diff options
| -rw-r--r-- | generic/tclOptimize.c | 208 |
1 files changed, 127 insertions, 81 deletions
diff --git a/generic/tclOptimize.c b/generic/tclOptimize.c index 3e0d351..7d4226e 100644 --- a/generic/tclOptimize.c +++ b/generic/tclOptimize.c @@ -17,8 +17,11 @@ * Forward declarations. */ +static void AdvanceJumps(CompileEnv *envPtr); +static void ConvertZeroEffectToNOP(CompileEnv *envPtr); static void LocateTargetAddresses(CompileEnv *envPtr, Tcl_HashTable *tablePtr); +static void TrimUnreachable(CompileEnv *envPtr); /* * Helper macros. @@ -142,27 +145,67 @@ LocateTargetAddresses( /* * ---------------------------------------------------------------------- * - * TclOptimizeBytecode -- + * TrimUnreachable -- * - * A very simple peephole optimizer for bytecode. + * Converts code that provably can't be executed into NOPs and reduces + * the overall reported length of the bytecode where that is possible. * * ---------------------------------------------------------------------- */ -void -TclOptimizeBytecode( +static void +TrimUnreachable( CompileEnv *envPtr) { unsigned char *currentInstPtr; - int size; Tcl_HashTable targets; - /* - * Replace PUSH/POP sequences (when non-hazardous) with NOPs. Also replace - * PUSH empty/CONCAT and TRY_CVT_NUMERIC (when followed by an operation - * that guarantees the check for arithmeticity) and eliminate LNOT when we - * can invert the following JUMP condition. - */ + LocateTargetAddresses(envPtr, &targets); + + for (currentInstPtr = envPtr->codeStart ; + currentInstPtr < envPtr->codeNext-1 ; + currentInstPtr += AddrLength(currentInstPtr)) { + int clear = 0; + + if (*currentInstPtr != INST_DONE) { + continue; + } + + while (!IsTargetAddress(&targets, currentInstPtr + 1 + clear)) { + clear += AddrLength(currentInstPtr + 1 + clear); + } + if (currentInstPtr + 1 + clear == envPtr->codeNext) { + envPtr->codeNext -= clear; + } else { + while (clear --> 0) { + *(currentInstPtr + 1 + clear) = INST_NOP; + } + } + } + + Tcl_DeleteHashTable(&targets); +} + +/* + * ---------------------------------------------------------------------- + * + * ConvertZeroEffectToNOP -- + * + * Replace PUSH/POP sequences (when non-hazardous) with NOPs. Also + * replace PUSH empty/CONCAT and TRY_CVT_NUMERIC (when followed by an + * operation that guarantees the check for arithmeticity) and eliminate + * LNOT when we can invert the following JUMP condition. + * + * ---------------------------------------------------------------------- + */ + +static void +ConvertZeroEffectToNOP( + CompileEnv *envPtr) +{ + unsigned char *currentInstPtr; + int size; + Tcl_HashTable targets; LocateTargetAddresses(envPtr, &targets); for (currentInstPtr = envPtr->codeStart ; @@ -211,6 +254,7 @@ TclOptimizeBytecode( } } break; + case INST_LNOT: switch (nextInst) { case INST_JUMP_TRUE1: @@ -231,6 +275,7 @@ TclOptimizeBytecode( break; } break; + case INST_TRY_CVT_TO_NUMERIC: switch (nextInst) { case INST_JUMP_TRUE1: @@ -271,6 +316,7 @@ TclOptimizeBytecode( } break; } + if (blank > 0) { for (i=0 ; i<blank ; i++) { *(currentInstPtr + i) = INST_NOP; @@ -279,10 +325,25 @@ TclOptimizeBytecode( } } Tcl_DeleteHashTable(&targets); +} + +/* + * ---------------------------------------------------------------------- + * + * AdvanceJumps -- + * + * Advance jumps past NOPs and chained JUMPs. After this runs, the only + * JUMPs that jump to a NOP or a JUMP will be length-1 ones that run out + * of room in their opcode to be targeted to where they really belong. + * + * ---------------------------------------------------------------------- + */ - /* - * Advance jumps past NOPs and chained JUMPs. - */ +static void +AdvanceJumps( + CompileEnv *envPtr) +{ + unsigned char *currentInstPtr; for (currentInstPtr = envPtr->codeStart ; currentInstPtr < envPtr->codeNext-1 ; @@ -294,82 +355,67 @@ TclOptimizeBytecode( case INST_JUMP_TRUE1: case INST_JUMP_FALSE1: offset = TclGetInt1AtPtr(currentInstPtr + 1); - delta = 0; - advanceNext1: - if (offset + delta == 0) { - continue; - } - if (offset + delta < -128 || offset + delta > 127) { - TclStoreInt1AtPtr(offset, currentInstPtr + 1); - continue; - } - offset += delta; - switch (*(currentInstPtr + offset)) { - case INST_NOP: - delta = InstLength(INST_NOP); - goto advanceNext1; - case INST_JUMP1: - delta = TclGetInt1AtPtr(currentInstPtr + offset + 1); - goto advanceNext1; - case INST_JUMP4: - delta = TclGetInt4AtPtr(currentInstPtr + offset + 1); - goto advanceNext1; - default: - TclStoreInt1AtPtr(offset, currentInstPtr + 1); - continue; + for (delta=0 ; offset+delta != 0 ;) { + if (offset + delta < -128 || offset + delta > 127) { + break; + } + offset += delta; + switch (*(currentInstPtr + offset)) { + case INST_NOP: + delta = InstLength(INST_NOP); + continue; + case INST_JUMP1: + delta = TclGetInt1AtPtr(currentInstPtr + offset + 1); + continue; + case INST_JUMP4: + delta = TclGetInt4AtPtr(currentInstPtr + offset + 1); + continue; + } + break; } + TclStoreInt1AtPtr(offset, currentInstPtr + 1); + continue; + case INST_JUMP4: case INST_JUMP_TRUE4: case INST_JUMP_FALSE4: - offset = TclGetInt4AtPtr(currentInstPtr + 1); - advanceNext4: - if (offset == 0) { - continue; - } - switch (*(currentInstPtr + offset)) { - case INST_NOP: - offset += InstLength(INST_NOP); - goto advanceNext4; - case INST_JUMP1: - offset += TclGetInt1AtPtr(currentInstPtr + offset + 1); - goto advanceNext4; - case INST_JUMP4: - offset += TclGetInt4AtPtr(currentInstPtr + offset + 1); - goto advanceNext4; - default: - TclStoreInt4AtPtr(offset, currentInstPtr + 1); - continue; + for (offset = TclGetInt4AtPtr(currentInstPtr + 1); offset!=0 ;) { + switch (*(currentInstPtr + offset)) { + case INST_NOP: + offset += InstLength(INST_NOP); + continue; + case INST_JUMP1: + offset += TclGetInt1AtPtr(currentInstPtr + offset + 1); + continue; + case INST_JUMP4: + offset += TclGetInt4AtPtr(currentInstPtr + offset + 1); + continue; + } + break; } - } - } - - /* - * Trim unreachable instructions after a DONE. - */ - - LocateTargetAddresses(envPtr, &targets); - for (currentInstPtr = envPtr->codeStart ; - currentInstPtr < envPtr->codeNext-1 ; - currentInstPtr += AddrLength(currentInstPtr)) { - int clear = 0; - - if (*currentInstPtr != INST_DONE) { + TclStoreInt4AtPtr(offset, currentInstPtr + 1); continue; } - - while (!IsTargetAddress(&targets, currentInstPtr + 1 + clear)) { - clear += AddrLength(currentInstPtr + 1 + clear); - } - if (currentInstPtr + 1 + clear == envPtr->codeNext) { - envPtr->codeNext -= clear; - } else { - while (clear --> 0) { - *(currentInstPtr + 1 + clear) = INST_NOP; - } - } } +} + +/* + * ---------------------------------------------------------------------- + * + * TclOptimizeBytecode -- + * + * A very simple peephole optimizer for bytecode. + * + * ---------------------------------------------------------------------- + */ - Tcl_DeleteHashTable(&targets); +void +TclOptimizeBytecode( + CompileEnv *envPtr) +{ + ConvertZeroEffectToNOP(envPtr); + AdvanceJumps(envPtr); + TrimUnreachable(envPtr); } /* |