[Mlir-commits] [mlir] 917f078 - [mlir][Transforms] Allow RemoveDeadValues to process a function whose the last block is not the exit. (#156123)

[llvmlistbot at llvm.org]

Author: xin liu
Date: 2025-08-31T10:00:32Z
New Revision: 917f078adb3ffab4cf50aec3e13c977c092d7754

URL: https://github.com/llvm/llvm-project/commit/917f078adb3ffab4cf50aec3e13c977c092d7754
DIFF: https://github.com/llvm/llvm-project/commit/917f078adb3ffab4cf50aec3e13c977c092d7754.diff

LOG: [mlir][Transforms] Allow RemoveDeadValues to process a function whose the last block is not the exit. (#156123)

'processFuncOp' queries the number of returned values of a function
using the terminator of the last block's getNumOperands(). It presumes
the last block is the exit. It is not always the case. 
This patch fixes the bug by querying from FunctionInterfaceOp directly.

Added: 
    

Modified: 
    mlir/lib/Transforms/RemoveDeadValues.cpp
    mlir/test/Transforms/remove-dead-values.mlir

Removed: 
    


################################################################################
diff  --git a/mlir/lib/Transforms/RemoveDeadValues.cpp b/mlir/lib/Transforms/RemoveDeadValues.cpp
index 02dad69e49614..0e84b6dd17f29 100644
--- a/mlir/lib/Transforms/RemoveDeadValues.cpp
+++ b/mlir/lib/Transforms/RemoveDeadValues.cpp
@@ -344,8 +344,7 @@ static void processFuncOp(FunctionOpInterface funcOp, Operation *module,
   // being returned, in order to optimize our IR. So, this demonstrates how we
   // can make our optimization strong by even removing a live return value (%0),
   // since it forwards only to non-live value(s) (%1#1).
-  Operation *lastReturnOp = funcOp.back().getTerminator();
-  size_t numReturns = lastReturnOp->getNumOperands();
+  size_t numReturns = funcOp.getNumResults();
   BitVector nonLiveRets(numReturns, true);
   for (SymbolTable::SymbolUse use : uses) {
     Operation *callOp = use.getUser();

diff  --git a/mlir/test/Transforms/remove-dead-values.mlir b/mlir/test/Transforms/remove-dead-values.mlir
index 0f8d757086e87..fa2c145bd3701 100644
--- a/mlir/test/Transforms/remove-dead-values.mlir
+++ b/mlir/test/Transforms/remove-dead-values.mlir
@@ -592,3 +592,26 @@ module @dynamically_unreachable {
     return
   }
 }
+
+// CHECK-LABEL: module @last_block_not_exit
+module @last_block_not_exit {
+  // return value can be removed because it's private.
+  func.func private @terminated_with_condbr(%arg0: i1, %arg1: i1) -> i1 {
+    %true = arith.constant true
+    %false = arith.constant false
+    cf.cond_br %arg0, ^bb1(%false : i1), ^bb2
+  ^bb1(%1: i1):  // 2 preds: ^bb0, ^bb2
+    return %1 : i1
+  ^bb2:  // pred: ^bb3
+    cf.cond_br %arg1, ^bb1(%false : i1), ^bb1(%true : i1)
+  }
+
+  func.func public @call_private_but_not_use() {
+    %i0 = arith.constant 0: i1
+    %i1 = arith.constant 1: i1
+    call @terminated_with_condbr(%i0, %i1) : (i1, i1) -> i1
+    func.return
+  }
+  // CHECK-LABEL: @call_private_but_not_use
+  // CHECK: call @terminated_with_condbr(%false, %true) : (i1, i1)
+}