Clean up static analyzer warnings.

Clang's static analyzer found several potential cases of undefined
behavior, use of un-initialized values, and potentially null pointer
dereferences in tablegen, Support, MC, and ADT. This cleans them up
with specific assertions on the assumptions of the code.

llvm-svn: 224154

3 files changed, 11 insertions, 6 deletions

diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index 84eb0937765..a4f82a742dd 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -682,7 +682,10 @@ void MCAsmStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
       // We truncate our partial emission to fit within the bounds of the
       // emission domain.  This produces nicer output and silences potential
       // truncation warnings when round tripping through another assembler.
-      ValueToEmit &= ~0ULL >> (64 - EmissionSize * 8);
+      uint64_t Shift = 64 - EmissionSize * 8;
+      assert(Shift < std::numeric_limits<unsigned long long>::digits &&
+             "undefined behavior");
+      ValueToEmit &= ~0ULL >> Shift;
       EmitIntValue(ValueToEmit, EmissionSize);
       Emitted += EmissionSize;
     }
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 21e68678e75..08fe5017bd5 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -405,7 +405,9 @@ void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
 }
 
 void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
-  unsigned ItemSize = getCurrentSection().first->isVirtualSection() ? 0 : 1;
+  const MCSection *Sec = getCurrentSection().first;
+  assert(Sec && "need a section");
+  unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1;
   insert(new MCFillFragment(0, ItemSize, NumBytes));
 }
 
diff --git a/llvm/lib/MC/MCParser/COFFAsmParser.cpp b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
index 6f82e6ef3e4..18bdb03336a 100644
--- a/llvm/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
@@ -582,7 +582,7 @@ bool COFFAsmParser::ParseSEHDirectiveHandlerData(StringRef, SMLoc) {
 }
 
 bool COFFAsmParser::ParseSEHDirectivePushReg(StringRef, SMLoc L) {
-  unsigned Reg;
+  unsigned Reg = 0;
   if (ParseSEHRegisterNumber(Reg))
     return true;
 
@@ -595,7 +595,7 @@ bool COFFAsmParser::ParseSEHDirectivePushReg(StringRef, SMLoc L) {
 }
 
 bool COFFAsmParser::ParseSEHDirectiveSetFrame(StringRef, SMLoc L) {
-  unsigned Reg;
+  unsigned Reg = 0;
   int64_t Off;
   if (ParseSEHRegisterNumber(Reg))
     return true;
@@ -636,7 +636,7 @@ bool COFFAsmParser::ParseSEHDirectiveAllocStack(StringRef, SMLoc) {
 }
 
 bool COFFAsmParser::ParseSEHDirectiveSaveReg(StringRef, SMLoc L) {
-  unsigned Reg;
+  unsigned Reg = 0;
   int64_t Off;
   if (ParseSEHRegisterNumber(Reg))
     return true;
@@ -663,7 +663,7 @@ bool COFFAsmParser::ParseSEHDirectiveSaveReg(StringRef, SMLoc L) {
 // FIXME: This method is inherently x86-specific. It should really be in the
 // x86 backend.
 bool COFFAsmParser::ParseSEHDirectiveSaveXMM(StringRef, SMLoc L) {
-  unsigned Reg;
+  unsigned Reg = 0;
   int64_t Off;
   if (ParseSEHRegisterNumber(Reg))
     return true;