[Mlir-commits] [mlir] [MLIR] Fix outdated restriction comment in RemoveDeadValuesPass (PR #189041)

[Mehdi Amini]

https://github.com/joker-eph created https://github.com/llvm/llvm-project/pull/189041

The RemoveDeadValuesPass previously emitted an error and skipped
optimization when the IR contained non-function symbol ops, non-call
symbol user ops, or branch ops. This restriction was later removed, but
the comments in RemoveDeadValues.cpp and Passes.td still described the
pass as operating "iff the IR doesn't have any non-function symbol ops,
non-call symbol user ops and branch ops."

Remove the stale restriction text from both the .cpp file comment and
the Passes.td description. Also add a test that verifies dead function
arguments are correctly removed inside a module that defines a symbol
(has a sym_name attribute), which was the original failure case reported
in issue #98700.

Fixes #98700

Assisted-by: Claude Code

>From d49dfdd21ebd4bbc22a4191a04b7ee11b6f4c1b7 Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph at gmail.com>
Date: Fri, 27 Mar 2026 06:52:10 -0700
Subject: [PATCH] [MLIR] Fix outdated restriction comment in
 RemoveDeadValuesPass

The RemoveDeadValuesPass previously emitted an error and skipped
optimization when the IR contained non-function symbol ops, non-call
symbol user ops, or branch ops. This restriction was later removed, but
the comments in RemoveDeadValues.cpp and Passes.td still described the
pass as operating "iff the IR doesn't have any non-function symbol ops,
non-call symbol user ops and branch ops."

Remove the stale restriction text from both the .cpp file comment and
the Passes.td description. Also add a test that verifies dead function
arguments are correctly removed inside a module that defines a symbol
(has a sym_name attribute), which was the original failure case reported
in issue #98700.

Fixes #98700

Assisted-by: Claude Code
---
 mlir/include/mlir/Transforms/Passes.td       |  7 +------
 mlir/lib/Transforms/RemoveDeadValues.cpp     |  7 +------
 mlir/test/Transforms/remove-dead-values.mlir | 21 ++++++++++++++++++++
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/mlir/include/mlir/Transforms/Passes.td b/mlir/include/mlir/Transforms/Passes.td
index 8a6228e00aa03..1474e580cfc03 100644
--- a/mlir/include/mlir/Transforms/Passes.td
+++ b/mlir/include/mlir/Transforms/Passes.td
@@ -106,12 +106,7 @@ def RemoveDeadValuesPass : Pass<"remove-dead-values"> {
     (C) Removes unneccesary operands, results, region arguments, and region
     terminator operands of region branch ops, and,
     (D) Removes simple and region branch ops that have all non-live results and
-    don't affect memory in any way,
-
-    iff
-
-    the IR doesn't have any non-function symbol ops, non-call symbol user ops
-    and branch ops.
+    don't affect memory in any way.
 
     Here, a "simple op" refers to an op that isn't a symbol op, symbol-user op,
     region branch op, branch op, region branch terminator op, or return-like.
diff --git a/mlir/lib/Transforms/RemoveDeadValues.cpp b/mlir/lib/Transforms/RemoveDeadValues.cpp
index ade7647890830..f0a210a2ededb 100644
--- a/mlir/lib/Transforms/RemoveDeadValues.cpp
+++ b/mlir/lib/Transforms/RemoveDeadValues.cpp
@@ -19,12 +19,7 @@
 // (C) Removes unneccesary operands, results, region arguments, and region
 // terminator operands of region branch ops, and,
 // (D) Removes simple and region branch ops that have all non-live results and
-// don't affect memory in any way,
-//
-// iff
-//
-// the IR doesn't have any non-function symbol ops, non-call symbol user ops and
-// branch ops.
+// don't affect memory in any way.
 //
 // Here, a "simple op" refers to an op that isn't a symbol op, symbol-user op,
 // region branch op, branch op, region branch terminator op, or return-like.
diff --git a/mlir/test/Transforms/remove-dead-values.mlir b/mlir/test/Transforms/remove-dead-values.mlir
index 19bc6b2fddd66..64088ce15cd48 100644
--- a/mlir/test/Transforms/remove-dead-values.mlir
+++ b/mlir/test/Transforms/remove-dead-values.mlir
@@ -29,6 +29,27 @@ module @named_module_acceptable {
 
 // -----
 
+// Dead function arguments are removed even if the enclosing module defines a
+// symbol (has a sym_name attribute). Fixes #98700.
+//
+// CHECK: func.func private @compute(%arg0: i32) -> i32
+// CHECK-NOT: %dead_arg
+module @named_module_with_dead_args {
+  func.func private @compute(%arg0: i32, %dead_arg: i32) -> i32 {
+    return %arg0 : i32
+  }
+  // CHECK: func.func @main() -> i32
+  func.func @main() -> i32 {
+    %c1 = arith.constant 1 : i32
+    %c2 = arith.constant 2 : i32
+    // CHECK: call @compute(%c1_i32) : (i32) -> i32
+    %result = call @compute(%c1, %c2) : (i32, i32) -> i32
+    return %result : i32
+  }
+}
+
+// -----
+
 // The IR contains both conditional and unconditional branches with a loop
 // in which the last cf.cond_br is referncing the first cf.br
 //