[PATCH] D41723: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715, "Branch Target Injection", and is one of the two halves to Spectre..

[Andrei via Phabricator via llvm-commits]

AndreiGrischenko added inline comments.


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Comment at: llvm/lib/Target/X86/X86InstrCompiler.td:1160
           (TCRETURNdi tglobaladdr:$dst, imm:$off)>,
-          Requires<[NotLP64]>;
+          Requires<[NotLP64, NotUseRetpoline]>;
 
----------------
Hi Chandler,
Do you really want to use "NotUseRetpoline" here? It will match RETPOLINE_TCRETURN32 then even it is not an indirect branch.
I guess the following test case will crash llc.

```
target triple = "i386-unknown-linux-gnu"

define void @FOO() {
  ret void
}

define void @FOO1() {
entry:
  tail call void @FOO()
  ret void
}
```



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Comment at: llvm/lib/Target/X86/X86RetpolineThunks.cpp:121
+
+    createThunk(M, "r11", X86::R11);
+  } else {
----------------
You will create thunk function even if it is not necessary? For example for " tail call void @FOO()"?




https://reviews.llvm.org/D41723