From 8b85a07f977f374d8d76831c1cb9c93796772094 Mon Sep 17 00:00:00 2001
From: Kartik Agaram <vc@akkartik.com>
Date: Thu, 27 Feb 2020 16:58:16 -0800
Subject: [PATCH] 6059

---
 mu_instructions | 8 ++++++++
 mu_summary      | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/mu_instructions b/mu_instructions
index 017527b9..941401dc 100644
--- a/mu_instructions
+++ b/mu_instructions
@@ -215,4 +215,12 @@ var/reg <- index arr/rega: (addr array T), n
 compare var, n              {.name="compare",         .inouts=[var, n],                 .subx-name="81 7/subop/compare",    .rm32="*(ebp+" inouts[0].stack-offset ")",                      .imm32=inouts[1]}
                             {.name="index",           .inouts=[rega, n], .outputs=[reg], .subx-name="8d/copy-address",      .rm32="*(" inouts[0] "+" inouts[1] "<<2)",  .r32=outputs[0]}
 
+User-defined types
+
+If a record (product) type T was defined to have elements a, b, c, ... of
+types T_a, T_b, T_c, ..., then accessing one of those elements f of type T_f:
+
+var/reg: (addr T_f) <- get var2/reg2: (addr F), f: field name => 8d/copy-addr *(reg2+offset(f))
+                            {.name="get",             .inouts=[reg2, f],                .subx-name="8d/copy-addr",          .rm32="*(" inouts[0] "+" offset(f) ")",     .r32=outputs[0]}
+
 vim:ft=c:nowrap
diff --git a/mu_summary b/mu_summary
index 3a93d109..179aa11f 100644
--- a/mu_summary
+++ b/mu_summary
@@ -200,3 +200,8 @@ Similarly, conditional loops:
   var/reg: int <- length var: (addr array T)
   var/reg: (addr T) <- index var: (addr array T), idx: int
   var/reg: (addr T) <- index var: (addr array T), n
+
+## User-defined types
+
+  var/reg: (addr T_f) <- get var: (addr T), f
+    where record (product) type T has elements a, b, c, ... of types T_a, T_b, T_c, ...