[clang] [llvm] [LFI] Add MCLFIRewriter infrastructure (PR #172906)

[Alexis Engelke via cfe-commits]

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@@ -390,6 +391,10 @@ bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
 
 void MCObjectStreamer::emitInstruction(const MCInst &Inst,
                                        const MCSubtargetInfo &STI) {
+  if (LFIRewriter && LFIRewriter->isEnabled() &&
+      LFIRewriter->rewriteInst(Inst, *this, STI))
+    return;
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aengelke wrote:

How is this supposed to work? What exactly does rewriteInst do? How does it emit the instruction?

Can we fold this into a single function call?

https://github.com/llvm/llvm-project/pull/172906