[mlir][tosa] Interpret boolean values correctly in cast folder

[lhutton1]

Previously the cast folder would sign extend boolean values, leading "true" to be casted to a value of -1 instead of 1. This change ensures i1 values are zero extended, since i1 is used as a boolean value in TOSA. According to the TOSA spec, the result of a boolean cast with value "true" to another integer type should give a result of 1.

Fixes #57951

[llvmbot]

@llvm/pr-subscribers-mlir-tosa

@llvm/pr-subscribers-mlir

Author: Luke Hutton (lhutton1)

Changes

Previously the cast folder would sign extend boolean values, leading "true" to be casted to a value of -1 instead of 1. This change ensures i1 values are zero extended, since i1 is used as a boolean value in TOSA. According to the TOSA spec, the result of a boolean cast with value "true" to another integer type should give a result of 1.

Fixes #57951

---

Full diff: https://github.com/llvm/llvm-project/pull/147078.diff

2 Files Affected:

• (modified) mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp (+4-2)
• (modified) mlir/test/Dialect/Tosa/canonicalize.mlir (+11)

diff --git a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
index 1d21096e8920b..e2a2f2935b6b4 100644
--- a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
+++ b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
@@ -1301,7 +1301,8 @@ OpFoldResult CastOp::fold(FoldAdaptor adaptor) {
     }
 
     if (llvm::isa<IntegerType>(inETy) && llvm::isa<IntegerType>(outETy)) {
-      auto unsignIn = llvm::cast<IntegerType>(inETy).isUnsignedInteger();
+      const auto inIntType = llvm::cast<IntegerType>(inETy);
+      auto unsignIn = inIntType.isUnsignedInteger();
       bool trunc =
           inETy.getIntOrFloatBitWidth() > outETy.getIntOrFloatBitWidth();
       auto intVal = operand.getSplatValue<APInt>();
@@ -1309,7 +1310,8 @@ OpFoldResult CastOp::fold(FoldAdaptor adaptor) {
 
       if (trunc) {
         intVal = intVal.trunc(bitwidth);
-      } else if (unsignIn) {
+      // i1 types are boolean in TOSA
+      } else if (unsignIn || inIntType.isInteger(1)) {
         intVal = intVal.zext(bitwidth);
       } else {
         intVal = intVal.sext(bitwidth);
diff --git a/mlir/test/Dialect/Tosa/canonicalize.mlir b/mlir/test/Dialect/Tosa/canonicalize.mlir
index 27280807b0282..11c8d54fda055 100644
--- a/mlir/test/Dialect/Tosa/canonicalize.mlir
+++ b/mlir/test/Dialect/Tosa/canonicalize.mlir
@@ -1338,3 +1338,14 @@ func.func @no_fold_mul_result_exceeds_i32() -> tensor<i32> {
     %3 = tosa.mul %0, %1, %2 : (tensor<i32>, tensor<i32>, tensor<1xi8>) -> tensor<i32>
     return %3 : tensor<i32>
 }
+
+// -----
+
+// CHECK-LABEL: @test_fold_i1_to_i32_cast
+// CHECK: %[[OUT:.*]] = "tosa.const"() <{values = dense<1> : tensor<i32>}> : () -> tensor<i32>
+// CHECK: return %[[OUT]] : tensor<i32>
+func.func @test_fold_i1_to_i32_cast() -> tensor<i32> {
+  %0 = "tosa.const"() <{values = dense<1> : tensor<i1>}> : () -> tensor<i1>
+  %1 = "tosa.cast"(%0) : (tensor<i1>) -> tensor<i32>
+  return %1 : tensor<i32>
+}

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.