
================
Comment at: llvm/lib/CodeGen/ShrinkWrap.cpp:275
}
+ if (MI.isTerminator())
+ return false;
----------------
chill wrote:
> I don't believe this is correct. A terminator instruction can well use and/or def a CSR, e.g. an indirect branch, a table jump, a hw loop instruction, ...
>
>
Oh, that's a mistake. How about MI.isReturn()? I just want to handle sibling calls.
They are essentially the same as returns.
================
Comment at: llvm/lib/CodeGen/ShrinkWrap.cpp:293
+ UseOrDefCSR =
+ (!MI.isCall() && PhysReg == SP) || getCurrentCSRs(RS).count(PhysReg);
} else if (MO.isRegMask()) {
----------------
chill wrote:
> Why is that needed? The set of //actual// CSRs ought to be always a subset of the set of //possible// CSRs.
>
I am actually making LLVM a code generator for V8 turbofan. V8 needs to save a specific set of registers at the entry of a function depending on the type of this function. For example, a JS function needs to save r0, r1,r7 along with fp, lr. And a wasm function needs to spill r3 at sp - 16.
At this context, I need to add additional CSRs at frame lowering's assignCalleeSavedSpillSlots. So getCurrentCSRs maybe a super set of the set of possible CSRs.
Repository:
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https://reviews.llvm.org/D66459/new/
https://reviews.llvm.org/D66459
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