The guard flag was named .init-once.<global>, and . and - are ordinary
symbol constituents, so (defvar .init-once.x i64 7) beside a computed x
emitted the same symbol twice: the dev build died at the assembler on both
backends, and the flag's Bool was registered over the user's global in
Emit.globals so the store came out as an i1. It is .init~once.<global> now;
~ terminates a symbol in the reader, the same trick destructure~N uses.
test/programs/dev-rerun.flan carries such a global and no new printed line.
Three places said a defconst is the linker's image on one backend and a
constructor's stores on the other and a re-run reaches neither. Tast.const_init
splits on the initialiser and not on the form, so that holds only for a
constant initialiser; a computed defconst is guarded like a defvar on x86 and
refused outright by emit.ml's const. The sentences now say that, including
the divergence.
emit.ml also claimed Check.no_transfer_in_init made it impossible to leave the
guarded branch between the store and the flag. It is syntactic over the
written initialiser only: a callee can signal unhandled and take the call's
transfer edge out, leaving the flag false — which is what should happen, since
the next run retries. Read off the emitted IR for such a program.
The x86 float-Rem comment says why the dead movabs before fmod is kept, and
its mid-sentence line break is gone; math3.flan's first float-% line prints
six values, not four.
There is no SSE remainder instruction, and LLVM does not invent one: at -O0
it lowers frem to fmod or fmodf. The backend now calls those two symbols
rather than refusing the operator, which is agreement by construction rather
than a second hand-written identity that would have to get every rounding,
every signed zero and every infinity right on its own.
Rem was the only gap. emit.ml's float surface is Add, Sub, Mul, Div, Rem and
the six comparisons; x86 had everything but Rem, and its comparisons already
build LLVM's ordered predicates out of ucomis, setcc and setnp.
math3.flan grows the operator spelling beside the fmod-f32/fmod-f64 calls it
already had, through globals so the pair is not folded before either backend
sees an operator. FIX.org records the ruling the fix came from.
The prelude's declare surface was five f32 functions, and the five were there
because somebody needed each one. Everything else a caller wanted was written
as a declare at the top of their own file -- the identical libm call with none
of the caveats written down.
So the rest of libm is here: tan, the three inverses, the three logarithms,
exp, fmod, hypot, cbrt, fabs, and an f64 face for every one of them including
the five that already existed. A declare is a line, a symbol already on the
link, and nothing in either backend, which is why this was cheap enough to do
completely rather than one function at a time.
The f64 half is not decoration. f32 is what a position is; f64 is what a
measurement is -- the clock, parse-f64, format-f64, any sum over more than a
few thousand terms -- and having only the f32 face forced a cast down and back
at each of those boundaries, which is where the precision went.
The paragraph the sqrt note draws for itself is now drawn once for the family:
IEEE-754 specifies sqrt, fabs, floor, ceil, round and fmod as exact or
correctly rounded, so those agree bit for bit across glibc, musl and
wasi-libc; it requires nothing of the rest, so the sand-grid rule covers all
of them unchanged. floor, ceil and round are Flan at f32 and libm at f64, and
that is not an inconsistency: the f32 bodies work because every f32 with a
fraction fits in an i32, and at f64 that trick is gone.
abs-i32 and abs-i64 are Flan, one per width because min and max are builtins
and no generic covers the numeric types. pi and tau at both widths, written
out rather than derived so the compiler rounds each literal once.
programs/math3.flan covers it at values that are exact in binary, so nothing
pins one libm's last bit. The -O0 case is the one that matters: at -O2 LLVM
folds a call over two literals and leaves no symbol to resolve, which is how a
missing -lm hid the first time.
