[analyzer] Fix crash analyzing _BitInt() in evalIntegralCast (llvm#66782

)

evalIntegralCast was using makeIntVal, and when _BitInt() types were
introduced this exposed a crash in evalIntegralCast as a result.

This is a reapply of a previous patch that failed post merge on the arm
buildbots, because arm cannot handle large
BitInts. Pinning the triple for the testcase solves that problem. 

Improve evalIntegralCast to use makeIntVal more efficiently to avoid the
crash exposed by use of _BitInt.

This was caught with our internal randomized testing.

<src-root>/llvm/include/llvm/ADT/APInt.h:1510:
  int64_t llvm::APInt::getSExtValue() const: Assertion
  `getSignificantBits() <= 64 && "Too many bits for int64_t"' failed.a

...
 #9 <address> llvm::APInt::getSExtValue() const
  <src-root>/llvm/include/llvm/ADT/APInt.h:1510:5
  llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>,
  clang::ento::SVal, clang::QualType, clang::QualType)
  <src-root>/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp:607:24
clang::Expr const*, clang::ento::ExplodedNode*,
clang::ento::ExplodedNodeSet&)
  <src-root>/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp:413:61
...

 Fixes: llvm#61960

 Reviewed By: donat.nagy

clang/lib/StaticAnalyzer/Core/SValBuilder.cpp

@@ -598,11 +598,9 @@ SVal SValBuilder::evalIntegralCast(ProgramStateRef state, SVal val,
   APSIntType ToType(getContext().getTypeSize(castTy),
                     castTy->isUnsignedIntegerType());
   llvm::APSInt ToTypeMax = ToType.getMaxValue();
-  NonLoc ToTypeMaxVal =
-      makeIntVal(ToTypeMax.isUnsigned() ? ToTypeMax.getZExtValue()
-                                        : ToTypeMax.getSExtValue(),
-                 castTy)
-          .castAs<NonLoc>();
+
+  NonLoc ToTypeMaxVal = makeIntVal(ToTypeMax);
+
   // Check the range of the symbol being casted against the maximum value of the
   // target type.
   NonLoc FromVal = val.castAs<NonLoc>();

clang/test/Analysis/bitint-no-crash.c

@@ -0,0 +1,13 @@
+ // RUN: %clang_analyze_cc1 -analyzer-checker=core \
+ // RUN:   -analyzer-checker=debug.ExprInspection \
+ // RUN:   -triple x86_64-pc-linux-gnu \
+ // RUN:   -verify %s
+
+// Don't crash when using _BitInt(). Pin to the x86_64 triple for now,
+// since not all architectures support _BitInt()
+// expected-no-diagnostics
+_BitInt(256) a;
+_BitInt(129) b;
+void c() {
+  b = a;
+}