Fangrui Song 8afd831b45 ms inline asm: recognize case-insensitive JMP and CALL as TargetLowering::C_Address ...

In a `__asm` block, a symbol reference is usually a memory constraint
(indirect TargetLowering::C_Memory) [LOOP]. CALL and JUMP instructions are special
that `__asm call k` can be an address constraint, if `k` is a function.

Clang always gives us indirect TargetLowering::C_Memory and need to convert it
to direct TargetLowering::C_Address. D133914 implements this conversion, but
does not consider JMP or case-insensitive CALL. This patch implements the missing
cases, so that `__asm jmp k` (`jmp ${0:P}`) will correctly lower to `jmp _k`
instead of `jmp dword ptr [_k]`.

(`__asm call k` lowered to `call dword ptr ${0:P}` and is fixed by D149695 to
lower to `call ${0:P}` instead.)

[LOOP]: Some instructions like LOOP{,E,NE} and Jcc always use an address
constraint (`loop _k` instead of `loop dword ptr [_k]`).

After this patch and D149579, all the following cases will be correct.
```
int k(int);
int (*kptr)(int);
...
__asm call k; // correct without this patch
__asm CALL k; // correct, but needs this patch to be compatible with D149579
__asm jmp k;  // correct, but needs this patch to be compatible with D149579
__asm call kptr; // will be fixed by D149579.  "Broken case" in clang/test/CodeGen/ms-inline-asm-functions.c
__asm jmp kptr;  // will be fixed by this patch and D149579
```

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D149920

2023-05-05 15:32:32 -07:00

2.1 KiB

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