On Tue, 16 Dec 2025, LIU Hao wrote:
This solves a leftover in 19fb46e9e8aaf10bf917266e96362fe2b4414934. Because
we
cannot pass a segmented memory reference to assembly, the (absolute) address
was
always passed in a register, preventing optimization when it could be
constant,
for example, in `NtCurrentTeb()`:
# -masm=att
movl $48, %eax
movq %gs:(%eax), %rax
# -masm=intel
mov eax, 48
mov rax, gs:[eax]
With this commit, a constant address is allowed to be passed as a constant to
inline assembly. There are two cases:
1. In AT&T syntax, there are different ways to say whether a constant is an
immediate or (part of) an address. For our use, we must write the operand
in its address form, using the `a` modifier: `mov %%gs:%a1, %0`
2. In Intel syntax, the `a` modifier on a constant would produce a `ds:`
segment prefix, so we must not use that. On the other hand, the address
form
of any kind of operands is actually unified, so we enclose the operand in
brackets, to indicate an address: `mov %0, gs:[%1]`
`NtCurrentTeb()` now produces:
# -masm=att
movq %gs:48, %rax
# -masm=intel
mov rax, gs:[48]
Signed-off-by: LIU Hao <[email protected]>
---
mingw-w64-headers/include/psdk_inc/intrin-impl.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
I'm not really familiar enough with x86 to follow the nuance differences
here, so I'll just trust you on it. I.e. if you've checked it properly
yourself and are confident about it, feel free to go ahead with it.
// Martin
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