From c760292a7c1aa31b203686442fca8501cb3e0dce Mon Sep 17 00:00:00 2001
From: Chris Dodd <cdodd@acm.org>
Date: Thu, 30 Jan 2025 14:52:47 +1300
Subject: [PATCH] Add op= assignments

Signed-off-by: Chris Dodd <cdodd@acm.org>
---
 p4-16/spec/P4-16-spec.adoc |  6 ++++++
 p4-16/spec/grammar.adoc    | 14 +++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/p4-16/spec/P4-16-spec.adoc b/p4-16/spec/P4-16-spec.adoc
index d6a5d4d43c..625ebe66f5 100644
--- a/p4-16/spec/P4-16-spec.adoc
+++ b/p4-16/spec/P4-16-spec.adoc
@@ -5498,6 +5498,12 @@ types (e.g. ``struct``s) are copied recursively, and all components
 of ``header``s are copied, including "validity" bits. Assignment is
 not defined for `extern` values.
 
+An assignment may also be written with a binary operator immediately
+before the `=` sign.  This performs the binary operator on the old
+value of the left sub-expression and the right sub-expression and assigns
+the result to the l-value.  Thus an assignment like `A += B` is equivalent
+to `A = A + B`, except that `A` is only evaluated once.
+
 [#sec-empty-stmt]
 === Empty statement
 
diff --git a/p4-16/spec/grammar.adoc b/p4-16/spec/grammar.adoc
index d857ef7645..ff868b07d9 100644
--- a/p4-16/spec/grammar.adoc
+++ b/p4-16/spec/grammar.adoc
@@ -736,7 +736,19 @@ typedefDeclaration
 assignmentOrMethodCallStatement
     : lvalue "(" argumentList ")" ";"
     | lvalue "<" typeArgumentList ">" "(" argumentList ")" ";"
-    | lvalue "="  expression ";"
+    | lvalue "=" expression ";"
+    | lvalue "*=" expression ";"
+    | lvalue "/=" expression ";"
+    | lvalue "%=" expression ";"
+    | lvalue "+=" expression ";"
+    | lvalue "-=" expression ";"
+    | lvalue "|+|=" expression ";"
+    | lvalue "|-|=" expression ";"
+    | lvalue "<<=" expression ";"
+    | lvalue ">>=" expression ";"
+    | lvalue "&=" expression ";"
+    | lvalue "|=" expression ";"
+    | lvalue "^=" expression ";"
     ;
 // end::assignmentOrMethodCallStatement[]