[Mlir-commits] [mlir] [mlir][arith] Mark `arith.remsi` and `arith.remui` as conditionally speculatable (PR #188263)

[Matthias Springer]

https://github.com/matthias-springer updated https://github.com/llvm/llvm-project/pull/188263

>From c191ad0c87fa913c5b22a0f1c1cfd56288e10019 Mon Sep 17 00:00:00 2001
From: Matthias Springer <me at m-sp.org>
Date: Tue, 24 Mar 2026 14:55:30 +0000
Subject: [PATCH] [mlir][arith] Mark `arith.remsi` and `arith.remui` as
 conditionally speculatable

---
 mlir/include/mlir/Dialect/Arith/IR/ArithOps.td | 18 ++++++++++++++++--
 mlir/lib/Dialect/Arith/IR/ArithOps.cpp         | 13 +++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
index 4b830c05bf585..50a09761f110d 100644
--- a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
+++ b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
@@ -678,7 +678,8 @@ def Arith_FloorDivSIOp : Arith_TotalIntBinaryOp<"floordivsi"> {
 // RemUIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_RemUIOp : Arith_TotalIntBinaryOp<"remui"> {
+def Arith_RemUIOp : Arith_IntBinaryOp<"remui",
+                                      [ConditionallySpeculatable]> {
   let summary = "unsigned integer division remainder operation";
   let description = [{
     Unsigned integer division remainder. Treats the leading bit as the most
@@ -701,6 +702,12 @@ def Arith_RemUIOp : Arith_TotalIntBinaryOp<"remui"> {
     %x = arith.remui %y, %z : tensor<4x?xi8>
     ```
   }];
+
+  let extraClassDeclaration = [{
+    /// Interface method for ConditionallySpeculatable.
+    Speculation::Speculatability getSpeculatability();
+  }];
+
   let hasFolder = 1;
 }
 
@@ -708,7 +715,8 @@ def Arith_RemUIOp : Arith_TotalIntBinaryOp<"remui"> {
 // RemSIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_RemSIOp : Arith_TotalIntBinaryOp<"remsi"> {
+def Arith_RemSIOp : Arith_IntBinaryOp<"remsi",
+                                      [ConditionallySpeculatable]> {
   let summary = "signed integer division remainder operation";
   let description = [{
     Signed integer division remainder. Treats the leading bit as sign, i.e. `6 %
@@ -731,6 +739,12 @@ def Arith_RemSIOp : Arith_TotalIntBinaryOp<"remsi"> {
     %x = arith.remsi %y, %z : tensor<4x?xi8>
     ```
   }];
+
+  let extraClassDeclaration = [{
+    /// Interface method for ConditionallySpeculatable.
+    Speculation::Speculatability getSpeculatability();
+  }];
+
   let hasFolder = 1;
 }
 
diff --git a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
index 155edc5070a9d..105bdb9238c1b 100644
--- a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -931,6 +931,10 @@ OpFoldResult arith::RemUIOp::fold(FoldAdaptor adaptor) {
   return div0 ? Attribute() : result;
 }
 
+Speculation::Speculatability arith::RemUIOp::getSpeculatability() {
+  return getDivUISpeculatability(getRhs());
+}
+
 //===----------------------------------------------------------------------===//
 // RemSIOp
 //===----------------------------------------------------------------------===//
@@ -954,6 +958,15 @@ OpFoldResult arith::RemSIOp::fold(FoldAdaptor adaptor) {
   return div0 ? Attribute() : result;
 }
 
+Speculation::Speculatability arith::RemSIOp::getSpeculatability() {
+  // X % 0 => UB
+  // X % -1 is well-defined (always 0), unlike X / -1 which can overflow.
+  if (matchPattern(getRhs(), m_IntRangeWithoutZeroS()))
+    return Speculation::Speculatable;
+
+  return Speculation::NotSpeculatable;
+}
+
 //===----------------------------------------------------------------------===//
 // AndIOp
 //===----------------------------------------------------------------------===//