[llvm] [BOLT] Gadget scanner: detect non-protected indirect calls (PR #131899)

[Anatoly Trosinenko via llvm-commits]

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@@ -277,6 +277,33 @@ class AArch64MCPlusBuilder : public MCPlusBuilder {
     }
   }
 
+  MCPhysReg
+  getRegUsedAsCallDest(const MCInst &Inst,
+                       bool &IsAuthenticatedInternally) const override {
+    assert(isCall(Inst) || isBranch(Inst));
+    IsAuthenticatedInternally = false;
+
+    switch (Inst.getOpcode()) {
+    case AArch64::BR:
+    case AArch64::BLR:
+      return Inst.getOperand(0).getReg();
+    case AArch64::BRAA:
+    case AArch64::BRAB:
+    case AArch64::BRAAZ:
+    case AArch64::BRABZ:
+    case AArch64::BLRAA:
+    case AArch64::BLRAB:
+    case AArch64::BLRAAZ:
+    case AArch64::BLRABZ:
+      IsAuthenticatedInternally = true;
+      return Inst.getOperand(0).getReg();
+    default:
+      if (isIndirectCall(Inst) || isIndirectBranch(Inst))
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atrosinenko wrote:

My idea is to update #133227 (which targets the `main` branch) after merging this PR and then mark it as ready for review. The initial version was uploaded more as a reminder to myself - that is the reason why it is created as a draft PR. As far as I understand, opening a draft PR does not automatically notify anyone, so it should be harmless from the perspective of disturbing the reviewers.

Note that #133227 is targeted to `main` branch, thus its merge target does not have the changes from this PR yet. Another approach could be to manually stack that PR on top of this one instead of `main` (or maybe Graphite supports arbitrary trees of PRs) - I just didn't tried to make everything as efficient as possible, but just to have a reminder and not to disturb the reviewers unless #133227 is finally ready.

https://github.com/llvm/llvm-project/pull/131899