[clang] [clang][CodeGen] Zero init unspecified fields in initializers in C (PR #97121)

[via cfe-commits]

yabinc wrote:

> but maybe helpful if you can show Linux kernel codesize as a reference, to show there aren't massive issues.

I tested it on android-mainline, which closely follows linux upstream. The size change is very small.
.text 0x1139000 -> 0x1138000
.init.text 0x061f08 -> 0x062050
.data 0x20bec8 -> 0x20bf08

The linux kernel enables -ftrivial-auto-var-init=zero by default, which I guess already covers most (if not all) initialization instructions.


https://github.com/llvm/llvm-project/pull/97121