rnk added inline comments.
================
Comment at: clang/lib/CodeGen/TargetInfo.cpp:1858-1859
}
- return getIndirectResult(Ty, /*ByVal=*/false, State);
+ bool ByVal = IsVectorCall && Ty->isFloatingType();
+ return getIndirectResult(Ty, ByVal, State);
}
----------------
pengfei wrote:
> rnk wrote:
> > I would try to refactor this so that the vectorcall HFA that can't be
> > passed in SSE regs falls through to the following logic. I suspect that it
> > correctly handles each case that we care about:
> > - double: direct
> > - vector: indirect for alignment
> > - aggregate: indirect for alignment, any HFA will presumably be aligned to
> > more than 32bits
> >
> Not sure if I understand it correctly, the HFA is not a floating type, so it
> won't be affected. Add a test case for it.
> MSVC passes it indirectly too. https://gcc.godbolt.org/z/3qf4dTYfv
Thanks, I see what you mean. I thought the code for handling overaligned
aggregates would trigger, passing any HFA indirectly, but it does not for plain
FP HFAs. You can observe the difference by replacing `double` in HFA2 with
`__int64`, and see that HFA2 is passed underaligned on the stack:
https://gcc.godbolt.org/z/jqx4xcnjq
I still think this code would benefit from separating the regcall and
vectorcall cases, something like:
bool IsInReg = State.FreeSSERegs >= NumElts;
if (IsInReg)
State.FreeSSERegs -= NumElts;
if (IsRegCall) {
// handle regcall
if (IsInReg)
...
} else {
// handle vectorcall
if (IsInReg)
...
}
They seem to have pretty different rules both when SSE regs are available and
when not.
================
Comment at: clang/test/CodeGen/vectorcall.c:157
+// X86-SAME: <4 x float> inreg noundef %xmm5,
+// X86-SAME: double* noundef byval(double) align 4 %0)
#endif
----------------
pengfei wrote:
> rnk wrote:
> > Why not pass the double directly? That should be ABI compatible:
> > https://gcc.godbolt.org/z/W4rjn63b5
> Sorry, I'm not sure what's your mean here. Do you mean I should use your
> example as the test case? Here the case mocked `vectorcall_indirect_vec`,
> which I think is intended to check if the type, `inreg` and `byval` etc. are
> generated correctly.
I mean that these two LLVM prototypes are ABI compatible at the binary level
for i686, but the second is much easier to optimize:
double @byval(double* byval(double) %p) {
%v = load double, double* %p
ret double %v
}
double @direct(double %v) {
ret double %v
}
https://gcc.godbolt.org/z/MjEvdEKbT
Clang should generate the prototype.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D134797/new/
https://reviews.llvm.org/D134797
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
