[CIR][CIRGen&LowerToLLVM] Support for dereferencing void pointers

Author: PragmaTwice

clang/lib/CIR/CodeGen/CIRGenStmt.cpp

@@ -487,7 +487,7 @@ mlir::LogicalResult CIRGenFunction::buildReturnStmt(const ReturnStmt &S) {
       // Make sure not to return anything, but evaluate the expression
       // for side effects.
       if (RV) {
-        assert(0 && "not implemented");
+        buildScalarExpr(RV);
       }
     } else if (!RV) {
       // Do nothing (return value is left uninitialized)

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

@@ -864,6 +864,13 @@ class CIRLoadLowering : public mlir::OpConversionPattern<mlir::cir::LoadOp> {
   mlir::LogicalResult
   matchAndRewrite(mlir::cir::LoadOp op, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override {
+    // if the result type is void, we can just remove the load operation since
+    // it's useless
+    if (op.getResult().getType().isa<mlir::cir::VoidType>()) {
+      rewriter.eraseOp(op);
+      return mlir::LogicalResult::success();
+    }
+
     const auto llvmTy =
         getTypeConverter()->convertType(op.getResult().getType());
     unsigned alignment = 0;

clang/test/CIR/CodeGen/pointer-arith-ext.c

@@ -55,8 +55,34 @@ void *f4_1(void *a, int b) { return (a -= b); }
 // FP f6_1(int a, FP b) { return (a += b); }
 // FP f7(FP a, int b) { return a - b; }
 // FP f7_1(FP a, int b) { return (a -= b); }
-// void f8(void *a, int b) { return *(a + b); }
-// void f8_1(void *a, int b) { return a[b]; }
+
+void f8(void *a, int b) { return *(a + b); }
+// CIR-LABEL: f8
+// CIR: %[[PTR:.*]] = cir.load {{.*}} : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
+// CIR: %[[STRIDE:.*]] = cir.load {{.*}} : !cir.ptr<!s32i>, !s32i
+// CIR: cir.ptr_stride(%[[PTR]] : !cir.ptr<!void>, %[[STRIDE]] : !s32i)
+// CIR: cir.return
+
+// LLVM-LABEL: f8
+// LLVM: %[[PTR:.*]] = load ptr, ptr {{.*}}, align 8
+// LLVM: %[[TOEXT:.*]] = load i32, ptr {{.*}}, align 4
+// LLVM: %[[STRIDE:.*]] = sext i32 %[[TOEXT]] to i64
+// LLVM: getelementptr i8, ptr %[[PTR]], i64 %[[STRIDE]]
+// LLVM: ret void
+
+void f8_1(void *a, int b) { return a[b]; }
+// CIR-LABEL: f8_1
+// CIR: %[[PTR:.*]] = cir.load {{.*}} : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
+// CIR: %[[STRIDE:.*]] = cir.load {{.*}} : !cir.ptr<!s32i>, !s32i
+// CIR: cir.ptr_stride(%[[PTR]] : !cir.ptr<!void>, %[[STRIDE]] : !s32i)
+// CIR: cir.return
+
+// LLVM-LABEL: f8_1
+// LLVM: %[[PTR:.*]] = load ptr, ptr {{.*}}, align 8
+// LLVM: %[[TOEXT:.*]] = load i32, ptr {{.*}}, align 4
+// LLVM: %[[STRIDE:.*]] = sext i32 %[[TOEXT]] to i64
+// LLVM: getelementptr i8, ptr %[[PTR]], i64 %[[STRIDE]]
+// LLVM: ret void
 
 unsigned char *p(unsigned int x) {
   unsigned char *p;