[PATCH] D116831: Initialize output parameter

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka created this revision.
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Or code like this have UB passing uninitialized CmpValue:

  int64_t CmpMask, CmpValue;
  if (!TII->analyzeCompare(MI, SrcReg, SrcReg2, CmpMask, CmpValue))
    return false;
  if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) {

Detected by msan with:
-Xclang -enable-noundef-analysis -mllvm -msan-eager-checks=1


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D116831

Files:
  llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp


Index: llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
===================================================================
--- llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
+++ llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
@@ -1893,6 +1893,7 @@
     case Hexagon::C4_cmplte:
     case Hexagon::C4_cmplteu:
       SrcReg2 = MI.getOperand(2).getReg();
+      Value = 0;
       return true;
 
     case Hexagon::C2_cmpeqi:


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