I think it's much nicer to have the test output inline in the source
file, that way it's much easier to review any changes. For example, when
escape analysis is improved this is visible with removed `// OUT` lines.
This is similar to how LLVM writes its tests, and I like that style.
Track whether an allocation reaches a callee return separately from the
instruction where it escapes. The extra result state is needed because LLVM's
returned parameter attribute only covers scalar returns: a slice helper returns
its data pointer inside a {ptr, len, cap} aggregate, so the alias is only
visible by walking insertvalue and ret uses in the callee.
This lets OptimizeAllocs keep the backing array for returnIntSlice(s) on the
stack when the returned slice is ignored, matching gc's escape decision for the
same pattern. The golden output still keeps the escaping returned-slice case on
the heap.
Follow returned pointer aliases when deciding whether runtime.alloc calls can
be lowered to stack allocations. A returned parameter is not the same as
nocapture: it still flows back to the caller and must be checked as an alias
of the original allocation.
Keep the analysis conservative for recursive returned-parameter chains and
unknown operands. The existing golden test now shows that the non-escaping
returned pointer cases no longer require heap allocation.
Add allocation diagnostics coverage for pointer-returning helpers, aggregate
slice returns, and conditional pointer returns before changing the allocation
optimizer.
The golden files record the current heap-allocation behavior so later commits
show exactly which diagnostics each optimizer improvement removes.
PR #5220 changed -print-allocs output to the go coverage tool format, which
replaced the original human-readable explanation of why each object had to be
heap allocated. That explanation is useful on its own, so this restores it as
the default behavior of -print-allocs and moves the coverage format behind a
-print-allocs-cover flag.
Signed-off-by: Piotr Bocheński <piotr@bochen.ski>
Ayke van Laethem
Jake Bailey
Piotr Bocheński