[clang] [compiler-rt] [ubsan] Display correct runtime messages for negative _BitInt (PR #96240)

[Björn Pettersson via cfe-commits]

================
@@ -125,6 +137,25 @@ class TypeDescriptor {
     return 1 << (TypeInfo >> 1);
   }
 
+  const char *getBitIntBitCountPointer() const {
+    DCHECK(isBitIntTy());
+    DCHECK(isSignedBitIntTy());
+    // Scan Name for zero and return the next address
+    const char *p = getTypeName();
+    while (*p != '\0')
+      ++p;
+    // Return the next address
+    return p + 1;
+  }
+
+  unsigned getIntegerBitCount() const {
+    DCHECK(isIntegerTy());
+    if (isSignedBitIntTy())
+      return *reinterpret_cast<const u32 *>(getBitIntBitCountPointer());
----------------
bjope wrote:

For example Value::getFloatValue() in ubsan_value.cpp is using internal_memcpy from sanitizer_libc. Maybe that is an option here.

https://github.com/llvm/llvm-project/pull/96240