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

[Phoebe Wang via llvm-commits]

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@@ -0,0 +1,34 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=x86_64-linux-gnu -mattr=-sse,-avx | FileCheck %s
+
+ at .str = private unnamed_addr constant [6 x i8] c"%d %d\00", align 1
+
+define void @caller(i32 %0, i32 %1) #0 {
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phoebewang wrote:

Okay, but it also mentions:

> Functions specified with the ‘no_caller_saved_registers’ attribute should only call other functions with the ‘no_caller_saved_registers’ attribute, or should be compiled with the ‘-mgeneral-regs-only’ flag to avoid saving unused non-GPR registers.

So is it a rational scenario? Or we should consider more like https://godbolt.org/z/Eqnh5W1en

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