[lld] [lld][ICF] Prevent merging two sections when they point to non-globals (PR #136641)

[Peter Smith via llvm-commits]

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@@ -356,6 +357,22 @@ static SmallVector<Symbol *> getRelocTargetSyms(const InputSection *sec) {
   return getReloc(sec, rel.relas);
 }
 
+// Checks if relocation has semantics beyond just the offset. We identify
+// such relocations to prevent ICF to preserve correctness.
+static bool isTrivialRelocationType(uint16_t emachine, RelType type) {
+  if (emachine == EM_AARCH64) {
+    switch (type) {
+    case R_AARCH64_GOT_LD_PREL19:
+    case R_AARCH64_LD64_GOTOFF_LO15:
+    case R_AARCH64_ADR_GOT_PAGE:
+    case R_AARCH64_LD64_GOT_LO12_NC:
+    case R_AARCH64_LD64_GOTPAGE_LO15:
+      return false;
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smithp35 wrote:

I'd expect it to break in GNU ld as that assumes that the sequence is emitted exactly. I've recently written that into the ABI in https://github.com/ARM-software/abi-aa/pull/311 (not merged yet).

Putting it here, would be more a philosophical "this is a non trivial relocation" rather than something that would make a practical difference. 

https://github.com/llvm/llvm-project/pull/136641