add readme

2 files changed, 115 insertions, 0 deletions

diff --git a/Parser.y b/Parser.y
index 82999fb..8bc1546 100644
--- a/Parser.y
+++ b/Parser.y
@@ -290,6 +290,7 @@ l3_expression
     : l4_operator l3_expression             {$$=std::make_shared<pcc::UnaryExprNode>(ctx,$1,$2);}
     | AT lvalue                             {$$=$2;}
     | standalone                            {$$=$1;}
+    ;
 
 standalone
     : rvalue                                {$$=$1;}
diff --git a/README.nd b/README.nd
new file mode 100644
index 0000000..75827a9
--- /dev/null
+++ b/README.nd
@@ -0,0 +1,114 @@
+# pcc - simple pascal-like compiler based on LLVM
+
+## How to build
+
+### linux & macOS & FreeBSD
+
+- download the LLVM 10.0.0 prebuilt binary at [LLVM release page](https://releases.llvm.org/download.html#10.0.0)
+- extract the tarball
+- make a build directory under the source directory
+- run `cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH=/path/to/the/llvm/`
+- run `cmake --build . -j8`
+
+### windows
+
+- get the awesome package manager [vcpkg](https://github.com/Microsoft/vcpkg)
+- run .\vcpkg.exe install llvm:x64-windows
+- make a build directory under the source directory
+- run `cmake .. -DCMAKE_TOOLCHIAN_FILE=/path/to/your/vcpkg/toolchain/file`
+- run `cmake --build . -j8`
+
+### How to run
+
+```
+Usage: pcc [-vVhiScad] [-O <0,1,2,3>] [-o <output>] file...
+    -v            Verbose mode.
+    -vv           Very verbose mode.
+    -V            Show version and exit.
+    -h            Show this help and exit.
+
+    -i            Generate LLVM IR (default behavior).
+    -S            Compile to assembly file.
+    -c            Compile to object file.
+    -o <output>   Specify output file name.
+    -O <0,1,2,3>  Specify optimization level.
+
+    -a            Dump the AST.
+    -d            Generate a dot file for AST.
+```
+
+You can find some examples at the t directory.
+
+#### compile pascal file to executable
+
+```
+./pcc -c qsort.pas
+```
+
+Then you need to link the object file qsort.o by your host-compiler.
+
+- gcc case: `gcc -no-pie qsort.o`
+- clang case: `clang qsort.o`
+- msvc case: find the developer command window, use cl to link
+
+#### calling C functions from pascal
+
+See ssl.pas and extern.pas.
+
+For the `scanf` case, the `scanf` may be a marco in C like `__isoc99_scanf`, so you may need to wrap the scanf function, see common.pas.
+
+#### calling pascal functions from C
+
+See sha1.pas and sha1_driver.pas.
+
+### How to get the tree or graph view of AST
+
+pass -a to pcc, you will get a tree view of AST like this:
+
+```
+  `-FunctionNode FunctionName=main ReturnType=integer
+    |-VarDeclNode local size=2
+    | |-Variable name=arr type=integer[100000]
+    | `-Variable name=i type=integer
+    `-StatementListNode size=5
+      |-FunctionCallNode FunctionName=srand ResultType=void
+      | `-FunctionCallNode FunctionName=time ResultType=integer
+      |   `-IntegerLiteralNode value=0
+      |-ForStatementNode direction=up
+      | |-IdentifierNode lvalue name=i type=^integer
+      | |-IntegerLiteralNode value=0
+      | |-IntegerLiteralNode value=99999
+      | `-AssignStatementNode ValueType=int64
+      |   |-ArrayAccessNode ResultType=^integer
+      |   | |-IdentifierNode lvalue name=arr type=^integer[100000]
+      |   | `-L2RCastingNode ResultType=integer
+      |   |   `-IdentifierNode lvalue name=i type=^integer
+      |   `-BinaryExprNode op='%' ResultType=int64
+      |     |-FunctionCallNode FunctionName=rand ResultType=integer
+      |     `-IntegerLiteralNode value=1000
+      |-FunctionCallNode FunctionName=qsort ResultType=void
+      | |-IdentifierNode lvalue name=arr type=^integer[100000]
+      | |-IntegerLiteralNode value=0
+      | `-IntegerLiteralNode value=99999
+      |-ForStatementNode direction=down
+      | |-IdentifierNode lvalue name=i type=^integer
+      | |-IntegerLiteralNode value=99999
+      | |-IntegerLiteralNode value=0
+      | `-FunctionCallNode FunctionName=printf ResultType=integer
+      |   |-StringLiteralNode value='%d \x00'
+      |   `-L2RCastingNode ResultType=integer
+      |     `-ArrayAccessNode ResultType=^integer
+      |       |-IdentifierNode lvalue name=arr type=^integer[100000]
+      |       `-L2RCastingNode ResultType=integer
+      |         `-IdentifierNode lvalue name=i type=^integer
+      `-AssignStatementNode ValueType=int64
+        |-IdentifierNode lvalue name=main type=^integer
+        `-IntegerLiteralNode value=0
+```
+
+pass -d to pcc, it will generate a dot file, use graphviz to render it.
+
+```
+pcc -d qsort.pas
+dot -Tpng -o qsort.png qsort.dot
+```