[PATCH] D130922: [InstCombine] Add support for stpncpy folding

[Martin Sebor via Phabricator via llvm-commits]

msebor planned changes to this revision.
msebor added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:699
   Value *Size = CI->getArgOperand(2);
   annotateNonNullNoUndefBasedOnAccess(CI, 0);
   if (isKnownNonZero(Size, DL))
----------------
Both `stpncpy` and `strncpy` access the destination only when `Size` is nonzero but not otherwise.  (Annotating the argument unconditionally is a pre-existing bug in the code.)


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:784
+
+  Value *Off = B.getInt64(SrcLen);
+  return B.CreateInBoundsGEP(B.getInt8Ty(), Dst, Off, "endptr");
----------------
`stpncpy(D, S, N)` returns `D + min(strlen(S), N)` as documented but not correctly verified in the new `stpcpy-1.ll` test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130922/new/

https://reviews.llvm.org/D130922