Auto merge of #132527 - DianQK:gvn-stmt-iter, r=oli-obk

gvn: Invalid dereferences for all non-local mutations

Fixes #132353.

This PR removes the computation value by traversing SSA locals through `for_each_assignment_mut`.

Because the `for_each_assignment_mut` traversal skips statements which have side effects, such as dereference assignments, the computation may be unsound. Instead of `for_each_assignment_mut`, we compute values by traversing in reverse postorder.

Because we compute and use the symbolic representation of values on the fly, I invalidate all old values when encountering a dereference assignment. The current approach does not prevent the optimization of a clone to a copy.

In the future, we may add an alias model, or dominance information for dereference assignments, or SSA form to help GVN.

r? cjgillot

cc `@jieyouxu` #132356
cc `@RalfJung` #133474

2 files changed, 24 insertions, 16 deletions

diff --git a/tests/codegen/clone_as_copy.rs b/tests/codegen/clone_as_copy.rs
index c39f120044c..ef834ef5912 100644
--- a/tests/codegen/clone_as_copy.rs
+++ b/tests/codegen/clone_as_copy.rs
@@ -1,6 +1,4 @@
 //@ revisions: DEBUGINFO NODEBUGINFO
-//@ compile-flags: -Zunsound-mir-opts
-// FIXME: see <https://github.com/rust-lang/rust/issues/132353>
 //@ compile-flags: -Copt-level=3 -Cno-prepopulate-passes
 //@ [DEBUGINFO] compile-flags: -Cdebuginfo=full
 
diff --git a/tests/codegen/try_question_mark_nop.rs b/tests/codegen/try_question_mark_nop.rs
index 3a3453b22b4..9430465a286 100644
--- a/tests/codegen/try_question_mark_nop.rs
+++ b/tests/codegen/try_question_mark_nop.rs
@@ -16,12 +16,17 @@ use std::ptr::NonNull;
 #[no_mangle]
 pub fn option_nop_match_32(x: Option<u32>) -> Option<u32> {
     // CHECK: start:
-    // TWENTY-NEXT: %[[IS_SOME:.+]] = trunc nuw i32 %0 to i1
-    // TWENTY-NEXT: %[[PAYLOAD:.+]] = select i1 %[[IS_SOME]], i32 %1, i32 undef
-    // CHECK-NEXT: [[REG1:%.*]] = insertvalue { i32, i32 } poison, i32 %0, 0
-    // NINETEEN-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } [[REG1]], i32 %1, 1
-    // TWENTY-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } [[REG1]], i32 %[[PAYLOAD]], 1
-    // CHECK-NEXT: ret { i32, i32 } [[REG2]]
+    // CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i32 %0 to i1
+
+    // NINETEEN-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i32 %0, i32 0
+    // NINETEEN-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } poison, i32 [[SELECT]], 0
+    // NINETEEN-NEXT: [[REG3:%.*]] = insertvalue { i32, i32 } [[REG2]], i32 %1, 1
+
+    // TWENTY-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i32 %1, i32 undef
+    // TWENTY-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } poison, i32 %0, 0
+    // TWENTY-NEXT: [[REG3:%.*]] = insertvalue { i32, i32 } [[REG2]], i32 [[SELECT]], 1
+
+    // CHECK-NEXT: ret { i32, i32 } [[REG3]]
     match x {
         Some(x) => Some(x),
         None => None,
@@ -90,12 +95,17 @@ pub fn control_flow_nop_traits_32(x: ControlFlow<i32, u32>) -> ControlFlow<i32,
 #[no_mangle]
 pub fn option_nop_match_64(x: Option<u64>) -> Option<u64> {
     // CHECK: start:
-    // TWENTY-NEXT: %[[TRUNC:[0-9]+]] = trunc nuw i64 %0 to i1
-    // TWENTY-NEXT: %[[SEL:\.[0-9]+]] = select i1 %[[TRUNC]], i64 %1, i64 undef
-    // CHECK-NEXT: [[REG1:%[0-9a-zA-Z_.]+]] = insertvalue { i64, i64 } poison, i64 %0, 0
-    // NINETEEN-NEXT: [[REG2:%[0-9a-zA-Z_.]+]] = insertvalue { i64, i64 } [[REG1]], i64 %1, 1
-    // TWENTY-NEXT: [[REG2:%[0-9a-zA-Z_.]+]] = insertvalue { i64, i64 } [[REG1]], i64 %[[SEL]], 1
-    // CHECK-NEXT: ret { i64, i64 } [[REG2]]
+    // CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i64 %0 to i1
+
+    // NINETEEN-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i64 %0, i64 0
+    // NINETEEN-NEXT: [[REG2:%.*]] = insertvalue { i64, i64 } poison, i64 [[SELECT]], 0
+    // NINETEEN-NEXT: [[REG3:%.*]] = insertvalue { i64, i64 } [[REG2]], i64 %1, 1
+
+    // TWENTY-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i64 %1, i64 undef
+    // TWENTY-NEXT: [[REG2:%.*]] = insertvalue { i64, i64 } poison, i64 %0, 0
+    // TWENTY-NEXT: [[REG3:%.*]] = insertvalue { i64, i64 } [[REG2]], i64 [[SELECT]], 1
+
+    // CHECK-NEXT: ret { i64, i64 } [[REG3]]
     match x {
         Some(x) => Some(x),
         None => None,
@@ -164,8 +174,8 @@ pub fn control_flow_nop_traits_64(x: ControlFlow<i64, u64>) -> ControlFlow<i64,
 #[no_mangle]
 pub fn result_nop_match_128(x: Result<i128, u128>) -> Result<i128, u128> {
     // CHECK: start:
-    // CHECK-NEXT: getelementptr inbounds {{(nuw )?}}i8
     // CHECK-NEXT: store i128
+    // CHECK-NEXT: getelementptr inbounds {{(nuw )?}}i8
     // CHECK-NEXT: store i128
     // CHECK-NEXT: ret void
     match x {
@@ -189,8 +199,8 @@ pub fn result_nop_traits_128(x: Result<i128, u128>) -> Result<i128, u128> {
 #[no_mangle]
 pub fn control_flow_nop_match_128(x: ControlFlow<i128, u128>) -> ControlFlow<i128, u128> {
     // CHECK: start:
-    // CHECK-NEXT: getelementptr inbounds {{(nuw )?}}i8
     // CHECK-NEXT: store i128
+    // CHECK-NEXT: getelementptr inbounds {{(nuw )?}}i8
     // CHECK-NEXT: store i128
     // CHECK-NEXT: ret void
     match x {