Implement casts

Signed-off-by: Anton Korobeynikov <[email protected]>
p4lang · Feb 10, 2025 · 404f787 · 404f787
1 parent 30758d1
commit 404f787
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Showing 3 changed files with 42 additions and 13 deletions.
diff --git a/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td b/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td
@@ -171,4 +171,28 @@ def StoreOp : P4HIR_Op<"store", [
   // FIXME: add verifier.
 }
 
+// TODO: Decide if we'd want to be more precise and split cast into
+// bitcast, trunc and extensions
+def CastOp : P4HIR_Op<"cast",
+             [Pure/*,
+              DeclareOpInterfaceMethods<PromotableOpInterface>*/]> {
+  let summary = "Conversion between values of different types";
+  let description = [{
+    Apply P4 usual conversions rules between values.
+    ```mlir
+    %4 = p4hir.cast (%3 : !p4hir:bit<32>) : !p4hir:int<32>
+    ```
+  }];
+
+  let arguments = (ins AnyP4Type:$src);
+  let results = (outs AnyP4Type:$result);
+
+  let assemblyFormat = [{
+    `(` $src `:` type($src) `)`
+    `:` type($result) attr-dict
+  }];
+
+  // FIXME: add verifier.
+}
+
 #endif // P4MLIR_DIALECT_P4HIR_P4HIR_OPS_TD
diff --git a/test/Translate/Ops/variables.p4 b/test/Translate/Ops/variables.p4
@@ -12,10 +12,9 @@ action foo() {
   bit<8> b5 = 8w0b_1010_1010; // same value as above
   bit<8> b6 = 8w170;          // same value as above
   bit<8> b7 = 8w0b1010_1010;  // an 8-bit unsigned number with value 170
-  // FIXME: Implement casts and path resolution
-  // int<8> b8 = (int<8>)b7;
+  int<8> b8 = (int<8>)b7;
   int<42> b9;
-  bit<8> b10 = b7;
+  bit<8> b10 = (bit<8>)b8;
 }
 
 // CHECK-LABEL: module   
@@ -40,7 +39,12 @@ action foo() {
 // CHECK:         %[[VAL_12:.*]] = p4hir.const #p4hir.int<170> : !p4hir.bit<8>
 // CHECK:         %[[VAL_13:.*]] = p4hir.alloca !p4hir.bit<8> ["b7", init] : !p4hir.ref<!p4hir.bit<8>>
 // CHECK:         p4hir.store %[[VAL_12]], %[[VAL_13]] : !p4hir.bit<8>, !p4hir.ref<!p4hir.bit<8>>
+// CHECK:         %[[VAL_14_1:.*]] = p4hir.load %[[VAL_13]] : !p4hir.ref<!p4hir.bit<8>>, !p4hir.bit<8>
+// CHECK:         %[[VAL_15_1:.*]] = p4hir.cast(%[[VAL_14_1]] : !p4hir.bit<8>) : !p4hir.int<8>
+// CHECK:         %[[VAL_16_1:.*]] = p4hir.alloca !p4hir.int<8> ["b8", init] : !p4hir.ref<!p4hir.int<8>>
+// CHECK:         p4hir.store %[[VAL_15_1]], %[[VAL_16_1]] : !p4hir.int<8>, !p4hir.ref<!p4hir.int<8>>
 // CHECK:         %[[VAL_14:.*]] = p4hir.alloca !p4hir.int<42> ["b9"] : !p4hir.ref<!p4hir.int<42>>
+// CHECK:         %[[VAL_14_2:.*]] = p4hir.load %[[VAL_16_1]] : !p4hir.ref<!p4hir.int<8>>, !p4hir.int<8>
+// CHECK:         %[[VAL_16:.*]] = p4hir.cast(%[[VAL_14_2]] : !p4hir.int<8>) : !p4hir.bit<8>
 // CHECK:         %[[VAL_15:.*]] = p4hir.alloca !p4hir.bit<8> ["b10", init] : !p4hir.ref<!p4hir.bit<8>>
-// CHECK:         %[[VAL_16:.*]] = p4hir.load %[[VAL_13]] : !p4hir.ref<!p4hir.bit<8>>, !p4hir.bit<8>
 // CHECK:         p4hir.store %[[VAL_16]], %[[VAL_15]] : !p4hir.bit<8>, !p4hir.ref<!p4hir.bit<8>>
diff --git a/tools/p4mlir-translate/translate.cpp b/tools/p4mlir-translate/translate.cpp
@@ -250,20 +250,13 @@ class P4HIRConverter : public P4::Inspector, public P4::ResolutionContext {
         return false;
     }
 
-    bool preorder(const P4::IR::Cast *cast) override {
-        // Cast could be used in constant initializers or as a separate
-        // operation. In former case resolve it to the constant
-        if (typeMap->isCompileTimeConstant(cast)) {
-            resolveConstantExpr(cast);
-            return false;
-        }
-        return true;
-    }
+    bool preorder(const P4::IR::Cast *cast) override { return true; }
 
     bool preorder(const P4::IR::Declaration_Constant *decl) override;
 
     bool preorder(const P4::IR::Declaration_Variable *) override { return true; }
     void postorder(const P4::IR::Declaration_Variable *decl) override;
+    void postorder(const P4::IR::Cast *cast) override;
 };
 
 bool P4TypeConverter::preorder(const P4::IR::Type_Bits *type) {
@@ -402,6 +395,14 @@ void P4HIRConverter::postorder(const P4::IR::Declaration_Variable *decl) {
     setValue(decl, alloca);
 }
 
+void P4HIRConverter::postorder(const P4::IR::Cast *cast) {
+    LOG4("Converting " << dbp(cast));
+    auto src = getValue(cast->expr);
+    auto destType = getOrCreateType(cast->destType);
+
+    setValue(cast, builder.create<P4HIR::CastOp>(getLoc(builder, cast), destType, src));
+}
+
 }  // namespace
 
 namespace P4::P4MLIR {