[PATCH] D63285: [RISCV] Fix a potential issue in shouldInsertFixupForCodeAlign()

[Edward Jones via Phabricator via llvm-commits]

edward-jones created this revision.
edward-jones added reviewers: asb, lewis-revill.
Herald added subscribers: llvm-commits, Jim, benna, psnobl, jocewei, PkmX, rkruppe, the_o, brucehoult, MartinMosbeck, rogfer01, zzheng, jrtc27, shiva0217, kito-cheng, niosHD, sabuasal, apazos, simoncook, johnrusso, rbar.
Herald added a project: LLVM.

The bool result of shouldInsertExtraNopBytesForCodeAlign() is not checked but the returned nop count is unconditionally read even though it could be uninitialized.


Repository:
  rL LLVM

https://reviews.llvm.org/D63285

Files:
  lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp


Index: lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
===================================================================
--- lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
+++ lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
@@ -333,11 +333,10 @@
   if (!STI.getFeatureBits()[RISCV::FeatureRelax])
     return false;
 
-  // Calculate total Nops we need to insert.
+  // Calculate total Nops we need to insert. If there are none to insert
+  // then simply return.
   unsigned Count;
-  shouldInsertExtraNopBytesForCodeAlign(AF, Count);
-  // No Nop need to insert, simply return.
-  if (Count == 0)
+  if (!shouldInsertExtraNopBytesForCodeAlign(AF, Count) || (Count == 0))
     return false;
 
   MCContext &Ctx = Asm.getContext();


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