Auto merge of #105356 - JakobDegen:more-custom-mir, r=oli-obk

Custom MIR: Many more improvements

Commits are each atomic changes, best reviewed one at a time, with the exception that the last commit includes all the documentation.

### First commit

Unsafetyck was not correctly disabled before for `dialect = "built"` custom MIR. This is fixed and a regression test is added.

### Second commit

Implements `Discriminant`, `SetDiscriminant`, and `SwitchInt`.

### Third commit

Implements indexing, field, and variant projections.

### Fourth commit

Documents the previous commits and everything else.

There is some amount of weirdness here due to having to beat Rust syntax into cooperating with MIR concepts, but it hopefully should not be too much. All of it is documented.

r? `@oli-obk`

15 files changed, 376 insertions, 0 deletions

diff --git a/src/test/mir-opt/building/custom/enums.rs b/src/test/mir-opt/building/custom/enums.rs
new file mode 100644
index 00000000000..e5cd4563778
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.rs
@@ -0,0 +1,120 @@
+#![feature(custom_mir, core_intrinsics)]
+
+extern crate core;
+use core::intrinsics::mir::*;
+
+// EMIT_MIR enums.switch_bool.built.after.mir
+#[custom_mir(dialect = "built")]
+pub fn switch_bool(b: bool) -> u32 {
+    mir!(
+        {
+            match b {
+                true => t,
+                false => f,
+                _ => f,
+            }
+        }
+
+        t = {
+            RET = 5;
+            Return()
+        }
+
+        f = {
+            RET = 10;
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR enums.switch_option.built.after.mir
+#[custom_mir(dialect = "built")]
+pub fn switch_option(option: Option<()>) -> bool {
+    mir!(
+        {
+            let discr = Discriminant(option);
+            match discr {
+                0 => n,
+                1 => s,
+                _ => s,
+            }
+        }
+
+        n = {
+            RET = false;
+            Return()
+        }
+
+        s = {
+            RET = true;
+            Return()
+        }
+    )
+}
+
+#[repr(u8)]
+enum Bool {
+    False = 0,
+    True = 1,
+}
+
+// EMIT_MIR enums.switch_option_repr.built.after.mir
+#[custom_mir(dialect = "built")]
+fn switch_option_repr(option: Bool) -> bool {
+    mir!(
+        {
+            let discr = Discriminant(option);
+            match discr {
+                0 => f,
+                _ => t,
+            }
+        }
+
+        t = {
+            RET = true;
+            Return()
+        }
+
+        f = {
+            RET = false;
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR enums.set_discr.built.after.mir
+#[custom_mir(dialect = "runtime", phase = "initial")]
+fn set_discr(option: &mut Option<()>) {
+    mir!({
+        SetDiscriminant(*option, 0);
+        Return()
+    })
+}
+
+// EMIT_MIR enums.set_discr_repr.built.after.mir
+#[custom_mir(dialect = "runtime", phase = "initial")]
+fn set_discr_repr(b: &mut Bool) {
+    mir!({
+        SetDiscriminant(*b, 0);
+        Return()
+    })
+}
+
+fn main() {
+    assert_eq!(switch_bool(true), 5);
+    assert_eq!(switch_bool(false), 10);
+
+    assert_eq!(switch_option(Some(())), true);
+    assert_eq!(switch_option(None), false);
+
+    assert_eq!(switch_option_repr(Bool::True), true);
+    assert_eq!(switch_option_repr(Bool::False), false);
+
+    let mut opt = Some(());
+    set_discr(&mut opt);
+    assert_eq!(opt, None);
+
+    let mut b = Bool::True;
+    set_discr_repr(&mut b);
+    assert!(matches!(b, Bool::False));
+}
diff --git a/src/test/mir-opt/building/custom/enums.set_discr.built.after.mir b/src/test/mir-opt/building/custom/enums.set_discr.built.after.mir
new file mode 100644
index 00000000000..7de9ed0983f
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.set_discr.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `set_discr` after built
+
+fn set_discr(_1: &mut Option<()>) -> () {
+    let mut _0: ();                      // return place in scope 0 at $DIR/enums.rs:+0:39: +0:39
+
+    bb0: {
+        discriminant((*_1)) = 0;         // scope 0 at $DIR/enums.rs:+2:9: +2:36
+        return;                          // scope 0 at $DIR/enums.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/enums.set_discr_repr.built.after.mir b/src/test/mir-opt/building/custom/enums.set_discr_repr.built.after.mir
new file mode 100644
index 00000000000..6fdc3d0f4d4
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.set_discr_repr.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `set_discr_repr` after built
+
+fn set_discr_repr(_1: &mut Bool) -> () {
+    let mut _0: ();                      // return place in scope 0 at $DIR/enums.rs:+0:33: +0:33
+
+    bb0: {
+        discriminant((*_1)) = 0;         // scope 0 at $DIR/enums.rs:+2:9: +2:31
+        return;                          // scope 0 at $DIR/enums.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/enums.switch_bool.built.after.mir b/src/test/mir-opt/building/custom/enums.switch_bool.built.after.mir
new file mode 100644
index 00000000000..95c57d2dca3
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.switch_bool.built.after.mir
@@ -0,0 +1,19 @@
+// MIR for `switch_bool` after built
+
+fn switch_bool(_1: bool) -> u32 {
+    let mut _0: u32;                     // return place in scope 0 at $DIR/enums.rs:+0:32: +0:35
+
+    bb0: {
+        switchInt(_1) -> [1: bb1, 0: bb2, otherwise: bb2]; // scope 0 at $DIR/enums.rs:+3:13: +7:14
+    }
+
+    bb1: {
+        _0 = const 5_u32;                // scope 0 at $DIR/enums.rs:+11:13: +11:20
+        return;                          // scope 0 at $DIR/enums.rs:+12:13: +12:21
+    }
+
+    bb2: {
+        _0 = const 10_u32;               // scope 0 at $DIR/enums.rs:+16:13: +16:21
+        return;                          // scope 0 at $DIR/enums.rs:+17:13: +17:21
+    }
+}
diff --git a/src/test/mir-opt/building/custom/enums.switch_option.built.after.mir b/src/test/mir-opt/building/custom/enums.switch_option.built.after.mir
new file mode 100644
index 00000000000..a659ba7c114
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.switch_option.built.after.mir
@@ -0,0 +1,21 @@
+// MIR for `switch_option` after built
+
+fn switch_option(_1: Option<()>) -> bool {
+    let mut _0: bool;                    // return place in scope 0 at $DIR/enums.rs:+0:45: +0:49
+    let mut _2: isize;                   // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        _2 = discriminant(_1);           // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+        switchInt(_2) -> [0: bb1, 1: bb2, otherwise: bb2]; // scope 0 at $DIR/enums.rs:+4:13: +8:14
+    }
+
+    bb1: {
+        _0 = const false;                // scope 0 at $DIR/enums.rs:+12:13: +12:24
+        return;                          // scope 0 at $DIR/enums.rs:+13:13: +13:21
+    }
+
+    bb2: {
+        _0 = const true;                 // scope 0 at $DIR/enums.rs:+17:13: +17:23
+        return;                          // scope 0 at $DIR/enums.rs:+18:13: +18:21
+    }
+}
diff --git a/src/test/mir-opt/building/custom/enums.switch_option_repr.built.after.mir b/src/test/mir-opt/building/custom/enums.switch_option_repr.built.after.mir
new file mode 100644
index 00000000000..d60e4b1b712
--- /dev/null
+++ b/src/test/mir-opt/building/custom/enums.switch_option_repr.built.after.mir
@@ -0,0 +1,21 @@
+// MIR for `switch_option_repr` after built
+
+fn switch_option_repr(_1: Bool) -> bool {
+    let mut _0: bool;                    // return place in scope 0 at $DIR/enums.rs:+0:40: +0:44
+    let mut _2: u8;                      // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        _2 = discriminant(_1);           // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+        switchInt(_2) -> [0: bb2, otherwise: bb1]; // scope 0 at $DIR/enums.rs:+4:13: +7:14
+    }
+
+    bb1: {
+        _0 = const true;                 // scope 0 at $DIR/enums.rs:+11:13: +11:23
+        return;                          // scope 0 at $DIR/enums.rs:+12:13: +12:21
+    }
+
+    bb2: {
+        _0 = const false;                // scope 0 at $DIR/enums.rs:+16:13: +16:24
+        return;                          // scope 0 at $DIR/enums.rs:+17:13: +17:21
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.rs b/src/test/mir-opt/building/custom/projections.rs
new file mode 100644
index 00000000000..5e472e531c7
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.rs
@@ -0,0 +1,85 @@
+#![feature(custom_mir, core_intrinsics)]
+
+extern crate core;
+use core::intrinsics::mir::*;
+
+union U {
+    a: i32,
+    b: u32,
+}
+
+// EMIT_MIR projections.unions.built.after.mir
+#[custom_mir(dialect = "built")]
+fn unions(u: U) -> i32 {
+    mir!({
+        RET = u.a;
+        Return()
+    })
+}
+
+// EMIT_MIR projections.tuples.built.after.mir
+#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
+fn tuples(i: (u32, i32)) -> (u32, i32) {
+    mir!(
+        // FIXME(JakobDegen): This is necessary because we can't give type hints for `RET`
+        let temp: (u32, i32);
+        {
+            temp.0 = i.0;
+            temp.1 = i.1;
+
+            RET = temp;
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR projections.unwrap.built.after.mir
+#[custom_mir(dialect = "built")]
+fn unwrap(opt: Option<i32>) -> i32 {
+    mir!({
+        RET = Field(Variant(opt, 1), 0);
+        Return()
+    })
+}
+
+// EMIT_MIR projections.unwrap_deref.built.after.mir
+#[custom_mir(dialect = "built")]
+fn unwrap_deref(opt: Option<&i32>) -> i32 {
+    mir!({
+        RET = *Field::<&i32>(Variant(opt, 1), 0);
+        Return()
+    })
+}
+
+// EMIT_MIR projections.set.built.after.mir
+#[custom_mir(dialect = "built")]
+fn set(opt: &mut Option<i32>) {
+    mir!({
+        place!(Field(Variant(*opt, 1), 0)) = 10;
+        Return()
+    })
+}
+
+// EMIT_MIR projections.simple_index.built.after.mir
+#[custom_mir(dialect = "built")]
+fn simple_index(a: [i32; 10], b: &[i32]) -> i32 {
+    mir!({
+        let temp = 3;
+        RET = a[temp];
+        RET = (*b)[temp];
+        Return()
+    })
+}
+
+fn main() {
+    assert_eq!(unions(U { a: 5 }), 5);
+    assert_eq!(tuples((5, 6)), (5, 6));
+
+    assert_eq!(unwrap(Some(5)), 5);
+    assert_eq!(unwrap_deref(Some(&5)), 5);
+    let mut o = Some(5);
+    set(&mut o);
+    assert_eq!(o, Some(10));
+
+    assert_eq!(simple_index([0; 10], &[0; 10]), 0);
+}
diff --git a/src/test/mir-opt/building/custom/projections.set.built.after.mir b/src/test/mir-opt/building/custom/projections.set.built.after.mir
new file mode 100644
index 00000000000..2f15176a61f
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.set.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `set` after built
+
+fn set(_1: &mut Option<i32>) -> () {
+    let mut _0: ();                      // return place in scope 0 at $DIR/projections.rs:+0:31: +0:31
+
+    bb0: {
+        (((*_1) as variant#1).0: i32) = const 10_i32; // scope 0 at $DIR/projections.rs:+2:9: +2:48
+        return;                          // scope 0 at $DIR/projections.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.simple_index.built.after.mir b/src/test/mir-opt/building/custom/projections.simple_index.built.after.mir
new file mode 100644
index 00000000000..fc422e4b3f0
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.simple_index.built.after.mir
@@ -0,0 +1,13 @@
+// MIR for `simple_index` after built
+
+fn simple_index(_1: [i32; 10], _2: &[i32]) -> i32 {
+    let mut _0: i32;                     // return place in scope 0 at $DIR/projections.rs:+0:45: +0:48
+    let mut _3: usize;                   // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        _3 = const 3_usize;              // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+        _0 = _1[_3];                     // scope 0 at $DIR/projections.rs:+3:9: +3:22
+        _0 = (*_2)[_3];                  // scope 0 at $DIR/projections.rs:+4:9: +4:25
+        return;                          // scope 0 at $DIR/projections.rs:+5:9: +5:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.tuples.built.after.mir b/src/test/mir-opt/building/custom/projections.tuples.built.after.mir
new file mode 100644
index 00000000000..65487d3c9ed
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.tuples.built.after.mir
@@ -0,0 +1,13 @@
+// MIR for `tuples` after built
+
+fn tuples(_1: (u32, i32)) -> (u32, i32) {
+    let mut _0: (u32, i32);              // return place in scope 0 at $DIR/projections.rs:+0:29: +0:39
+    let mut _2: (u32, i32);              // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        (_2.0: u32) = (_1.0: u32);       // scope 0 at $DIR/projections.rs:+5:13: +5:25
+        (_2.1: i32) = (_1.1: i32);       // scope 0 at $DIR/projections.rs:+6:13: +6:25
+        _0 = _2;                         // scope 0 at $DIR/projections.rs:+8:13: +8:23
+        return;                          // scope 0 at $DIR/projections.rs:+9:13: +9:21
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.unions.built.after.mir b/src/test/mir-opt/building/custom/projections.unions.built.after.mir
new file mode 100644
index 00000000000..922538a5f17
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.unions.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `unions` after built
+
+fn unions(_1: U) -> i32 {
+    let mut _0: i32;                     // return place in scope 0 at $DIR/projections.rs:+0:20: +0:23
+
+    bb0: {
+        _0 = (_1.0: i32);                // scope 0 at $DIR/projections.rs:+2:9: +2:18
+        return;                          // scope 0 at $DIR/projections.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.unwrap.built.after.mir b/src/test/mir-opt/building/custom/projections.unwrap.built.after.mir
new file mode 100644
index 00000000000..75b03a3c393
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.unwrap.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `unwrap` after built
+
+fn unwrap(_1: Option<i32>) -> i32 {
+    let mut _0: i32;                     // return place in scope 0 at $DIR/projections.rs:+0:32: +0:35
+
+    bb0: {
+        _0 = ((_1 as variant#1).0: i32); // scope 0 at $DIR/projections.rs:+2:9: +2:40
+        return;                          // scope 0 at $DIR/projections.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/projections.unwrap_deref.built.after.mir b/src/test/mir-opt/building/custom/projections.unwrap_deref.built.after.mir
new file mode 100644
index 00000000000..c6b0f7efa9b
--- /dev/null
+++ b/src/test/mir-opt/building/custom/projections.unwrap_deref.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `unwrap_deref` after built
+
+fn unwrap_deref(_1: Option<&i32>) -> i32 {
+    let mut _0: i32;                     // return place in scope 0 at $DIR/projections.rs:+0:39: +0:42
+
+    bb0: {
+        _0 = (*((_1 as variant#1).0: &i32)); // scope 0 at $DIR/projections.rs:+2:9: +2:49
+        return;                          // scope 0 at $DIR/projections.rs:+3:9: +3:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/references.raw_pointer.built.after.mir b/src/test/mir-opt/building/custom/references.raw_pointer.built.after.mir
new file mode 100644
index 00000000000..775e5e3ad9b
--- /dev/null
+++ b/src/test/mir-opt/building/custom/references.raw_pointer.built.after.mir
@@ -0,0 +1,10 @@
+// MIR for `raw_pointer` after built
+
+fn raw_pointer(_1: *const i32) -> *const i32 {
+    let mut _0: *const i32;              // return place in scope 0 at $DIR/references.rs:+0:38: +0:48
+
+    bb0: {
+        _0 = &raw const (*_1);           // scope 0 at $DIR/references.rs:+4:9: +4:27
+        return;                          // scope 0 at $DIR/references.rs:+5:9: +5:17
+    }
+}
diff --git a/src/test/mir-opt/building/custom/references.rs b/src/test/mir-opt/building/custom/references.rs
index dee85722e86..c93f6ec624b 100644
--- a/src/test/mir-opt/building/custom/references.rs
+++ b/src/test/mir-opt/building/custom/references.rs
@@ -36,8 +36,22 @@ pub fn immut_ref(x: &i32) -> &i32 {
     )
 }
 
+// EMIT_MIR references.raw_pointer.built.after.mir
+#[custom_mir(dialect = "built")]
+pub fn raw_pointer(x: *const i32) -> *const i32 {
+    // Regression test for a bug in which unsafetyck was not correctly turned off for
+    // `dialect = "built"`
+    mir!({
+        RET = addr_of!(*x);
+        Return()
+    })
+}
+
 fn main() {
     let mut x = 5;
     assert_eq!(*mut_ref(&mut x), 5);
     assert_eq!(*immut_ref(&x), 5);
+    unsafe {
+        assert_eq!(*raw_pointer(addr_of!(x)), 5);
+    }
 }