[llvm] 0505181 - [X86] Fix to X86LoadValueInjectionRetHardeningPass for possible segfault

[Craig Topper via llvm-commits]

Author: Scott Constable
Date: 2020-04-10T18:28:08-07:00
New Revision: 0505181006f1088b2cb28a7240d5f27613783307

URL: https://github.com/llvm/llvm-project/commit/0505181006f1088b2cb28a7240d5f27613783307
DIFF: https://github.com/llvm/llvm-project/commit/0505181006f1088b2cb28a7240d5f27613783307.diff

LOG: [X86] Fix to X86LoadValueInjectionRetHardeningPass for possible segfault

`MBB.back()` could segfault if `MBB.empty()`. Fixed by checking for `MBB.empty()` in the loop.

Differential Revision: https://reviews.llvm.org/D77584

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp b/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
index 9c36e86099f9..6e1134a25950 100644
--- a/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
+++ b/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
@@ -99,6 +99,9 @@ bool X86LoadValueInjectionRetHardeningPass::runOnMachineFunction(
 
   bool Modified = false;
   for (auto &MBB : MF) {
+    if (MBB.empty())
+      continue;
+
     MachineInstr &MI = MBB.back();
     if (MI.getOpcode() != X86::RETQ)
       continue;