StackIR local2stack: Make sure we do not break non-nullable validation (#5919)

local2stack removes a pair of

local.set 0
local.get 0

when that set is not used anywhere else: whatever value is put into the local,
we can just leave it on the stack to replace the get. However, we only handled
actual uses of the set which we checked using LocalGraph. There may be code
that does not actually use the set local, but needs that set purely for validation
reasons:

local.set 0
local.get 0
block
  local.set 0
end
local.get

That last get reads the value set in the block, so the first set is not used by it.
But for validation purposes, the inner set stops helping at the block end, so
we do need that initial set.

To fix this, check for gets that need our set to validate before removing any.

Fixes #5917

0 files changed, 0 insertions, 0 deletions