Make default initialization explicit

Coverity (a static analysis tool) reported that the emitted 'Features'
variable inside emitComputeAvailableFeatures in TableGen might be
unitialized.
Silence this warning by adding brackets for the default initialization.
Adapt test cases to take additional brackets into account.

Author: Martin Wehking

llvm/test/TableGen/GlobalISelEmitter.td

@@ -110,7 +110,7 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 
 // CHECK-LABEL: PredicateBitset MyTargetInstructionSelector::
 // CHECK-NEXT:  computeAvailableModuleFeatures(const MyTargetSubtarget *Subtarget) const {
-// CHECK-NEXT:    PredicateBitset Features;
+// CHECK-NEXT:    PredicateBitset Features{};
 // CHECK-NEXT:    if (Subtarget->hasA())
 // CHECK-NEXT:      Features.set(Feature_HasABit);
 // CHECK-NEXT:    if (Subtarget->hasB())
@@ -120,7 +120,7 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 
 // CHECK-LABEL: PredicateBitset MyTargetInstructionSelector::
 // CHECK-NEXT:  computeAvailableFunctionFeatures(const MyTargetSubtarget *Subtarget, const MachineFunction *MF) const {
-// CHECK-NEXT:    PredicateBitset Features;
+// CHECK-NEXT:    PredicateBitset Features{};
 // CHECK-NEXT:    if (Subtarget->hasC())
 // CHECK-NEXT:      Features.set(Feature_HasCBit);
 // CHECK-NEXT:    return Features;

llvm/test/TableGen/GlobalISelEmitterHwModes.td

@@ -85,7 +85,7 @@ class I<dag OOps, dag IOps, list<dag> Pat>
 
 // CHECK-LABEL: PredicateBitset MyTargetInstructionSelector::
 // CHECK-NEXT:  computeAvailableModuleFeatures(const MyTargetSubtarget *Subtarget) const {
-// CHECK-NEXT:    PredicateBitset Features;
+// CHECK-NEXT:    PredicateBitset Features{};
 // CHECK-NEXT:    if (!((Subtarget->has64())))
 // CHECK-NEXT:      Features.set(Feature_HwMode1Bit);
 // CHECK-NEXT:    if ((Subtarget->has64()))
@@ -95,7 +95,7 @@ class I<dag OOps, dag IOps, list<dag> Pat>
 
 // CHECK-LABEL: PredicateBitset MyTargetInstructionSelector::
 // CHECK-NEXT:  computeAvailableFunctionFeatures(const MyTargetSubtarget *Subtarget, const MachineFunction *MF) const {
-// CHECK-NEXT:    PredicateBitset Features;
+// CHECK-NEXT:    PredicateBitset Features{};
 // CHECK-NEXT:    return Features;
 // CHECK-NEXT:  }
 

llvm/utils/TableGen/Common/SubtargetFeatureInfo.cpp

@@ -108,7 +108,7 @@ void SubtargetFeatureInfo::emitComputeAvailableFeatures(
   if (!ExtraParams.empty())
     OS << ", " << ExtraParams;
   OS << ") const {\n";
-  OS << "  PredicateBitset Features;\n";
+  OS << "  PredicateBitset Features{};\n";
   for (const auto &SF : SubtargetFeatures) {
     const SubtargetFeatureInfo &SFI = SF.second;
     StringRef CondStr = SFI.TheDef->getValueAsString("CondString");