Auto merge of #111344 - cjgillot:gvn-simplify, r=<try>

Perform opportunistic simplifications during value numbering Based on #109597 Opening mostly for discussion. In its current form, I think this pass does too much. I want to remove the const-propagation part to make it simpler.
rust-lang · Dec 30, 2023 · 01915ea · 01915ea
2 parents d59f06f + 935e283
commit 01915ea
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Showing 90 changed files with 2,693 additions and 1,094 deletions.
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -416,7 +416,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
     }
 
-    fn unsize_into(
+    pub fn unsize_into(
         &mut self,
         src: &OpTy<'tcx, M::Provenance>,
         cast_ty: TyAndLayout<'tcx>,

diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
diff --git a/tests/mir-opt/const_allocation.main.GVN.after.32bit.mir b/tests/mir-opt/const_allocation.main.GVN.after.32bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC9: &&[(Option<i32>, &[&str])]};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_allocation.main.GVN.after.64bit.mir b/tests/mir-opt/const_allocation.main.GVN.after.64bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC9: &&[(Option<i32>, &[&str])]};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_allocation2.main.GVN.after.32bit.mir b/tests/mir-opt/const_allocation2.main.GVN.after.32bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC9: &&[(Option<i32>, &[&u8])]};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_allocation2.main.GVN.after.64bit.mir b/tests/mir-opt/const_allocation2.main.GVN.after.64bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC9: &&[(Option<i32>, &[&u8])]};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_allocation3.main.GVN.after.32bit.mir b/tests/mir-opt/const_allocation3.main.GVN.after.32bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC4: &&Packed};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_allocation3.main.GVN.after.64bit.mir b/tests/mir-opt/const_allocation3.main.GVN.after.64bit.mir
@@ -7,10 +7,10 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        nop;
+        StorageLive(_2);
         _2 = const {ALLOC2: &&Packed};
         _1 = (*_2);
-        nop;
+        StorageDead(_2);
         StorageDead(_1);
         _0 = const ();
         return;

diff --git a/tests/mir-opt/const_prop/address_of_pair.fn0.GVN.diff b/tests/mir-opt/const_prop/address_of_pair.fn0.GVN.diff
@@ -24,9 +24,8 @@
       bb0: {
           StorageLive(_2);
 -         _2 = (const 1_i32, const false);
--         StorageLive(_3);
 +         _2 = const (1_i32, false);
-+         nop;
+          StorageLive(_3);
           _3 = &raw mut (_2.1: bool);
 -         _2 = (const 1_i32, const false);
 +         _2 = const (1_i32, false);
@@ -42,9 +41,8 @@
           StorageDead(_6);
           _0 = _5;
 -         StorageDead(_5);
--         StorageDead(_3);
-+         nop;
 +         nop;
+          StorageDead(_3);
           StorageDead(_2);
           return;
       }

diff --git a/tests/mir-opt/const_prop/array_index.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/const_prop/array_index.main.GVN.32bit.panic-abort.diff
@@ -18,11 +18,12 @@
           _2 = [const 0_u32, const 1_u32, const 2_u32, const 3_u32];
           StorageLive(_3);
           _3 = const 2_usize;
-          _4 = Len(_2);
+-         _4 = Len(_2);
 -         _5 = Lt(_3, _4);
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
-+         _5 = Lt(const 2_usize, _4);
-+         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, const 2_usize) -> [success: bb1, unwind unreachable];
++         _4 = const 4_usize;
++         _5 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind unreachable];
       }
 
       bb1: {

diff --git a/tests/mir-opt/const_prop/array_index.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/const_prop/array_index.main.GVN.32bit.panic-unwind.diff
@@ -18,11 +18,12 @@
           _2 = [const 0_u32, const 1_u32, const 2_u32, const 3_u32];
           StorageLive(_3);
           _3 = const 2_usize;
-          _4 = Len(_2);
+-         _4 = Len(_2);
 -         _5 = Lt(_3, _4);
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
-+         _5 = Lt(const 2_usize, _4);
-+         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, const 2_usize) -> [success: bb1, unwind continue];
++         _4 = const 4_usize;
++         _5 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind continue];
       }
 
       bb1: {

diff --git a/tests/mir-opt/const_prop/array_index.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/const_prop/array_index.main.GVN.64bit.panic-abort.diff
@@ -18,11 +18,12 @@
           _2 = [const 0_u32, const 1_u32, const 2_u32, const 3_u32];
           StorageLive(_3);
           _3 = const 2_usize;
-          _4 = Len(_2);
+-         _4 = Len(_2);
 -         _5 = Lt(_3, _4);
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
-+         _5 = Lt(const 2_usize, _4);
-+         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, const 2_usize) -> [success: bb1, unwind unreachable];
++         _4 = const 4_usize;
++         _5 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind unreachable];
       }
 
       bb1: {

diff --git a/tests/mir-opt/const_prop/array_index.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/const_prop/array_index.main.GVN.64bit.panic-unwind.diff
@@ -18,11 +18,12 @@
           _2 = [const 0_u32, const 1_u32, const 2_u32, const 3_u32];
           StorageLive(_3);
           _3 = const 2_usize;
-          _4 = Len(_2);
+-         _4 = Len(_2);
 -         _5 = Lt(_3, _4);
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
-+         _5 = Lt(const 2_usize, _4);
-+         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, const 2_usize) -> [success: bb1, unwind continue];
++         _4 = const 4_usize;
++         _5 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind continue];
       }
 
       bb1: {

diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff
@@ -22,18 +22,15 @@
       }
 
       bb0: {
--         StorageLive(_1);
-+         nop;
+          StorageLive(_1);
           StorageLive(_2);
--         StorageLive(_3);
-+         nop;
+          StorageLive(_3);
           _9 = const _;
           _3 = &(*_9);
           _2 = &raw const (*_3);
           _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
           StorageDead(_2);
--         StorageDead(_3);
-+         nop;
+          StorageDead(_3);
           StorageLive(_5);
           StorageLive(_6);
           _6 = const 3_usize;
@@ -50,8 +47,7 @@
           StorageDead(_6);
           _0 = const ();
           StorageDead(_5);
--         StorageDead(_1);
-+         nop;
+          StorageDead(_1);
           return;
       }
   }

diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff
@@ -22,18 +22,15 @@
       }
 
       bb0: {
--         StorageLive(_1);
-+         nop;
+          StorageLive(_1);
           StorageLive(_2);
--         StorageLive(_3);
-+         nop;
+          StorageLive(_3);
           _9 = const _;
           _3 = &(*_9);
           _2 = &raw const (*_3);
           _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
           StorageDead(_2);
--         StorageDead(_3);
-+         nop;
+          StorageDead(_3);
           StorageLive(_5);
           StorageLive(_6);
           _6 = const 3_usize;
@@ -50,8 +47,7 @@
           StorageDead(_6);
           _0 = const ();
           StorageDead(_5);
--         StorageDead(_1);
-+         nop;
+          StorageDead(_1);
           return;
       }
   }

diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff
@@ -22,18 +22,15 @@
       }
 
       bb0: {
--         StorageLive(_1);
-+         nop;
+          StorageLive(_1);
           StorageLive(_2);
--         StorageLive(_3);
-+         nop;
+          StorageLive(_3);
           _9 = const _;
           _3 = &(*_9);
           _2 = &raw const (*_3);
           _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
           StorageDead(_2);
--         StorageDead(_3);
-+         nop;
+          StorageDead(_3);
           StorageLive(_5);
           StorageLive(_6);
           _6 = const 3_usize;
@@ -50,8 +47,7 @@
           StorageDead(_6);
           _0 = const ();
           StorageDead(_5);
--         StorageDead(_1);
-+         nop;
+          StorageDead(_1);
           return;
       }
   }

diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff
@@ -22,18 +22,15 @@
       }
 
       bb0: {
--         StorageLive(_1);
-+         nop;
+          StorageLive(_1);
           StorageLive(_2);
--         StorageLive(_3);
-+         nop;
+          StorageLive(_3);
           _9 = const _;
           _3 = &(*_9);
           _2 = &raw const (*_3);
           _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
           StorageDead(_2);
--         StorageDead(_3);
-+         nop;
+          StorageDead(_3);
           StorageLive(_5);
           StorageLive(_6);
           _6 = const 3_usize;
@@ -50,8 +47,7 @@
           StorageDead(_6);
           _0 = const ();
           StorageDead(_5);
--         StorageDead(_1);
-+         nop;
+          StorageDead(_1);
           return;
       }
   }

diff --git a/tests/mir-opt/const_prop/boolean_identities.rs b/tests/mir-opt/const_prop/boolean_identities.rs
@@ -5,10 +5,9 @@ pub fn test(x: bool, y: bool) -> bool {
     // CHECK-LABEL: fn test(
     // CHECK: debug a => [[a:_.*]];
     // CHECK: debug b => [[b:_.*]];
-    // FIXME(cjgillot) simplify algebraic identity
-    // CHECK-NOT: [[a]] = const true;
-    // CHECK-NOT: [[b]] = const false;
-    // CHECK-NOT: _0 = const false;
+    // CHECK: [[a]] = const true;
+    // CHECK: [[b]] = const false;
+    // CHECK: _0 = const false;
     let a = (y | true);
     let b = (x & false);
     a & b

diff --git a/tests/mir-opt/const_prop/boolean_identities.test.GVN.diff b/tests/mir-opt/const_prop/boolean_identities.test.GVN.diff
@@ -24,21 +24,23 @@
           StorageLive(_4);
           _4 = _2;
 -         _3 = BitOr(move _4, const true);
-+         _3 = BitOr(_2, const true);
++         _3 = const true;
           StorageDead(_4);
 -         StorageLive(_5);
 +         nop;
           StorageLive(_6);
           _6 = _1;
 -         _5 = BitAnd(move _6, const false);
-+         _5 = BitAnd(_1, const false);
++         _5 = const false;
           StorageDead(_6);
           StorageLive(_7);
-          _7 = _3;
+-         _7 = _3;
++         _7 = const true;
           StorageLive(_8);
-          _8 = _5;
+-         _8 = _5;
 -         _0 = BitAnd(move _7, move _8);
-+         _0 = BitAnd(_3, _5);
++         _8 = const false;
++         _0 = const false;
           StorageDead(_8);
           StorageDead(_7);
 -         StorageDead(_5);

diff --git a/tests/mir-opt/const_prop/boxes.main.GVN.panic-abort.diff b/tests/mir-opt/const_prop/boxes.main.GVN.panic-abort.diff
@@ -20,7 +20,8 @@
 
       bb0: {
           StorageLive(_1);
-          StorageLive(_2);
+-         StorageLive(_2);
++         nop;
           StorageLive(_3);
 -         _4 = SizeOf(i32);
 -         _5 = AlignOf(i32);
@@ -39,8 +40,10 @@
           StorageDead(_7);
           _9 = (((_3.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32);
           _2 = (*_9);
-          _1 = Add(move _2, const 0_i32);
-          StorageDead(_2);
+-         _1 = Add(move _2, const 0_i32);
+-         StorageDead(_2);
++         _1 = _2;
++         nop;
           drop(_3) -> [return: bb2, unwind unreachable];
       }
 

diff --git a/tests/mir-opt/const_prop/boxes.main.GVN.panic-unwind.diff b/tests/mir-opt/const_prop/boxes.main.GVN.panic-unwind.diff
@@ -20,7 +20,8 @@
 
       bb0: {
           StorageLive(_1);
-          StorageLive(_2);
+-         StorageLive(_2);
++         nop;
           StorageLive(_3);
 -         _4 = SizeOf(i32);
 -         _5 = AlignOf(i32);
@@ -39,8 +40,10 @@
           StorageDead(_7);
           _9 = (((_3.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32);
           _2 = (*_9);
-          _1 = Add(move _2, const 0_i32);
-          StorageDead(_2);
+-         _1 = Add(move _2, const 0_i32);
+-         StorageDead(_2);
++         _1 = _2;
++         nop;
           drop(_3) -> [return: bb2, unwind: bb3];
       }
 

diff --git a/tests/mir-opt/const_prop/boxes.rs b/tests/mir-opt/const_prop/boxes.rs
@@ -12,7 +12,7 @@ fn main() {
     // CHECK: debug x => [[x:_.*]];
     // CHECK: (*{{_.*}}) = const 42_i32;
     // CHECK: [[tmp:_.*]] = (*{{_.*}});
-    // CHECK: [[x]] = Add(move [[tmp]], const 0_i32);
+    // CHECK: [[x]] = [[tmp]];
     let x = *(#[rustc_box]
     Box::new(42))
         + 0;