[compiler] Add a simplifier rule to replace match with is (#18070)

If looking at `match (e) { V => true, _ => false }`, we reduce this to `e is V`, which is more efficient.

Author: wrwg

third_party/move/move-compiler-v2/src/env_pipeline/ast_simplifier.rs

@@ -52,7 +52,7 @@ use itertools::Itertools;
 use log::{debug, log_enabled, trace, Level};
 use move_core_types::ability::Ability;
 use move_model::{
-    ast::{Exp, ExpData, Operation, Pattern, Value, VisitorPosition},
+    ast::{Exp, ExpData, MatchArm, Operation, Pattern, Value, VisitorPosition},
     constant_folder::ConstantFolder,
     exp_rewriter::ExpRewriterFunctions,
     model::{FunctionEnv, GlobalEnv, NodeId, Parameter},
@@ -870,6 +870,41 @@ impl ExpRewriterFunctions for SimplifierRewriter<'_> {
             })
     }
 
+    fn rewrite_match(&mut self, id: NodeId, disc: &Exp, arms: &[MatchArm]) -> Option<Exp> {
+        // match (e) { V(_) => true, _ => false } ==> e is V
+        let is_bool = |e: &Exp, test: bool| -> bool {
+            matches!(e.as_ref(), ExpData::Value(_, Value::Bool(v)) if test == *v)
+        };
+        if arms.len() == 2
+            && let MatchArm {
+                loc: _,
+                pattern: Pattern::Struct(_, qid, Some(variant), args),
+                condition: None,
+                body,
+            } = &arms[0]
+            && args.iter().all(|p| matches!(p, Pattern::Wildcard(_)))
+            && is_bool(body, true)
+            && let MatchArm {
+                loc: _,
+                pattern: Pattern::Wildcard(_),
+                condition: None,
+                body,
+            } = &arms[1]
+            && is_bool(body, false)
+        {
+            Some(
+                ExpData::Call(
+                    id,
+                    Operation::TestVariants(qid.module_id, qid.id, vec![*variant]),
+                    vec![disc.clone()],
+                )
+                .into_exp(),
+            )
+        } else {
+            None
+        }
+    }
+
     fn rewrite_enter_block_scope(
         &mut self,
         id: NodeId,

third_party/move/move-compiler-v2/tests/file-format-generator/struct_variants.exp

@@ -87,29 +87,8 @@ l1: move_loc l2
 
 // Function definition at index 1
 #[persistent] public fun is_inner1(l0: &Inner): bool
-    local l1: bool
-    local l2: &Inner
-    copy_loc l0
-    test_variant Inner, Inner1
-    br_false l0
     move_loc l0
-    pop
-    // @5
-    ld_true
-    st_loc l1
-    branch l1
-l0: move_loc l0
-    st_loc l2
-    // @10
-    move_loc l2
-    pop
-    ld_false
-    st_loc l1
-    branch l1
-    // @15
-    ld_u64 14566554180833181697
-    abort
-l1: move_loc l1
+    test_variant Inner, Inner1
     ret
 
 // Function definition at index 2

third_party/move/move-compiler-v2/tests/file-format-generator/struct_variants.opt.exp

@@ -76,18 +76,8 @@ l1: ld_u64 14566554180833181697
 
 // Function definition at index 1
 #[persistent] public fun is_inner1(l0: &Inner): bool
-    copy_loc l0
-    test_variant Inner, Inner1
-    br_false l0
     move_loc l0
-    pop
-    // @5
-    ld_true
-    ret
-l0: move_loc l0
-    pop
-    ld_false
-    // @10
+    test_variant Inner, Inner1
     ret
 
 // Function definition at index 2

third_party/move/move-compiler-v2/tests/file-format-generator/variants_match_reduces_to_is.exp

@@ -12,29 +12,8 @@ enum Color
 
 // Function definition at index 0
 fun test_red(l0: &Color): bool
-    local l1: bool
-    local l2: &Color
-    copy_loc l0
-    test_variant Color, Red
-    br_false l0
     move_loc l0
-    pop
-    // @5
-    ld_true
-    st_loc l1
-    branch l1
-l0: move_loc l0
-    st_loc l2
-    // @10
-    move_loc l2
-    pop
-    ld_false
-    st_loc l1
-    branch l1
-    // @15
-    ld_u64 14566554180833181697
-    abort
-l1: move_loc l1
+    test_variant Color, Red
     ret
 
 // Function definition at index 1

third_party/move/move-compiler-v2/tests/file-format-generator/variants_match_reduces_to_is.opt.exp

@@ -12,18 +12,8 @@ enum Color
 
 // Function definition at index 0
 fun test_red(l0: &Color): bool
-    copy_loc l0
-    test_variant Color, Red
-    br_false l0
     move_loc l0
-    pop
-    // @5
-    ld_true
-    ret
-l0: move_loc l0
-    pop
-    ld_false
-    // @10
+    test_variant Color, Red
     ret
 
 // Function definition at index 1

third_party/move/move-compiler-v2/tests/simplifier/match.exp

@@ -0,0 +1,61 @@
+// -- Model dump before first bytecode pipeline
+module 0x66::m {
+    enum E {
+        A {
+            0: u64,
+        }
+        B,
+        C {
+            0: bool,
+        }
+    }
+    private fun variant_test(e: &E): bool {
+        match (e) {
+          m::E::A{ 0: _ } => {
+            true
+          }
+          _: &E => {
+            false
+          }
+        }
+
+    }
+} // end 0x66::m
+
+// -- Sourcified model before first bytecode pipeline
+module 0x66::m {
+    enum E {
+        A {
+            0: u64,
+        }
+        B,
+        C {
+            0: bool,
+        }
+    }
+    fun variant_test(e: &E): bool {
+        match (e) {
+            E::A(_) => true,
+            _ => false,
+        }
+    }
+}
+
+// -- Model dump before second bytecode pipeline
+module 0x66::m {
+    enum E {
+        A {
+            0: u64,
+        }
+        B,
+        C {
+            0: bool,
+        }
+    }
+    private fun variant_test(e: &E): bool {
+        test_variants m::E::A(e)
+    }
+} // end 0x66::m
+
+
+============ bytecode verification succeeded ========

third_party/move/move-compiler-v2/tests/simplifier/match.move

@@ -0,0 +1,15 @@
+module 0x66::m {
+
+    enum E {
+        A(u64),
+        B,
+        C(bool)
+    }
+
+    fun variant_test(e: &E): bool {
+        match (e) {
+            A(_) => true,
+            _ => false
+        }
+    }
+}

third_party/move/move-compiler-v2/transactional-tests/tests/no-v1-comparison/enum/round-trip/enum_matching.decompiled

@@ -54,8 +54,7 @@ module 0x42::m {
         _v2 + _v3
     }
     public fun is_inner1(p0: &Inner): bool {
-        if (p0 is Inner1) return true;
-        false
+        p0 is Inner1
     }
     public fun is_some<T0>(p0: &Option<T0>): bool {
         loop {

third_party/move/move-compiler-v2/transactional-tests/tests/no-v1-comparison/enum/round-trip/enum_matching.decompiled.baseline.exp

@@ -1,30 +1,30 @@
 processed 15 tasks
-task 0 lines 3-257:  publish [module 0x42::m {]
-task 1 lines 260-260:  run 0x42::m::t1_is_inner1
+task 0 lines 3-256:  publish [module 0x42::m {]
+task 1 lines 259-259:  run 0x42::m::t1_is_inner1
 return values: true
-task 2 lines 262-262:  run 0x42::m::t2_is_inner1
+task 2 lines 261-261:  run 0x42::m::t2_is_inner1
 return values: false
-task 3 lines 264-264:  run 0x42::m::t1_inner_value
+task 3 lines 263-263:  run 0x42::m::t1_inner_value
 return values: 7
-task 4 lines 266-266:  run 0x42::m::t1_outer_value
+task 4 lines 265-265:  run 0x42::m::t1_outer_value
 return values: 0
-task 5 lines 268-268:  run 0x42::m::t2_outer_value
+task 5 lines 267-267:  run 0x42::m::t2_outer_value
 return values: 3
-task 6 lines 270-270:  run 0x42::m::t3_outer_value
+task 6 lines 269-269:  run 0x42::m::t3_outer_value
 return values: 8
-task 7 lines 272-272:  run 0x42::m::t1_outer_value_nested
+task 7 lines 271-271:  run 0x42::m::t1_outer_value_nested
 return values: 27
-task 8 lines 274-274:  run 0x42::m::t2_outer_value_nested
+task 8 lines 273-273:  run 0x42::m::t2_outer_value_nested
 return values: 12
-task 9 lines 276-276:  run 0x42::m::t1_outer_value_with_cond
+task 9 lines 275-275:  run 0x42::m::t1_outer_value_with_cond
 return values: 1
-task 10 lines 278-278:  run 0x42::m::t1_outer_value_with_cond_ref
+task 10 lines 277-277:  run 0x42::m::t1_outer_value_with_cond_ref
 return values: true
-task 11 lines 280-280:  run 0x42::m::t1_is_some
+task 11 lines 279-279:  run 0x42::m::t1_is_some
 return values: false
-task 12 lines 282-282:  run 0x42::m::t2_is_some
+task 12 lines 281-281:  run 0x42::m::t2_is_some
 return values: true
-task 13 lines 284-284:  run 0x42::m::t1_is_some_specialized
+task 13 lines 283-283:  run 0x42::m::t1_is_some_specialized
 return values: false
-task 14 lines 286-286:  run 0x42::m::t2_is_some_specialized
+task 14 lines 285-285:  run 0x42::m::t2_is_some_specialized
 return values: true

third_party/move/move-compiler-v2/transactional-tests/tests/no-v1-comparison/enum/round-trip/enum_scoping.decompiled

@@ -25,7 +25,6 @@ module 0x42::m {
         }
     }
     public fun check_scoping(p0: &Inner): u64 {
-        if (p0 is Inner1) ();
         3
     }
     fun t1_check_scoping(): u64 {