rnk added inline comments.
================
Comment at: lib/CodeGen/TargetInfo.cpp:919
/// IsX86_MMXType - Return true if this is an MMX type.
bool IsX86_MMXType(llvm::Type *IRType) {
- // Return true if the type is an MMX type <2 x i32>, <4 x i16>, or <8 x i8>.
----------------
wxiao3 wrote:
> rnk wrote:
> > I think looking at the LLVM type to decide how something should be passed
> > is a bad pattern to follow. We should look at the clang AST to decide how
> > things will be passed, not LLVM types. Would that be complicated? Are there
> > aggregate types that end up getting passed directly in MMX registers?
> For x86 32 bit target, no aggregate types end up getting passed in MMX
> register.
> The only type passed by MMX is
>
> > __m64
>
> which is defined in header file (mmintrin.h):
>
>
> ```
> typedef long long __m64 __attribute__((__vector_size__(8), __aligned__(8)));
> ```
>
> Yes, it would be good if we define _m64 as a builtin type and handle it in
> AST level. But I'm afraid that it won't be a trivial work. Since GCC also
> handles __m64 in the same way as Clang currently does, can we just keep
> current implementation as it is?
>
That's not quite what I'm suggesting. I'm saying that IsX86_MMXType should take
a QualType parameter, and it should check if that qualtype looks like the __m64
vector type, instead of converting the QualType to llvm::Type and then checking
if the llvm::Type is a 64-bit vector. Does that seem reasonable? See the code
near the call site conditionalized on IsDarwinVectorABI which already has
similar logic.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59744/new/
https://reviews.llvm.org/D59744
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