From 268f6bfc1d383efe6793907c9d26209df2e96c94 Mon Sep 17 00:00:00 2001
From: Trevor Elliott <telliott@fastly.com>
Date: Tue, 31 Jan 2023 18:53:23 -0800
Subject: [PATCH] Revert "Cranelift: Rewrite `or(and(x, y), not(y)) => or(x,
 not(y))` (#5676)" (#5682)

This reverts commit 8c9eb9939bfbe634aa80097b02f34068549e804b.

Fixes #5680
---
 cranelift/codegen/src/isle_prelude.rs         |  5 ---
 cranelift/codegen/src/opts/algebraic.isle     | 27 ------------
 cranelift/codegen/src/prelude.isle            |  3 --
 .../filetests/filetests/egraph/algebraic.clif | 44 +------------------
 .../runtests/or-and-y-with-not-y.clif         | 34 --------------
 5 files changed, 1 insertion(+), 112 deletions(-)
 delete mode 100644 cranelift/filetests/filetests/runtests/or-and-y-with-not-y.clif

diff --git a/cranelift/codegen/src/isle_prelude.rs b/cranelift/codegen/src/isle_prelude.rs
index 3d5a7f3bdb..a32cee62c0 100644
--- a/cranelift/codegen/src/isle_prelude.rs
+++ b/cranelift/codegen/src/isle_prelude.rs
@@ -109,11 +109,6 @@ macro_rules! isle_common_prelude_methods {
             !x
         }
 
-        #[inline]
-        fn u64_eq(&mut self, x: u64, y: u64) -> u64 {
-            u64::from(x == y)
-        }
-
         #[inline]
         fn u64_is_zero(&mut self, value: u64) -> bool {
             0 == value
diff --git a/cranelift/codegen/src/opts/algebraic.isle b/cranelift/codegen/src/opts/algebraic.isle
index 1369cbfab0..64a64a3a1f 100644
--- a/cranelift/codegen/src/opts/algebraic.isle
+++ b/cranelift/codegen/src/opts/algebraic.isle
@@ -138,33 +138,6 @@
 (rule (simplify (bnot ty (band t x y)))
       (bor ty (bnot ty x) (bnot ty y)))
 
-;; `or(and(x, y), not(y)) == or(x, not(y))`
-(rule (simplify (bor ty
-                     (band ty x y)
-                     z @ (bnot ty y)))
-      (bor ty x z))
-;; Duplicate the rule but swap the `bor` operands because `bor` is
-;; commutative. We could, of course, add a `simplify` rule to do the commutative
-;; swap for all `bor`s but this will bloat the e-graph with many e-nodes. It is
-;; cheaper to have additional rules, rather than additional e-nodes, because we
-;; amortize their cost via ISLE's smart codegen.
-(rule (simplify (bor ty
-                     z @ (bnot ty y)
-                     (band ty x y)))
-      (bor ty x z))
-
-;; `or(and(x, y), not(y)) == or(x, not(y))` specialized for constants, since
-;; otherwise we may not know that `z == not(y)` since we don't generally expand
-;; constants in the e-graph.
-;;
-;; (No need to duplicate for commutative `bor` for this constant version because
-;; we move constants to the right.)
-(rule (simplify (bor ty
-                     (band ty x (iconst ty (u64_from_imm64 y)))
-                     z @ (iconst ty (u64_from_imm64 zk))))
-      (if (u64_eq zk (u64_not y)))
-      (bor ty x z))
-
 ;; x*2 == 2*x == x+x.
 (rule (simplify (imul ty x (iconst _ (simm32 2))))
       (iadd ty x x))
diff --git a/cranelift/codegen/src/prelude.isle b/cranelift/codegen/src/prelude.isle
index fea0eee2f9..c1e7c8d2b8 100644
--- a/cranelift/codegen/src/prelude.isle
+++ b/cranelift/codegen/src/prelude.isle
@@ -141,9 +141,6 @@
 (decl pure u64_not (u64) u64)
 (extern constructor u64_not u64_not)
 
-(decl pure u64_eq (u64 u64) u64)
-(extern constructor u64_eq u64_eq)
-
 (decl pure u64_sextend_u32 (u64) u64)
 (extern constructor u64_sextend_u32 u64_sextend_u32)
 
diff --git a/cranelift/filetests/filetests/egraph/algebraic.clif b/cranelift/filetests/filetests/egraph/algebraic.clif
index 54a786b466..33e83936c7 100644
--- a/cranelift/filetests/filetests/egraph/algebraic.clif
+++ b/cranelift/filetests/filetests/egraph/algebraic.clif
@@ -40,7 +40,7 @@ block0(v0: i32):
     return v3
     ; check: v4 = iconst.i32 0xffff_ffe0
     ; check: v5 = band v0, v4
-    ; check: return v5
+    ; return v5
 }
 
 function %unsigned_shift_right_shift_left_i64(i64) -> i64 {
@@ -86,45 +86,3 @@ block0(v0: i64):
     ; check: v5 = band v0, v4
     ; return v5
 }
-
-function %or_and_y_with_not_y(i8, i8) -> i8 {
-block0(v0: i8, v1: i8):
-    v2 = band v0, v1
-    v3 = bnot v1
-    v4 = bor v2, v3
-    return v4
-    ; check: v5 = bor v0, v3
-    ; check: return v5
-}
-
-function %or_and_constant_with_not_constant(i8) -> i8 {
-block0(v0: i8):
-    v1 = iconst.i8 -4
-    v2 = band v0, v1
-    v3 = iconst.i8 3
-    v4 = bor v2, v3
-    return v4
-    ; check: v5 = bor v0, v3
-    ; check: return v5
-}
-
-function %or_and_y_with_not_y(i8, i8) -> i8 {
-block0(v0: i8, v1: i8):
-    v2 = band v0, v1
-    v3 = bnot v1
-    v4 = bor v3, v2
-    return v4
-    ; check: v5 = bor v0, v3
-    ; check: return v5
-}
-
-function %or_and_constant_with_not_constant(i8) -> i8 {
-block0(v0: i8):
-    v1 = iconst.i8 -4
-    v2 = band v0, v1
-    v3 = iconst.i8 3
-    v4 = bor v3, v2
-    return v4
-    ; check: v6 = bor v0, v3
-    ; check: return v6
-}
diff --git a/cranelift/filetests/filetests/runtests/or-and-y-with-not-y.clif b/cranelift/filetests/filetests/runtests/or-and-y-with-not-y.clif
deleted file mode 100644
index 55532d23bc..0000000000
--- a/cranelift/filetests/filetests/runtests/or-and-y-with-not-y.clif
+++ /dev/null
@@ -1,34 +0,0 @@
-;; Test the rewrite: `or(and(x, y), not(y)) => or(x, not(y))`
-
-test interpret
-test run
-target aarch64
-target x86_64
-target riscv64
-target s390x
-
-function %or_and_y_with_not_y(i8, i8) -> i8 {
-block0(v0: i8, v1: i8):
-    v2 = band v0, v1
-    v3 = bnot v1
-    v4 = bor v2, v3
-    return v4
-}
-; run: %or_and_y_with_not_y(0xff, 0x0a) == 0xff
-; run: %or_and_y_with_not_y(0xff, 0xb0) == 0xff
-; run: %or_and_y_with_not_y(0xaa, 0x0a) == 0xff
-; run: %or_and_y_with_not_y(0xaa, 0xb0) == 0xef
-; run: %or_and_y_with_not_y(0x00, 0x0a) == 0xf5
-; run: %or_and_y_with_not_y(0x00, 0xb0) == 0x4f
-
-function %or_and_constant_with_not_constant(i8) -> i8 {
-block0(v0: i8):
-    v1 = iconst.i8 -4
-    v2 = band v0, v1
-    v3 = iconst.i8 3
-    v4 = bor v2, v3
-    return v4
-}
-; run: %or_and_constant_with_not_constant(0xff) == 0xff
-; run: %or_and_constant_with_not_constant(0xaa) == 0xab
-; run: %or_and_constant_with_not_constant(0x00) == 0x03