Change syntax for delete() function

A value is now deleted by calling: delete(@x)

README.md

@@ -41,7 +41,7 @@ kprobe:sys_read
 kretprobe:sys_read / @start[tid] /
 {
   @times = quantize(nsecs - @start[tid]);
-  @start[tid] = delete();
+  delete(@start[tid]);
 }
 ```
 ```
@@ -203,7 +203,7 @@ Variables:
 Functions:
 - `quantize(int n)` - Produce a log2 histogram of values of `n`
 - `count()` - Count the number of times this function is called
-- `delete()` - Delete the map element this is assigned to
+- `delete(@x)` - Delete the map element passed in as an argument
 - `str(char *s)` - Returns the string pointed to by `s`
 - `printf(char *fmt, ...)` - Write to stdout
 - `sym(void *p)` - Resolve kernel address

src/ast/ast.h

@@ -25,6 +25,7 @@ public:
   Variable *var = nullptr; // Set when this expression is assigned to a variable
   bool is_literal = false;
   bool is_variable = false;
+  bool is_map = false;
 };
 using ExpressionList = std::vector<Expression *>;
 
@@ -64,8 +65,8 @@ public:
 
 class Map : public Expression {
 public:
-  explicit Map(std::string &ident) : ident(ident), vargs(nullptr) { }
-  Map(std::string &ident, ExpressionList *vargs) : ident(ident), vargs(vargs) { }
+  explicit Map(std::string &ident) : ident(ident), vargs(nullptr) { is_map = true; }
+  Map(std::string &ident, ExpressionList *vargs) : ident(ident), vargs(vargs) { is_map = true; }
   std::string ident;
   ExpressionList *vargs;
 

src/ast/codegen_llvm.cpp

@@ -138,7 +138,8 @@ void CodegenLLVM::visit(Call &call)
   }
   else if (call.func == "delete")
   {
-    Map &map = *call.map;
+    auto &arg = *call.vargs->at(0);
+    auto &map = static_cast<Map&>(arg);
     AllocaInst *key = getMapKey(map);
     b_.CreateMapDeleteElem(map, key);
     b_.CreateLifetimeEnd(key);

src/ast/semantic_analyser.cpp

@@ -95,10 +95,14 @@ void SemanticAnalyser::visit(Call &call)
     call.type = SizedType(Type::count, 8);
   }
   else if (call.func == "delete") {
-    check_assignment(call, true, false);
-    check_nargs(call, 0);
+    check_assignment(call, false, false);
+    if (check_nargs(call, 1)) {
+      auto &arg = *call.vargs->at(0);
+      if (!arg.is_map)
+        err_ << "delete() expects a map to be provided" << std::endl;
+    }
 
-    call.type = SizedType(Type::del, 0);
+    call.type = SizedType(Type::none, 0);
   }
   else if (call.func == "str" || call.func == "sym" || call.func == "usym") {
     check_nargs(call, 1);
@@ -324,8 +328,7 @@ void SemanticAnalyser::visit(AssignMapStatement &assignment)
         search->second = assignment.expr->type;
       }
     }
-    else if (search->second.type != assignment.expr->type.type &&
-             assignment.expr->type.type != Type::del) {
+    else if (search->second.type != assignment.expr->type.type) {
       err_ << "Type mismatch for " << map_ident << ": ";
       err_ << "trying to assign value of type '" << assignment.expr->type;
       err_ << "'\n\twhen map already contains a value of type '";
@@ -367,8 +370,7 @@ void SemanticAnalyser::visit(AssignVarStatement &assignment)
         search->second = assignment.expr->type;
       }
     }
-    else if (search->second.type != assignment.expr->type.type &&
-             assignment.expr->type.type != Type::del) {
+    else if (search->second.type != assignment.expr->type.type) {
       err_ << "Type mismatch for " << var_ident << ": ";
       err_ << "trying to assign value of type '" << assignment.expr->type;
       err_ << "'\n\twhen variable already contains a value of type '";

src/types.h

@@ -14,7 +14,6 @@ const int STRING_SIZE = 64;
 enum class Type
 {
   none,
-  del,
   integer,
   quantize,
   count,

tests/codegen.cpp

@@ -856,7 +856,7 @@ attributes #1 = { argmemonly nounwind }
 
 TEST(codegen, call_delete)
 {
-  test("kprobe:f { @x = delete() }",
+  test("kprobe:f { @x = 1; delete(@x) }",
 
 R"EXPECTED(; Function Attrs: nounwind
 declare i64 @llvm.bpf.pseudo(i64, i64) #0
@@ -866,13 +866,25 @@ declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
 
 define i64 @"kprobe:f"(i8* nocapture readnone) local_unnamed_addr section "s_kprobe:f" {
 entry:
+  %"@x_key1" = alloca i64, align 8
+  %"@x_val" = alloca i64, align 8
   %"@x_key" = alloca i64, align 8
   %1 = bitcast i64* %"@x_key" to i8*
   call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %1)
   store i64 0, i64* %"@x_key", align 8
+  %2 = bitcast i64* %"@x_val" to i8*
+  call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %2)
+  store i64 1, i64* %"@x_val", align 8
   %pseudo = tail call i64 @llvm.bpf.pseudo(i64 1, i64 1)
-  %delete_elem = call i64 inttoptr (i64 3 to i64 (i8*, i8*)*)(i64 %pseudo, i64* nonnull %"@x_key")
+  %update_elem = call i64 inttoptr (i64 2 to i64 (i8*, i8*, i8*, i64)*)(i64 %pseudo, i64* nonnull %"@x_key", i64* nonnull %"@x_val", i64 0)
   call void @llvm.lifetime.end.p0i8(i64 -1, i8* nonnull %1)
+  call void @llvm.lifetime.end.p0i8(i64 -1, i8* nonnull %2)
+  %3 = bitcast i64* %"@x_key1" to i8*
+  call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %3)
+  store i64 0, i64* %"@x_key1", align 8
+  %pseudo2 = call i64 @llvm.bpf.pseudo(i64 1, i64 1)
+  %delete_elem = call i64 inttoptr (i64 3 to i64 (i8*, i8*)*)(i64 %pseudo2, i64* nonnull %"@x_key1")
+  call void @llvm.lifetime.end.p0i8(i64 -1, i8* nonnull %3)
   ret i64 0
 }
 

tests/semantic_analyser.cpp

@@ -80,7 +80,7 @@ TEST(semantic_analyser, builtin_functions)
 {
   test("kprobe:f { @x = quantize(123) }", 0);
   test("kprobe:f { @x = count() }", 0);
-  test("kprobe:f { @x = delete() }", 0);
+  test("kprobe:f { @x = 1; delete(@x) }", 0);
   test("kprobe:f { str(0xffff) }", 0);
   test("kprobe:f { printf(\"hello\\n\") }", 0);
   test("kprobe:f { sym(0xffff) }", 0);
@@ -116,7 +116,6 @@ TEST(semantic_analyser, mismatched_call_types)
 {
   test("kprobe:f { @x = 1; @x = count(); }", 1);
   test("kprobe:f { @x = 1; @x = quantize(0); }", 1);
-  test("kprobe:f { @x = 1; @x = delete(); }", 0);
 }
 
 TEST(semantic_analyser, call_quantize)
@@ -135,9 +134,11 @@ TEST(semantic_analyser, call_count)
 
 TEST(semantic_analyser, call_delete)
 {
-  test("kprobe:f { @x = delete(); }", 0);
-  test("kprobe:f { @x = delete(1); }", 1);
+  test("kprobe:f { @x = 1; delete(@x); }", 0);
+  test("kprobe:f { delete(1); }", 1);
   test("kprobe:f { delete(); }", 1);
+  test("kprobe:f { @y = delete(@x); }", 1);
+  test("kprobe:f { $y = delete(@x); }", 1);
 }
 
 TEST(semantic_analyser, call_str)

tools/biosnoop.bt

@@ -29,12 +29,12 @@ kprobe:blk_account_io_completion
 	    ($now - @epoch) / 1000000, @iocomm[arg0], @iopid[arg0],
 	    ($now - @start[arg0]) / 1000000);
 
-	@start[arg0] = delete();
-	@iopid[arg0] = delete();
-	@iocomm[arg0] = delete();
+	delete(@start[arg0]);
+	delete(@iopid[arg0]);
+	delete(@iocomm[arg0]);
 }
 
 END
 {
-	@epoch = delete();
+	delete(@epoch);
 }

tools/execsnoop.bt

@@ -38,5 +38,5 @@ kprobe:sys_execve
 
 END
 {
-	@epoch = delete();
+	delete(@epoch);
 }