[code-reflection] RFR: 8324789: Add line number information to code models

[Paul Sandoz]

On Thu, 18 Apr 2024 10:52:00 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Enable operations to have originating source location information, specifically source reference, line and column information.
>> 
>> The location information may be set (one or more times) on an operation while it is unbound. Once it is bound, when it is a member of a block and that block is bound, it can no longer be set. Copying an operation will also copy the location. This enables preservation when transforming, especially for lowering.
>> 
>> The compiler generates location information from a tree node, and sets it on the associated operation(s). For the operations associated with a reflected method (FuncOp) or quoted lambda expression (LambdaOp or ClosureOp) the source reference (a URI) is added to the location, whereas for all other operations the source reference is absent.
>> 
>> Example:
>> 
>> 
>>     @CodeReflection                          // 47
>>     static int f(int n) {                    // 48
>>         int sum = 0;                         // 49
>>         for (int i = 0; i < n; i++)  {       // 50
>>             sum += i;                        // 51
>>         }                                    // 52
>>         return sum;                          // 53
>>     }                                        // 54
>> 
>> 
>> Model:
>> 
>> 
>> func @"f" @loc="47:5:file:///Users/sandoz/Projects/jdk/test/babylon-test/src/test/java/T.java" (%0 : int)int -> {
>>     %1 : Var<int> = var %0 @"n" @loc="47:5";
>>     %2 : int = constant @"0" @loc="49:19";
>>     %3 : Var<int> = var %2 @"sum" @loc="49:9";
>>     java.for @loc="50:9"
>>         ()Var<int> -> {
>>             %4 : int = constant @"0" @loc="50:22";
>>             %5 : Var<int> = var %4 @"i" @loc="50:14";
>>             yield %5 @loc="50:9";
>>         }
>>         (%6 : Var<int>)boolean -> {
>>             %7 : int = var.load %6 @loc="50:25";
>>             %8 : int = var.load %1 @loc="50:29";
>>             %9 : boolean = lt %7 %8 @loc="50:25";
>>             yield %9 @loc="50:9";
>>         }
>>         (%10 : Var<int>)void -> {
>>             %11 : int = var.load %10 @loc="50:32";
>>             %12 : int = constant @"1" @loc="50:32";
>>             %13 : int = add %11 %12 @loc="50:32";
>>             var.store %10 %13 @loc="50:32";
>>             yield @loc="50:9";
>>         }
>>         (%14 : Var<int>)void -> {
>>             %15 : int = var.load %3 @loc="51:13";
>>             %16 : int = var.load %14 @loc="51:20";
>>             %17 : int = add %15 %16 @loc="51:13";
>>             var.store %3 %17 @loc="51:13";
>>           ...
>
> src/java.base/share/classes/java/lang/reflect/code/Op.java line 268:
> 
>> 266:      * {@return the originating source location of this operation, otherwise {@code null} if not specified}
>> 267:      */
>> 268:     public final Location location() {
> 
> Should this be returning `Optional`? Or, do we want to have a "no position" (like javac has)?

I was pondering aliasing `null`, such as `static final Location NOLOCATION = null`.

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PR Review Comment: https://git.openjdk.org/babylon/pull/54#discussion_r1570972522