[PATCH] D62109: [RegisterCoalescer] fix potential use of undef value. NFC

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers created this revision.
nickdesaulniers added a reviewer: wmi.
Herald added subscribers: llvm-commits, tpr, hiraditya, qcolombet, MatzeB.
Herald added a project: LLVM.

Fixes a warning produced from scan-build (llvm.org/reports/scan-build/),
further warnings found by annotation isMoveInstr [[nodiscard]].

isMoveInstr potentially does not assign to its parameters, so if they
were uninitialized, they will potentially stay uninitialized.  It seems
most call sites pass references to uninitialized values, then use them
without checking the return value.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62109

Files:
  llvm/lib/CodeGen/RegisterCoalescer.cpp


Index: llvm/lib/CodeGen/RegisterCoalescer.cpp
===================================================================
--- llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -1516,7 +1516,8 @@
   // CoalescerPair may have a new register class with adjusted subreg indices
   // at this point.
   unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
-  isMoveInstr(*TRI, CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx);
+  if(!isMoveInstr(*TRI, CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx))
+    return nullptr;
 
   SlotIndex Idx = LIS->getInstructionIndex(*CopyMI);
   const LiveInterval &SrcLI = LIS->getInterval(SrcReg);
@@ -3512,7 +3513,8 @@
   if (!UseTerminalRule)
     return false;
   unsigned DstReg, DstSubReg, SrcReg, SrcSubReg;
-  isMoveInstr(*TRI, &Copy, SrcReg, DstReg, SrcSubReg, DstSubReg);
+  if (!isMoveInstr(*TRI, &Copy, SrcReg, DstReg, SrcSubReg, DstSubReg))
+    return false;
   // Check if the destination of this copy has any other affinity.
   if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
       // If SrcReg is a physical register, the copy won't be coalesced.
@@ -3536,8 +3538,9 @@
     if (&MI == &Copy || !MI.isCopyLike() || MI.getParent() != OrigBB)
       continue;
     unsigned OtherReg, OtherSubReg, OtherSrcReg, OtherSrcSubReg;
-    isMoveInstr(*TRI, &Copy, OtherSrcReg, OtherReg, OtherSrcSubReg,
-                OtherSubReg);
+    if (!isMoveInstr(*TRI, &Copy, OtherSrcReg, OtherReg, OtherSrcSubReg,
+                OtherSubReg))
+      return false;
     if (OtherReg == SrcReg)
       OtherReg = OtherSrcReg;
     // Check if OtherReg is a non-terminal.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D62109.200186.patch
Type: text/x-patch
Size: 1625 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190519/826cd27f/attachment.bin>