From 6df3bbbe606109b7ccaba1e12fcc35b2a248fa2a Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Mon, 13 Feb 2023 14:43:17 -0800
Subject: [PATCH] Cranelift: Collapse double extends into a single extend
 (#5772)

---
 cranelift/codegen/src/opts/algebraic.isle     |  6 ++++++
 .../filetests/filetests/egraph/algebraic.clif | 20 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/cranelift/codegen/src/opts/algebraic.isle b/cranelift/codegen/src/opts/algebraic.isle
index e227a40896..8193f7945e 100644
--- a/cranelift/codegen/src/opts/algebraic.isle
+++ b/cranelift/codegen/src/opts/algebraic.isle
@@ -6,6 +6,12 @@
 ;; than a piece of the input or a new node that we construct; but we
 ;; can freely rewrite e.g. `x+y-y` to `x`.
 
+;; Chained `uextend` and `sextend`.
+(rule (simplify (uextend ty (uextend _intermediate_ty x)))
+      (uextend ty x))
+(rule (simplify (sextend ty (sextend _intermediate_ty x)))
+      (sextend ty x))
+
 ;; x+0 == 0+x == x.
 (rule (simplify (iadd ty
                       x
diff --git a/cranelift/filetests/filetests/egraph/algebraic.clif b/cranelift/filetests/filetests/egraph/algebraic.clif
index af8062d6ad..3e8577cdbe 100644
--- a/cranelift/filetests/filetests/egraph/algebraic.clif
+++ b/cranelift/filetests/filetests/egraph/algebraic.clif
@@ -337,3 +337,23 @@ block0(v1: i32):
 
 ; check: v5 = iconst.i8 1
 ; check: return v5
+
+function %double_uextend(i16) -> i64 {
+block0(v1: i16):
+    v2 = uextend.i32 v1
+    v3 = uextend.i64 v2
+    return v3
+}
+
+; check: v4 = uextend.i64 v1
+; check: return v4
+
+function %double_sextend(i16) -> i64 {
+block0(v1: i16):
+    v2 = sextend.i32 v1
+    v3 = sextend.i64 v2
+    return v3
+}
+
+; check: v4 = sextend.i64 v1
+; check: return v4