Commit fb4a5ccdee

Veikka Tuominen <git@vexu.eu>
2022-11-30 18:31:01
llvm: make debuggers actually usable
`@llvm.dbg.value` is absolutely useless, adding a temporary alloca to store the constant in will make it actually show up in debuggers. The effect on performance should be minimal since there is only one store and it the change is not applied to ReleaseSafe builds. ```zig fn foo(a: u32, b: []const u8, c: bool, d: enum { yes, no }) void { _ = a; _ = b; _ = c; _ = d; } ``` before: ``` Breakpoint 1, a.foo (a=<optimized out>, b=..., c=<optimized out>, d=<optimized out>) at a.zig:18 18 _ = d; ``` after: ``` Breakpoint 1, a.foo (a=1, b=..., c=false, d=yes) at a.zig:15 15 _ = a; _ = b; _ = c; _ = d; (gdb) p b $1 = {ptr = 0x20854f <a.main.anon_3888> "bar", len = 3} ```
master
1 parent e4fd9ac
Changed files (1)
src
codegen
llvm.zig
src/codegen/llvm.zig
@@ -6088,6 +6088,12 @@ pub const FuncGen = struct {
         const insert_block = self.builder.getInsertBlock();
         if (isByRef(operand_ty)) {
             _ = dib.insertDeclareAtEnd(operand, di_local_var, debug_loc, insert_block);
+        } else if (self.dg.module.comp.bin_file.options.optimize_mode == .Debug) {
+            const alignment = operand_ty.abiAlignment(self.dg.module.getTarget());
+            const alloca = self.buildAlloca(operand.typeOf(), alignment);
+            const store_inst = self.builder.buildStore(operand, alloca);
+            store_inst.setAlignment(alignment);
+            _ = dib.insertDeclareAtEnd(alloca, di_local_var, debug_loc, insert_block);
         } else {
             _ = dib.insertDbgValueIntrinsicAtEnd(operand, di_local_var, debug_loc, insert_block);
         }
@@ -8026,6 +8032,12 @@ pub const FuncGen = struct {
             const insert_block = self.builder.getInsertBlock();
             if (isByRef(inst_ty)) {
                 _ = dib.insertDeclareAtEnd(arg_val, di_local_var, debug_loc, insert_block);
+            } else if (self.dg.module.comp.bin_file.options.optimize_mode == .Debug) {
+                const alignment = inst_ty.abiAlignment(self.dg.module.getTarget());
+                const alloca = self.buildAlloca(arg_val.typeOf(), alignment);
+                const store_inst = self.builder.buildStore(arg_val, alloca);
+                store_inst.setAlignment(alignment);
+                _ = dib.insertDeclareAtEnd(alloca, di_local_var, debug_loc, insert_block);
             } else {
                 _ = dib.insertDbgValueIntrinsicAtEnd(arg_val, di_local_var, debug_loc, insert_block);
             }