diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -52,6 +52,7 @@
 
 CODEGENOPT(DisableFree       , 1, 0) ///< Don't free memory.
 CODEGENOPT(DiscardValueNames , 1, 0) ///< Discard Value Names from the IR (LLVMContext flag)
+CODEGENOPT(DisableNoundefArgs , 1, 0) ///< Disable emitting `noundef` attributes on IR call arguments
 CODEGENOPT(DisableGCov       , 1, 0) ///< Don't run the GCov pass, for testing.
 CODEGENOPT(DisableLLVMPasses , 1, 0) ///< Don't run any LLVM IR passes to get
                                      ///< the pristine IR generated by the
diff --git a/clang/include/clang/Driver/CC1Options.td b/clang/include/clang/Driver/CC1Options.td
--- a/clang/include/clang/Driver/CC1Options.td
+++ b/clang/include/clang/Driver/CC1Options.td
@@ -509,6 +509,8 @@
   HelpText<"Disable freeing of memory on exit">;
 def discard_value_names : Flag<["-"], "discard-value-names">,
   HelpText<"Discard value names in LLVM IR">;
+def disable_noundef_args : Flag<["-"], "disable-noundef-args">,
+  HelpText<"Disable emitting noundef attribute in LLVM IR">;
 def load : Separate<["-"], "load">, MetaVarName<"<dsopath>">,
   HelpText<"Load the named plugin (dynamic shared object)">;
 def plugin : Separate<["-"], "plugin">, MetaVarName<"<name>">,
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1876,6 +1876,33 @@
   llvm::for_each(NBA->builtinNames(), AddNoBuiltinAttr);
 }
 
+static bool DetermineNoUndef(QualType QTy, CodeGenTypes &Types,
+                             const llvm::DataLayout &DL, const ABIArgInfo &AI) {
+  llvm::Type *Ty = Types.ConvertTypeForMem(QTy);
+  if (AI.getKind() == ABIArgInfo::Indirect)
+    return true;
+  if (AI.getKind() == ABIArgInfo::Extend)
+    return true;
+  if (!DL.typeSizeEqualsStoreSize(Ty))
+    return false;
+  if (QTy->isExtIntType())
+    return true;
+  if (QTy->isReferenceType())
+    return true;
+  if (QTy->isScalarType()) {
+    if (const ComplexType *Complex = dyn_cast<ComplexType>(QTy))
+      return DetermineNoUndef(Complex->getElementType(), Types, DL, AI);
+    return true;
+  }
+  if (const VectorType *Vector = dyn_cast<VectorType>(QTy))
+    return DetermineNoUndef(Vector->getElementType(), Types, DL, AI);
+  if (const MatrixType *Matrix = dyn_cast<MatrixType>(QTy))
+    return DetermineNoUndef(Matrix->getElementType(), Types, DL, AI);
+  if (const ArrayType *Array = dyn_cast<ArrayType>(QTy))
+    return DetermineNoUndef(Array->getElementType(), Types, DL, AI);
+  return false;
+}
+
 /// Construct the IR attribute list of a function or call.
 ///
 /// When adding an attribute, please consider where it should be handled:
@@ -2075,6 +2102,14 @@
 
   QualType RetTy = FI.getReturnType();
   const ABIArgInfo &RetAI = FI.getReturnInfo();
+  const llvm::DataLayout &DL = getDataLayout();
+
+  // Determine if the return type could be partially undef
+  if (!RetTy->isVoidType() && RetAI.getKind() != ABIArgInfo::Indirect &&
+      DetermineNoUndef(RetTy, getTypes(), DL, RetAI)) {
+    RetAttrs.addAttribute(llvm::Attribute::NoUndef);
+  }
+
   switch (RetAI.getKind()) {
   case ABIArgInfo::Extend:
     if (RetAI.isSignExt())
@@ -2160,6 +2195,12 @@
       }
     }
 
+    // Decide whether the argument we're handling could be partially undef
+    bool ArgNoUndef = DetermineNoUndef(ParamType, getTypes(), DL, AI);
+    if (!CodeGenOpts.DisableNoundefArgs && ArgNoUndef) {
+      Attrs.addAttribute(llvm::Attribute::NoUndef);
+    }
+
     // 'restrict' -> 'noalias' is done in EmitFunctionProlog when we
     // have the corresponding parameter variable.  It doesn't make
     // sense to do it here because parameters are so messed up.
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -925,6 +925,7 @@
 
   Opts.DisableFree = Args.hasArg(OPT_disable_free);
   Opts.DiscardValueNames = Args.hasArg(OPT_discard_value_names);
+  Opts.DisableNoundefArgs = Args.hasArg(OPT_disable_noundef_args);
   Opts.DisableTailCalls = Args.hasArg(OPT_mdisable_tail_calls);
   Opts.NoEscapingBlockTailCalls =
       Args.hasArg(OPT_fno_escaping_block_tail_calls);
diff --git a/clang/test/CodeGen/indirect-noundef.c b/clang/test/CodeGen/indirect-noundef.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/indirect-noundef.c
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -O0 -emit-llvm -o - %s | FileCheck %s
+
+union u1 { int val; };
+
+// CHECK: @indirect_callee_int_ptr = global i32 (i32)*
+int (*indirect_callee_int_ptr)(int);
+// CHECK: @indirect_callee_union_ptr = global i32 (i32)*
+union u1 (*indirect_callee_union_ptr)(union u1);
+
+// CHECK-LABEL: define noundef i32 @indirect_callee_int(i32 noundef %
+int indirect_callee_int(int a) { return a; }
+// CHECK-LABEL: define i32 @indirect_callee_union(i32 %
+union u1 indirect_callee_union(union u1 a) { return a; }
+
+int main() {
+    // CHECK: call noundef i32 @indirect_callee_int(i32 noundef 0)
+    indirect_callee_int(0);
+    // CHECK: call i32 @indirect_callee_union(i32 %
+    indirect_callee_union((union u1){0});
+
+    indirect_callee_int_ptr = indirect_callee_int;
+    indirect_callee_union_ptr = indirect_callee_union;
+
+    // CHECK: call noundef i32 %{{.*}}(i32 noundef 0)
+    indirect_callee_int_ptr(0);
+    // CHECK: call i32 %{{.*}}(i32 %
+    indirect_callee_union_ptr((union u1){});
+
+    return 0;
+}
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -643,6 +643,7 @@
   ATTR_KIND_PREALLOCATED = 65,
   ATTR_KIND_NO_MERGE = 66,
   ATTR_KIND_NULL_POINTER_IS_VALID = 67,
+  ATTR_KIND_NOUNDEF = 68,
 };
 
 enum ComdatSelectionKindCodes {
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/llvm/include/llvm/IR/Attributes.td
@@ -39,6 +39,9 @@
 /// Pass structure by value.
 def ByVal : TypeAttr<"byval">;
 
+/// Parameter or return value may not contain uninitialized or poison bits
+def NoUndef : EnumAttr<"noundef">;
+
 /// Marks function as being in a cold path.
 def Cold : EnumAttr<"cold">;
 
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -696,6 +696,7 @@
   KEYWORD(writeonly);
   KEYWORD(zeroext);
   KEYWORD(immarg);
+  KEYWORD(noundef);
 
   KEYWORD(type);
   KEYWORD(opaque);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1374,6 +1374,7 @@
     case lltok::kw_inalloca:
     case lltok::kw_nest:
     case lltok::kw_noalias:
+    case lltok::kw_noundef:
     case lltok::kw_nocapture:
     case lltok::kw_nonnull:
     case lltok::kw_returned:
@@ -1677,6 +1678,9 @@
     case lltok::kw_inalloca:        B.addAttribute(Attribute::InAlloca); break;
     case lltok::kw_inreg:           B.addAttribute(Attribute::InReg); break;
     case lltok::kw_nest:            B.addAttribute(Attribute::Nest); break;
+    case lltok::kw_noundef:
+      B.addAttribute(Attribute::NoUndef);
+      break;
     case lltok::kw_noalias:         B.addAttribute(Attribute::NoAlias); break;
     case lltok::kw_nocapture:       B.addAttribute(Attribute::NoCapture); break;
     case lltok::kw_nofree:          B.addAttribute(Attribute::NoFree); break;
@@ -1774,6 +1778,9 @@
     }
     case lltok::kw_inreg:           B.addAttribute(Attribute::InReg); break;
     case lltok::kw_noalias:         B.addAttribute(Attribute::NoAlias); break;
+    case lltok::kw_noundef:
+      B.addAttribute(Attribute::NoUndef);
+      break;
     case lltok::kw_nonnull:         B.addAttribute(Attribute::NonNull); break;
     case lltok::kw_signext:         B.addAttribute(Attribute::SExt); break;
     case lltok::kw_zeroext:         B.addAttribute(Attribute::ZExt); break;
diff --git a/llvm/lib/AsmParser/LLToken.h b/llvm/lib/AsmParser/LLToken.h
--- a/llvm/lib/AsmParser/LLToken.h
+++ b/llvm/lib/AsmParser/LLToken.h
@@ -196,6 +196,7 @@
   kw_naked,
   kw_nest,
   kw_noalias,
+  kw_noundef,
   kw_nobuiltin,
   kw_nocapture,
   kw_noduplicate,
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1530,6 +1530,8 @@
     return Attribute::SanitizeMemTag;
   case bitc::ATTR_KIND_PREALLOCATED:
     return Attribute::Preallocated;
+  case bitc::ATTR_KIND_NOUNDEF:
+    return Attribute::NoUndef;
   }
 }
 
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -731,6 +731,8 @@
     return bitc::ATTR_KIND_SANITIZE_MEMTAG;
   case Attribute::Preallocated:
     return bitc::ATTR_KIND_PREALLOCATED;
+  case Attribute::NoUndef:
+    return bitc::ATTR_KIND_NOUNDEF;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None:
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -443,6 +443,8 @@
     return "cold";
   if (hasAttribute(Attribute::ImmArg))
     return "immarg";
+  if (hasAttribute(Attribute::NoUndef))
+    return "noundef";
 
   if (hasAttribute(Attribute::ByVal)) {
     std::string Result;
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -877,6 +877,7 @@
       case Attribute::NoMerge:
       case Attribute::NoReturn:
       case Attribute::NoSync:
+      case Attribute::NoUndef:
       case Attribute::None:
       case Attribute::NonNull:
       case Attribute::Preallocated: