diff --git a/src/tint/lang/core/ir/function.cc b/src/tint/lang/core/ir/function.cc
index f8a3e53..2cce808 100644
--- a/src/tint/lang/core/ir/function.cc
+++ b/src/tint/lang/core/ir/function.cc
@@ -71,8 +71,10 @@
     }
     params_ = std::move(params);
     TINT_ASSERT(!params_.Any(IsNull));
+    uint32_t index = 0;
     for (auto* param : params_) {
         param->SetFunction(this);
+        param->SetIndex(index++);
     }
 }
 
@@ -82,14 +84,17 @@
     }
     params_ = params;
     TINT_ASSERT(!params_.Any(IsNull));
+    uint32_t index = 0;
     for (auto* param : params_) {
         param->SetFunction(this);
+        param->SetIndex(index++);
     }
 }
 
 void Function::AppendParam(FunctionParam* param) {
     params_.Push(param);
     param->SetFunction(this);
+    param->SetIndex(static_cast<uint32_t>(params_.Length() - 1u));
 }
 
 void Function::Destroy() {
diff --git a/src/tint/lang/core/ir/function_param.h b/src/tint/lang/core/ir/function_param.h
index 14d8f92..c9a0cea 100644
--- a/src/tint/lang/core/ir/function_param.h
+++ b/src/tint/lang/core/ir/function_param.h
@@ -63,6 +63,13 @@
     /// @returns the function that this parameter belongs to, or nullptr
     const ir::Function* Function() const { return func_; }
 
+    /// Sets the index of the parameter in the function's parameter list
+    /// @param index the index
+    void SetIndex(uint32_t index) { index_ = index; }
+
+    /// @returns the index of the parameter in the function's parameter list
+    uint32_t Index() const { return index_; }
+
     /// @returns the type of the var
     const core::type::Type* Type() const override { return type_; }
 
@@ -121,6 +128,7 @@
 
   private:
     ir::Function* func_ = nullptr;
+    uint32_t index_ = 0xffffffff;
     const core::type::Type* type_ = nullptr;
     std::optional<core::BuiltinValue> builtin_;
     std::optional<struct Location> location_;
diff --git a/src/tint/lang/core/ir/function_test.cc b/src/tint/lang/core/ir/function_test.cc
index 9f0161a..eda7fdd 100644
--- a/src/tint/lang/core/ir/function_test.cc
+++ b/src/tint/lang/core/ir/function_test.cc
@@ -154,16 +154,23 @@
     EXPECT_EQ(param1->Function(), f);
     EXPECT_EQ(param2->Function(), f);
     EXPECT_EQ(param3->Function(), nullptr);
+    EXPECT_EQ(param1->Index(), 0u);
+    EXPECT_EQ(param2->Index(), 1u);
 
     f->SetParams({param1, param3});
     EXPECT_EQ(param1->Function(), f);
     EXPECT_EQ(param2->Function(), nullptr);
     EXPECT_EQ(param3->Function(), f);
+    EXPECT_EQ(param1->Index(), 0u);
+    EXPECT_EQ(param3->Index(), 1u);
 
     f->AppendParam(param2);
     EXPECT_EQ(param1->Function(), f);
     EXPECT_EQ(param2->Function(), f);
     EXPECT_EQ(param3->Function(), f);
+    EXPECT_EQ(param1->Index(), 0u);
+    EXPECT_EQ(param3->Index(), 1u);
+    EXPECT_EQ(param2->Index(), 2u);
 }
 
 }  // namespace