[clang] [llvm] [CodeGen][KCFI] Switch type hash from xxHash64 to FNV-1a (PR #167254)

[Sami Tolvanen via llvm-commits]

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@@ -3186,7 +3186,7 @@ void CodeGenModule::finalizeKCFITypes() {
       continue;
 
     std::string Asm = (".weak __kcfi_typeid_" + Name + "\n.set __kcfi_typeid_" +
-                       Name + ", " + Twine(Type->getZExtValue()) + "\n")
+                       Name + ", " + Twine(Type->getSExtValue()) + "\n")
----------------
samitolvanen wrote:

OK, testing with this change alone, x86_64 defconfig build fails:
```
ld.lld: error: vmlinux.o:(function __cfi___memcpy: .noinstr.text+0x4a21): relocation R_X86_64_32 out of range: 18446744071952041092 is not in [0, 4294967295]; references '__kcfi_typeid___memcpy'
>>> referenced by usercopy_64.c
>>> defined in vmlinux.o
...
```

https://github.com/llvm/llvm-project/pull/167254