[PATCH] D89612: NFC: Fix -Wsign-compare warnings on 32-bit builds

[Hubert Tong via Phabricator via llvm-commits]

hubert.reinterpretcast created this revision.
hubert.reinterpretcast added reviewers: dantrushin, hokein, daltenty, stevewan, jasonliu.
Herald added a subscriber: hiraditya.
Herald added projects: clang, LLVM.
hubert.reinterpretcast requested review of this revision.

Comparing 32-bit `ptrdiff_t` against 32-bit `unsigned` results in `-Wsign-compare` warnings for both GCC and Clang.

The warning for the cases in question appear to identify an issue where the `ptrdiff_t` value would be mutated via conversion to an unsigned type.

The warning is resolved by using the usual arithmetic conversions to safely preserve the value of the `unsigned` operand while trying to convert to a signed type. Host platforms where `unsigned` has the same width as `unsigned long long` will need to make a different change, but using an explicit cast has disadvantages that can be avoided for now.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D89612

Files:
  clang/lib/Serialization/ASTReaderStmt.cpp
  llvm/lib/CodeGen/StackMaps.cpp


Index: llvm/lib/CodeGen/StackMaps.cpp
===================================================================
--- llvm/lib/CodeGen/StackMaps.cpp
+++ llvm/lib/CodeGen/StackMaps.cpp
@@ -401,7 +401,7 @@
     SmallVector<unsigned, 8> GCPtrIndices;
     unsigned GCPtrIdx = (unsigned)SO.getFirstGCPtrIdx();
     assert((int)GCPtrIdx != -1);
-    assert(MOI - MI.operands_begin() == GCPtrIdx);
+    assert(MOI - MI.operands_begin() == GCPtrIdx + 0LL);
     while (NumGCPointers--) {
       GCPtrIndices.push_back(GCPtrIdx);
       GCPtrIdx = StackMaps::getNextMetaArgIdx(&MI, GCPtrIdx);
Index: clang/lib/Serialization/ASTReaderStmt.cpp
===================================================================
--- clang/lib/Serialization/ASTReaderStmt.cpp
+++ clang/lib/Serialization/ASTReaderStmt.cpp
@@ -2186,9 +2186,9 @@
   unsigned NumArgs = Record.readInt();
   E->BeginLoc = readSourceLocation();
   E->EndLoc = readSourceLocation();
-  assert(
-      (NumArgs == std::distance(E->children().begin(), E->children().end())) &&
-      "Wrong NumArgs!");
+  assert((NumArgs + 0LL ==
+          std::distance(E->children().begin(), E->children().end())) &&
+         "Wrong NumArgs!");
   (void)NumArgs;
   for (Stmt *&Child : E->children())
     Child = Record.readSubStmt();


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