From 30d957cccababe731cb55fde4e03e5b6f09c95bf Mon Sep 17 00:00:00 2001
From: Laurence Tratt <laurie@tratt.net>
Date: Thu, 27 Feb 2025 09:54:34 +0000
Subject: [PATCH] Optimise `PtrAdd`s that were optimised from `DynPtrAdd`.

In essence, when we've been able to convert a `DynPtrAdd` to a `PtrAdd`,
we can then run our existing `PtrAdd` optimisation on the result. This
can then show up further optimisation opportunities to CSE.
---
 ykrt/src/compile/jitc_yk/opt/mod.rs | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/ykrt/src/compile/jitc_yk/opt/mod.rs b/ykrt/src/compile/jitc_yk/opt/mod.rs
index 22e0a5d34..e2994e20a 100644
--- a/ykrt/src/compile/jitc_yk/opt/mod.rs
+++ b/ykrt/src/compile/jitc_yk/opt/mod.rs
@@ -580,8 +580,9 @@ impl Opt {
                     Operand::Const(cidx) => self.m.replace(iidx, Inst::Const(cidx)),
                 }
             } else {
-                self.m
-                    .replace(iidx, Inst::PtrAdd(PtrAddInst::new(inst.ptr(&self.m), off)));
+                let pa_inst = PtrAddInst::new(inst.ptr(&self.m), off);
+                self.m.replace(iidx, Inst::PtrAdd(pa_inst.clone()));
+                self.opt_ptradd(iidx, pa_inst)?;
             }
         }
 
@@ -1776,7 +1777,7 @@ mod test {
     }
 
     #[test]
-    fn opt_dynptradd_const() {
+    fn opt_dynptradd() {
         Module::assert_ir_transform_eq(
             "
           entry:
@@ -1807,6 +1808,23 @@ mod test {
             black_box 0x1234
         ",
         );
+
+        Module::assert_ir_transform_eq(
+            "
+          entry:
+            %0: ptr = param reg
+            %1: ptr = ptr_add %0, -4
+            %2: ptr = dyn_ptr_add %1, 1i64, 4
+            black_box %2
+        ",
+            |m| opt(m).unwrap(),
+            "
+          ...
+          entry:
+            %0: ptr = param ...
+            black_box %0
+        ",
+        );
     }
 
     #[test]