[llvm] [X86] Do not elect to tail call if caller must preserve all registers (PR #112098)

[Nikita Popov via llvm-commits]

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@@ -2856,6 +2856,14 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(
       return false;
   }
 
+  // The stack frame of the caller cannot be replaced by the tail-callee one's
+  // if the function is required to preserve all the registers. Conservatively
+  // prevent tail optimization even if hypothetically all the registers are used
+  // for passing formal parameters or returning values.
+  if (CLI.CB &&
+      CLI.CB->getFunction()->hasFnAttribute("no_caller_saved_registers"))
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nikic wrote:

Can this check MF.getFunction() instead of the optional CLI.CB?

https://github.com/llvm/llvm-project/pull/112098