diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -472,6 +472,26 @@
       if (!llvm::zlib::isAvailable())
         return make_error<InstrProfError>(instrprof_error::zlib_unavailable);
 
+      // Sanity-check the uncompressed size. If the data is corrupted, then we
+      // could run into a situation where we attempt to malloc a large amount of
+      // data and OOM (see PR51628). While we technically do not have a way to
+      // error-check if the size is actually "correct", we can at least guess
+      // beforehand if the data is corrupt by comparing the uncompressed size to
+      // the compressed size. If the ratio is large enough, then we can warn.
+      //
+      // https://zlib.net/zlib_tech.html stats that typical zlib compression
+      // factors are in the range of 2:1 and 5:1. The value used here should be
+      // large enough such that we minimize the number of "false positives" from
+      // decompressions that we can properly allocate for.
+      constexpr size_t CompressionRatio = 10;
+      if (UncompressedSize > CompressedSize * CompressionRatio) {
+        llvm::errs()
+            << "warning: the uncompressed size is more than "
+            << CompressionRatio
+            << "x the size of the compressed size, which could indicate data "
+               "corruption in the uncompressed size and lead to an OOM error\n";
+      }
+
       StringRef CompressedNameStrings(reinterpret_cast<const char *>(P),
                                       CompressedSize);
       if (Error E =