[Lldb-commits] [lldb] [lldb] Implement WebAssembly debugging (PR #77949)

[Greg Clayton via lldb-commits]

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@@ -2595,6 +2604,37 @@ bool DWARFExpression::Evaluate(
       break;
     }
 
+    case DW_OP_WASM_location: {
+      uint8_t wasm_op = opcodes.GetU8(&offset);
+      uint32_t index;
+
+      /* LLDB doesn't have an address space to represents WebAssembly locals,
+       * globals and operand stacks.
+       * We encode these elements into virtual registers:
+       *   | tag: 2 bits | index: 30 bits |
+       *   where tag is:
+       *    0: Not a WebAssembly location
+       *    1: Local
+       *    2: Global
+       *    3: Operand stack value
+       */
+      if (wasm_op == 3) {
+        index = opcodes.GetU32(&offset);
+        wasm_op = 2; // Global
+      } else {
+        index = opcodes.GetULEB128(&offset);
+      }
+
+      reg_num = (((wasm_op + 1) & 0x03) << 30) | (index & 0x3fffffff);
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clayborg wrote:

Why are we adding 1 to the wasm_op? Can't we just set it correctly above?

Also it would be nice to have an enum or constant for `0x03` like `kWasmOpMask`,  and for `30` like `kWasmOpShift'

https://github.com/llvm/llvm-project/pull/77949