[llvm] Use static_assert on getEmptyKey and getTombstoneKey (NFC) (#167167)

Note that DenseMapInfo<unsigned>::getEmptyKey() and getTombstoneKey()
are constexpr.

This patch removes assertion messages as they don't state any more
than what's expressed in the assertion condition.

Identified with misc-static-assert.

Author: kazutakahirata

llvm/include/llvm/Analysis/IRSimilarityIdentifier.h

@@ -509,11 +509,10 @@ struct IRInstructionMapper {
       : InstDataAllocator(IDA), IDLAllocator(IDLA) {
     // Make sure that the implementation of DenseMapInfo<unsigned> hasn't
     // changed.
-    assert(DenseMapInfo<unsigned>::getEmptyKey() == static_cast<unsigned>(-1) &&
-           "DenseMapInfo<unsigned>'s empty key isn't -1!");
-    assert(DenseMapInfo<unsigned>::getTombstoneKey() ==
-               static_cast<unsigned>(-2) &&
-           "DenseMapInfo<unsigned>'s tombstone key isn't -2!");
+    static_assert(DenseMapInfo<unsigned>::getEmptyKey() ==
+                  static_cast<unsigned>(-1));
+    static_assert(DenseMapInfo<unsigned>::getTombstoneKey() ==
+                  static_cast<unsigned>(-2));
 
     IDL = new (IDLAllocator->Allocate())
         IRInstructionDataList();

llvm/include/llvm/Transforms/IPO/IROutliner.h

@@ -204,10 +204,10 @@ class IROutliner {
       : getTTI(GTTI), getIRSI(GIRSI), getORE(GORE) {
 
     // Check that the DenseMap implementation has not changed.
-    assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
-           "DenseMapInfo<unsigned>'s empty key isn't -1!");
-    assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
-           "DenseMapInfo<unsigned>'s tombstone key isn't -2!");
+    static_assert(DenseMapInfo<unsigned>::getEmptyKey() ==
+                  static_cast<unsigned>(-1));
+    static_assert(DenseMapInfo<unsigned>::getTombstoneKey() ==
+                  static_cast<unsigned>(-2));
   }
   bool run(Module &M);
 

llvm/lib/CodeGen/MachineOutliner.cpp

@@ -420,10 +420,10 @@ struct InstructionMapper {
   InstructionMapper(const MachineModuleInfo &MMI_) : MMI(MMI_) {
     // Make sure that the implementation of DenseMapInfo<unsigned> hasn't
     // changed.
-    assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
-           "DenseMapInfo<unsigned>'s empty key isn't -1!");
-    assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
-           "DenseMapInfo<unsigned>'s tombstone key isn't -2!");
+    static_assert(DenseMapInfo<unsigned>::getEmptyKey() ==
+                  static_cast<unsigned>(-1));
+    static_assert(DenseMapInfo<unsigned>::getTombstoneKey() ==
+                  static_cast<unsigned>(-2));
   }
 };