| Commit message (Expand) | Author | Files | Lines |
|---|
| 2018-10-18 | adjust types in FILE struct to make line buffering check less expensive•••the choice of signed char for lbf was a theoretically space-saving
hack that was not helping, and was unwantedly expensive. while
comparing bytes against a byte-sized member sounds easy, the trick
here was that the byte to be compared was unsigned while the lbf
member was signed, making it possible to set lbf negative to disable
line buffering. however, this imposed a requirement to promote both
operands, zero-extending one and sign-extending the other, in order to
compare them.
to fix this, repurpose the waiters count slot (unused since commit
c21f750727515602a9e84f2a190ee8a0a2aeb2a1). while we're at it, switch
mode (orientation) from signed char to int as well. this makes no
semantic difference (its only possible values are -1, 0, and 1) but it
might help on archs where byte access is awkward.
| Rich Felker | 1 | -4/+2 |
| 2018-10-18 | optimize internal putc_unlocked macro used in putc•••to check whether flush due to line buffering is needed, the int-type
character argument must be truncated to unsigned char for comparison.
if the original value is subsequently passed to __overflow, it must be
preserved, adding to register pressure. since it doesn't matter,
truncate all uses so the original value is no longer live.
| Rich Felker | 1 | -1/+2 |
| 2018-10-18 | fix wrong result for putc variants due to operator precedence•••the internal putc_unlocked macro was wrongly returning a meaningless
boolean result rather than the written character or EOF.
bug was found by reading (very surprising) asm.
| Rich Felker | 1 | -1/+1 |
| 2018-10-18 | further optimize getc/putc when locking is needed•••check whether the lock is free before loading the calling thread's
tid. if so, just use a dummy tid value that cannot compare equal to
any actual thread id (because it's one bit wider). this also avoids
the need to save the tid and pass it to locking_getc or locking_putc,
reducing register pressure.
this change might slightly hurt the case where the caller already
holds the lock, but it does not affect the single-threaded case, and
may significantly improve the multi-threaded case, especially on archs
where loading the thread pointer is disproportionately expensive like
early mips and arm ISA levels. but even on i386 it helps, at least on
some machines; I measured roughly a 10-15% improvement.
| Rich Felker | 2 | -10/+10 |
| 2018-10-18 | use prototype for function pointer in static link libc init barrier•••this is not needed for correctness, but doesn't hurt, and in some
cases the compiler may pessimize the call assuming the callee might be
variadic when it lacks a prototype.
| Rich Felker | 1 | -1/+1 |
| 2018-10-18 | fix error in constraints for static link libc init barrier•••commit 4390383b32250a941ec616e8bff6f568a801b1c0 inadvertently used "r"
instead of "0" for the input constraint, which only happened to work
for the configuration I tested it on because it usually makes sense
for the compiler to choose the same input and output register.
| Rich Felker | 1 | -1/+1 |
