[clang] [Clang] Add fake use emission to Clang with -fextend-lifetimes (PR #110102)

[David Blaikie via cfe-commits]

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@@ -1353,6 +1353,19 @@ void CodeGenFunction::EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr) {
   C->setDoesNotThrow();
 }
 
+void CodeGenFunction::EmitFakeUse(Address Addr) {
+  // We do not emit a fake use if we want to apply optnone to this function,
+  // even if we might not apply it anyway due to minsize or similar attributes.
+  if (!CGM.getCodeGenOpts().DisableO0ImplyOptNone &&
+      CGM.getCodeGenOpts().OptimizationLevel == 0)
+    return;
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dwblaikie wrote:

(might be worth removing "-disable-O0-optnone" as it's a bit of a hazard for reasons like this - if folks want optimizable IR, but without optimizations applied, they'd probably be better off disabling optimizations (`-disable-llvm-optzns`) I think?)

https://github.com/llvm/llvm-project/pull/110102