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

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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
This commit is contained in:
bors 2025-04-03 19:17:33 +00:00
commit 00095b3da4
43 changed files with 567 additions and 574 deletions
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2
tests/codegen/clone_as_copy.rs
View file

@ -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

38
tests/codegen/try_question_mark_nop.rs
View file

@ -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 {