[IRGen] Zero-init stack shadow copies of values at -Onone. #16564
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We already zero init AllocStack, and here's the same. The debugger's variable view shows up variables on the line where they're declared (before they've been initialized). In some cases, we just print garbage. In some others, it's dangerous (imagine an array which we believe has 2^32 elements because we ended up reusing a stack slot). This way it's always consistent, as lldb uses the first word to understand whether an object is initialized or not here. Fixes <rdar://problem/39883298>
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We already zero init AllocStack, and here's the same.
The debugger's variable view shows up variables on the line
where they're declared (before they've been initialized).
In some cases, we just print garbage. In some others, it's
dangerous (imagine an array which we believe has 2^32 elements
because we ended up reusing a stack slot). This way it's always
consistent, as lldb uses the first word to understand whether
an object is initialized or not here.
Fixes rdar://problem/39883298
Replace this paragraph with a description of your changes and rationale. Provide links to external references/discussions if appropriate.
Resolves SR-NNNN.