asb added inline comments.
================
Comment at: lib/CodeGen/TargetInfo.cpp:8858
+ else
+ NeededArgGPRs = 1;
+
----------------
efriedma wrote:
> It looks like the ABI says there's a special rule for varargs here?
You're right, I neglected vararg calls. Now addressed and test cases added. The
difference is only observable on RV64 I believe (as we only use the GPR
tracking to decide whether an argument should be extended or not, and the
argument promotion rules mean you'll never see signext/zeroext on varargs in
RV32).
================
Comment at: lib/CodeGen/TargetInfo.cpp:8914
+Address RISCVABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
+ QualType Ty) const {
+ CharUnits SlotSize = CharUnits::fromQuantity(XLen / 8);
----------------
efriedma wrote:
> The type of va_list and the behavior of va_arg should be documented in the
> ABI doc... but apparently it's missing at the moment? (I mean, this is the
> obvious implementation from what is mentioned, but it would be nice to see
> something more explicit.)
I've started an attempt to better document things
https://github.com/riscv/riscv-elf-psabi-doc/pull/60
================
Comment at: test/CodeGen/riscv32-abi.c:118
+// single 2*xlen-sized argument, to ensure that alignment can be maintained if
+// it spills to the stack
+
----------------
efriedma wrote:
> Please clarify this comment; the ABI doc doesn't say anything about aligning
> arguments whose alignment is 2✕XLEN, except in the case of varargs.
I've corrected the comment to say "if passed on the stack" and submitted a PR
to clarify the ABI doc https://github.com/riscv/riscv-elf-psabi-doc/pull/59
https://reviews.llvm.org/D40023
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