Rodrigo Mesquita pushed to branch wip/romes/step-out-5 at Glasgow Haskell Compiler / GHC

Commits:

6 changed files:

Changes:

  • compiler/GHC/ByteCode/Asm.hs
    ... ... @@ -858,7 +858,7 @@ assembleI platform i = case i of
    858 858 
                                                       , Op np
    859 859 
                                                       ]
    860 860
    861 
    -  BRK_INTERNAL active -> emit_ bci_BRK_INTERNAL [SmallOp active]
    861 
    +  BRK_ALTS active -> emit_ bci_BRK_ALTS [SmallOp active]
    862 862
    863 863 
     #if MIN_VERSION_rts(1,0,3)
    864 864 
       BCO_NAME name            -> do np <- lit1 (BCONPtrStr name)

  • compiler/GHC/ByteCode/Instr.hs
    ... ... @@ -272,9 +272,10 @@ data BCInstr
    272 272 
                           !UnitId                -- breakpoint info module unit id
    273 273 
                           !Word16                -- breakpoint info index
    274 274 
                           (RemotePtr CostCentre)
    275 
    -   -- An internal breakpoint should only be set by the compiler or RTS
    276 
    -   -- See Note [BRK_INTERNAL]
    277 
    -   | BRK_INTERNAL     !Word16 {- enabled? -}
    275 
    +
    276 
    +   -- An internal breakpoint for triggering a break on any case alternative
    277 
    +   -- See Note [Debugger: BRK_ALTS]
    278 
    +   | BRK_ALTS         !Word16 {- enabled? -}
    278 279
    279 280 
     #if MIN_VERSION_rts(1,0,3)
    280 281 
        -- | A "meta"-instruction for recording the name of a BCO for debugging purposes.
    ... ... @@ -471,7 +472,7 @@ instance Outputable BCInstr where
    471 472 
                                    <+> text "<tick_module>" <+> text "<tick_module_unitid>" <+> ppr tickx
    472 473 
                                    <+> text "<info_module>" <+> text "<info_module_unitid>" <+> ppr infox
    473 474 
                                    <+> text "<cc>"
    474 
    -   ppr (BRK_INTERNAL active) = text "BRK_INTERNAL" <+> ppr active
    475 
    +   ppr (BRK_ALTS active)     = text "BRK_ALTS" <+> ppr active
    475 476 
     #if MIN_VERSION_rts(1,0,3)
    476 477 
        ppr (BCO_NAME nm)         = text "BCO_NAME" <+> text (show nm)
    477 478 
     #endif
    ... ... @@ -597,7 +598,7 @@ bciStackUse OP_INDEX_ADDR{} = 0
    597 598
    598 599 
     bciStackUse SWIZZLE{}             = 0
    599 600 
     bciStackUse BRK_FUN{}             = 0
    600 
    -bciStackUse BRK_INTERNAL{}        = 0
    601 
    +bciStackUse BRK_ALTS{}            = 0
    601 602
    602 603 
     -- These insns actually reduce stack use, but we need the high-tide level,
    603 604 
     -- so can't use this info.  Not that it matters much.

  • compiler/GHC/StgToByteCode.hs
    ... ... @@ -1372,7 +1372,10 @@ doCase d s p scrut bndr alts
    1372 1372 
                | ubx_tuple_frame    = SLIDE 0 2 `consOL` alt_final0
    1373 1373 
                | otherwise          = alt_final0
    1374 1374 
              alt_final
    1375 
    -          = BRK_INTERNAL 0 `consOL` alt_final1
    1375 
    +           | gopt Opt_InsertBreakpoints (hsc_dflags hsc_env)
    1376 
    +                                -- See Note [Debugger: BRK_ALTS]
    1377 
    +                                = BRK_ALTS 0 `consOL` alt_final1
    1378 
    +           | otherwise          = alt_final1
    1376 1379
    1377 1380 
          add_bco_name <- shouldAddBcoName
    1378 1381 
          let
    ... ... @@ -1392,6 +1395,37 @@ doCase d s p scrut bndr alts
    1392 1395 
                       _     -> panic "schemeE(StgCase).push_alts"
    1393 1396 
                 in return (PUSH_ALTS alt_bco scrut_rep `consOL` scrut_code)
    1394 1397
    1398 
    +{-
    1399 
    +Note [Debugger: BRK_ALTS]
    1400 
    +~~~~~~~~~~~~~~~~~~~~~~~~~
    1401 
    +As described in Note [Debugger: Step-out] in rts/Interpreter.c, to implement
    1402 
    +the stepping-out debugger feature we traverse the heap at runtime, identify
    1403 
    +the continuation BCO, and explicitly enable that BCO's breakpoint thus ensuring
    1404 
    +we stop exactly when we return to the continuation.
    1405 
    +
    1406 
    +However, a case continuation BCO (pushed by PUSH_ALTS), which computes what
    1407 
    +case alternative BCO to take, never gets a user-facing breakpoint tick (BRK_FUN):
    1408 
    +
    1409 
    +  1) It's not useful to a user stepping through the program to always have a
    1410 
    +  breakpoint after the scrutinee is evaluated but before the case alternative
    1411 
    +  is selected. The associated source span would also be slightly awkward to choose.
    1412 
    +
    1413 
    +  2) It's not easy to add a source-tick before the case alternatives because in
    1414 
    +  essentially all internal representations they are given as a list of Alts
    1415 
    +  rather than an expression.
    1416 
    +
    1417 
    +To provide the debugger a way to enable at runtime the case continuation
    1418 
    +breakpoints regardless, we introduce at the start of every PUSH_ALTS BCO a
    1419 
    +BRK_ALTS instruction.
    1420 
    +
    1421 
    +The BRK_ALTS instruction, if enabled (by its single arg), ensures we stop at
    1422 
    +the breakpoint heading the case alternative we take. Under the hood, this means
    1423 
    +that when BRK_ALTS is enabled we set TSO_STOP_NEXT_BREAKPOINT just before
    1424 
    +selecting the alternative.
    1425 
    +
    1426 
    +It's important that BRK_ALTS (just like BRK_FUN) is the first instruction of
    1427 
    +the BCO, since that's where the debugger will look to enable it at runtime.
    1428 
    +-}
    1395 1429
    1396 1430 
     -- -----------------------------------------------------------------------------
    1397 1431 
     -- Deal with tuples

  • rts/Disassembler.c
    ... ... @@ -94,8 +94,8 @@ disInstr ( StgBCO *bco, int pc )
    94 94 
              debugBelch("\n");
    95 95 
              pc += 6;
    96 96 
              break;
    97 
    -      case bci_BRK_INTERNAL:
    98 
    -         debugBelch ("BRK_INTERNAL %d\n", BCO_NEXT);
    97 
    +      case bci_BRK_ALTS:
    98 
    +         debugBelch ("BRK_ALTS %d\n", BCO_NEXT);
    99 99 
              break;
    100 100 
           case bci_SWIZZLE: {
    101 101 
              W_     stkoff = BCO_GET_LARGE_ARG;

  • rts/Interpreter.c
    ... ... @@ -643,10 +643,12 @@ interpretBCO (Capability* cap)
    643 643 
                 // ACTIVATE the breakpoint by tick index
    644 644 
                 ((StgInt*)breakPoints->payload)[tick_index] = 0;
    645 645 
             }
    646 
    -        else if ((bco_instrs[0] & 0xFF) == bci_BRK_INTERNAL) {
    646 
    +        else if ((bco_instrs[0] & 0xFF) == bci_BRK_ALTS) {
    647 647 
                 // ACTIVATE BRK_ALTS by setting its only argument to ON
    648 648 
                 bco_instrs[1] = 1;
    649 649 
             }
    650 
    +        // else: if there is no BRK instruction perhaps we should keep
    651 
    +        // traversing; that said, the continuation should always have a BRK
    650 652 
           }
    651 653 
           else /* type == STOP_FRAME */ {
    652 654 
             /* No continuation frame to further stop at: Nothing to do */
    ... ... @@ -1588,14 +1590,11 @@ run_BCO:
    1588 1590 
                 goto nextInsn;
    1589 1591 
             }
    1590 1592
    1591 
    -        case bci_BRK_INTERNAL:
    1593 
    +        /* See Note [Debugger: BRK_ALTS] */
    1594 
    +        case bci_BRK_ALTS:
    1592 1595 
             {
    1593 
    -          printf("BREAK INTERNAL\n");
    1594 1596 
               StgWord16 active = BCO_NEXT;
    1595 
    -          printf("BREAK INTERNAL: %d\n", active);
    1596 1597 
               if (active) {
    1597 
    -            printf("BREAK INTERNAL is active\n");
    1598 
    -            // Break on next!
    1599 1598 
                 cap->r.rCurrentTSO->flags |= TSO_STOP_NEXT_BREAKPOINT;
    1600 1599 
               }
    1601 1600

  • rts/include/rts/Bytecodes.h
    ... ... @@ -214,7 +214,7 @@
    214 214 
     #define bci_OP_INDEX_ADDR_32           242
    215 215 
     #define bci_OP_INDEX_ADDR_64           243
    216 216
    217 
    -#define bci_BRK_INTERNAL               244
    217 
    +#define bci_BRK_ALTS                   244
    218 218
    219 219
    220 220 
     /* If you need to go past 255 then you will run into the flags */

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