[CIR] Implement lowering of int-to-bool casts (#132996)

Lowering of int-to-bool casts had been left as NYI because the incubator
implemented it by lowering to cir.cmp, which hasn't been upstreamed yet,
but there is no reason this cast can't be lowered directly to LLVM's
compare operation when we're lowering directly to the LLVM dialect.

This change lowers the cast directly to an LLVM compare to zero.

Author: andykaylor

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -383,13 +383,13 @@ mlir::LogicalResult CIRToLLVMCastOpLowering::matchAndRewrite(
     break;
   }
   case cir::CastKind::int_to_bool: {
-    assert(!cir::MissingFeatures::opCmp());
-    mlir::Type dstType = castOp.getResult().getType();
-    mlir::Type llvmDstType = getTypeConverter()->convertType(dstType);
-    auto zeroBool = rewriter.create<mlir::LLVM::ConstantOp>(
-        castOp.getLoc(), llvmDstType, mlir::BoolAttr::get(getContext(), false));
-    rewriter.replaceOp(castOp, zeroBool);
-    return castOp.emitError() << "NYI int_to_bool cast";
+    mlir::Value llvmSrcVal = adaptor.getOperands().front();
+    mlir::Value zeroInt = rewriter.create<mlir::LLVM::ConstantOp>(
+        castOp.getLoc(), llvmSrcVal.getType(),
+        mlir::IntegerAttr::get(llvmSrcVal.getType(), 0));
+    rewriter.replaceOpWithNewOp<mlir::LLVM::ICmpOp>(
+        castOp, mlir::LLVM::ICmpPredicate::ne, llvmSrcVal, zeroInt);
+    break;
   }
   case cir::CastKind::integral: {
     mlir::Type srcType = castOp.getSrc().getType();

clang/test/CIR/CodeGen/int-to-bool.cpp

@@ -0,0 +1,74 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG
+
+bool f1(unsigned char c) {
+  return c;
+}
+
+// CIR: cir.func @f1
+// CIR:   cir.cast(int_to_bool, %{{.*}} : !u8i), !cir.bool
+
+// Note: The full zext/store/load/trunc sequence is checked here to show what
+// CIR is being lowered to. There's no need to check it for every function since
+// the lowering is the same for all of them.
+
+// LLVM: define i1 @f1
+// LLVM:   %[[CMP:.*]] = icmp ne i8 %4, 0
+// LLVM:   %[[ZEXT:.*]] = zext i1 %[[CMP]] to i8
+// LLVM:   store i8 %[[ZEXT]], ptr %{{.*}}
+// LLVM:   %[[LOAD:.*]] = load i8, ptr %{{.*}}
+// LLVM:   %[[TRUNC:.*]] = trunc i8 %[[LOAD]] to i1
+// LLVM:   ret i1 %[[TRUNC]]
+
+// OGCG: define{{.*}} i1 @_Z2f1h
+// OGCG:   %[[CMP:.*]] = icmp ne i8 %{{.*}}, 0
+// OGCG:   ret i1 %[[CMP]]
+
+bool f2(short s) {
+  return s;
+}
+
+// CIR: cir.func @f2
+// CIR:   cir.cast(int_to_bool, %{{.*}} : !s16i), !cir.bool
+
+// LLVM: define i1 @f2
+// LLVM:   %[[CMP:.*]] = icmp ne i16 %4, 0
+// LLVM:   %[[ZEXT:.*]] = zext i1 %[[CMP]] to i8
+
+// OGCG: define{{.*}} i1 @_Z2f2s
+// OGCG:   %[[CMP:.*]] = icmp ne i16 %{{.*}}, 0
+// OGCG:   ret i1 %[[CMP]]
+
+bool f3(unsigned u) {
+  return u;
+}
+
+// CIR: cir.func @f3
+// CIR:   cir.cast(int_to_bool, %{{.*}} : !u32i), !cir.bool
+
+// LLVM: define i1 @f3
+// LLVM:   %[[CMP:.*]] = icmp ne i32 %4, 0
+// LLVM:   %[[ZEXT:.*]] = zext i1 %[[CMP]] to i8
+
+// OGCG: define{{.*}} i1 @_Z2f3j
+// OGCG:   %[[CMP:.*]] = icmp ne i32 %{{.*}}, 0
+// OGCG:   ret i1 %[[CMP]]
+
+bool f4(long l) {
+  return l;
+}
+
+// CIR: cir.func @f4
+// CIR:   cir.cast(int_to_bool, %{{.*}} : !s64i), !cir.bool
+
+// LLVM: define i1 @f4
+// LLVM:   %[[CMP:.*]] = icmp ne i64 %4, 0
+// LLVM:   %[[ZEXT:.*]] = zext i1 %[[CMP]] to i8
+
+// OGCG: define{{.*}} i1 @_Z2f4l
+// OGCG:   %[[CMP:.*]] = icmp ne i64 %{{.*}}, 0
+// OGCG:   ret i1 %[[CMP]]

clang/test/CIR/Lowering/cast.cir

@@ -47,6 +47,9 @@ module {
     %21 = cir.load %20 : !cir.ptr<!s16i>, !s16i
     %22 = cir.cast(integral, %21 : !s16i), !u64i
     // CHECK: %[[TMP:[0-9]+]] = llvm.sext %{{[0-9]+}} : i16 to i64
+    %33 = cir.cast(int_to_bool, %arg1 : !s32i), !cir.bool
+    // CHECK: %[[#ZERO:]] = llvm.mlir.constant(0 : i32) : i32
+    // CHECK: %[[#CMP:]] = llvm.icmp "ne" %arg1, %[[#ZERO]] : i32
 
     // Pointer casts.
     cir.store %16, %6 : !s64i, !cir.ptr<!s64i>