[Mlir-commits] [mlir] [mlir][tosa] Fix integer-to-boolean cast folder (PR #150370)

[Longsheng Mou]

https://github.com/CoTinker updated https://github.com/llvm/llvm-project/pull/150370

>From b7f11d0864f3ee71c3a8348ca8cb9d6f8560fbc3 Mon Sep 17 00:00:00 2001
From: Longsheng Mou <longshengmou at gmail.com>
Date: Thu, 24 Jul 2025 12:24:26 +0800
Subject: [PATCH 1/3] [mlir][tosa] Fix integer-to-boolean cast folder
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

According to the TOSA spec, casting to boolean should produce true if the input is non-zero, and false otherwise — i.e., `out = (in != 0) ? true : false`. Previous behavior incorrectly relied on truncation, which could yield incorrect results for non-zero values whose least significant bit is zero.
---
 mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
index 606626dfe4d2c..080955bf94761 100644
--- a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
+++ b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
@@ -1302,9 +1302,13 @@ OpFoldResult CastOp::fold(FoldAdaptor adaptor) {
       auto intVal = operand.getSplatValue<APInt>();
       auto bitwidth = outETy.getIntOrFloatBitWidth();
 
+      // i1 types are boolean in TOSA
       if (trunc) {
-        intVal = intVal.trunc(bitwidth);
-        // i1 types are boolean in TOSA
+        if (outETy.isInteger(1)) {
+          intVal = intVal.isZero() ? APInt(bitwidth, 0) : APInt(bitwidth, 1);
+        } else {
+          intVal = intVal.trunc(bitwidth);
+        }
       } else if (unsignIn || inIntType.isInteger(1)) {
         intVal = intVal.zext(bitwidth);
       } else {

>From 304fa75706cccf208fd0b0cab249090cb7688900 Mon Sep 17 00:00:00 2001
From: Longsheng Mou <longshengmou at gmail.com>
Date: Thu, 24 Jul 2025 12:28:57 +0800
Subject: [PATCH 2/3] add test

---
 mlir/test/Dialect/Tosa/canonicalize.mlir | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mlir/test/Dialect/Tosa/canonicalize.mlir b/mlir/test/Dialect/Tosa/canonicalize.mlir
index 11c8d54fda055..6b55442a82a0a 100644
--- a/mlir/test/Dialect/Tosa/canonicalize.mlir
+++ b/mlir/test/Dialect/Tosa/canonicalize.mlir
@@ -1349,3 +1349,14 @@ func.func @test_fold_i1_to_i32_cast() -> tensor<i32> {
   %1 = "tosa.cast"(%0) : (tensor<i1>) -> tensor<i32>
   return %1 : tensor<i32>
 }
+
+// -----
+
+// CHECK-LABEL: @test_fold_i32_to_i1_cast
+// CHECK: %[[OUT:.*]] = "tosa.const"() <{values = dense<true> : tensor<i1>}> : () -> tensor<i1>
+// CHECK: return %[[OUT]] : tensor<i1>
+func.func @test_fold_i32_to_i1_cast() -> tensor<i1> {
+  %0 = "tosa.const"() <{values = dense<10> : tensor<i32>}> : () -> tensor<i32>
+  %1 = "tosa.cast"(%0) : (tensor<i32>) -> tensor<i1>
+  return %1 : tensor<i1>
+}

>From e7a8c0cca5354071a1ea04c596d3598a11213945 Mon Sep 17 00:00:00 2001
From: Longsheng Mou <longshengmou at gmail.com>
Date: Thu, 24 Jul 2025 14:13:10 +0800
Subject: [PATCH 3/3] simplify code

---
 mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
index 080955bf94761..dd99bb8f8e5c3 100644
--- a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
+++ b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
@@ -1305,7 +1305,7 @@ OpFoldResult CastOp::fold(FoldAdaptor adaptor) {
       // i1 types are boolean in TOSA
       if (trunc) {
         if (outETy.isInteger(1)) {
-          intVal = intVal.isZero() ? APInt(bitwidth, 0) : APInt(bitwidth, 1);
+          intVal = APInt(bitwidth, intVal.isZero() ? 0 : 1);
         } else {
           intVal = intVal.trunc(bitwidth);
         }