x32: Fix, optimize and cleanup RSEQ_* accessors

Add missing "memory" clobber to accessors.  The "memory" clobber
tells the compiler that the assembly code performs memory reads
or writes to items other than those listed in the input and output
operands (for example, accessing the memory pointed to by one of
the input parameters).

Use MOVZBL instead of MOVB when reading 1-byte memory location
into a register.  MOVB to a register actually inserts into the LSB
of the word-sized register, making the result dependent on
the previous register value.  MOVZBL avoids this issue.

Change %P asm operand modifiers to %c.  The ‘c’ modifier is a
generic asm operand modifier that requires a constant operand and
prints the constant expression without punctuation.

Replace %b asm operand modifiers with explicit casts.  Explicit
casts inform the compiler which part of the register value is used,
allowing it to perform additional optimizations (e.g. narrowing the
preceding operation).

Remove %q asm operand modifiers.  Since the value is already cast
to 'long long int', the compiler will emit a 64-bit register name
in the assembly without needing %q.

No functional changes intended.

Tested-by: H.J. Lu <hjl.tools@gmail.com>
Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

0 files changed, 0 insertions, 0 deletions