diff options
| -rw-r--r-- | Python/ceval.c | 41 |
1 files changed, 35 insertions, 6 deletions
diff --git a/Python/ceval.c b/Python/ceval.c index 324008d..384bfbe 100644 --- a/Python/ceval.c +++ b/Python/ceval.c @@ -602,6 +602,26 @@ eval_frame(PyFrameObject *f) #define JUMPTO(x) (next_instr = first_instr + (x)) #define JUMPBY(x) (next_instr += (x)) +/* OpCode prediction macros + Some opcodes tend to come in pairs thus making it possible to predict + the second code when the first is run. For example, COMPARE_OP is often + followed by JUMP_IF_FALSE or JUMP_IF_TRUE. And, those opcodes are often + followed by a POP_TOP. + + Verifying the prediction costs a single high-speed test of register + variable against a constant. If the pairing was good, then the odds + processor has a high likelihood of making its own successful branch + prediction which results in a nearly zero overhead transition to the + next opcode. + + A successful prediction saves a trip through the eval-loop including + its two unpredictable branches, the HASARG test and the switch-case. +*/ + +#define PREDICT(op) if (*next_instr == op) goto PRED_##op +#define PREDICTED(op) PRED_##op: next_instr++ +#define PREDICTED_WITH_ARG(op) PRED_##op: oparg = (next_instr += 3, (next_instr[-1]<<8) + next_instr[-2]) + /* Stack manipulation macros */ #define STACK_LEVEL() (stack_pointer - f->f_valuestack) @@ -873,6 +893,7 @@ eval_frame(PyFrameObject *f) SETLOCAL(oparg, v); goto fast_next_opcode; + PREDICTED(POP_TOP); case POP_TOP: v = POP(); Py_DECREF(v); @@ -920,7 +941,7 @@ eval_frame(PyFrameObject *f) STACKADJ(2); SET_TOP(x); SET_SECOND(w); - continue; + goto fast_next_opcode; } else if (oparg == 3) { x = TOP(); Py_INCREF(x); @@ -932,7 +953,7 @@ eval_frame(PyFrameObject *f) SET_TOP(x); SET_SECOND(w); SET_THIRD(v); - continue; + goto fast_next_opcode; } Py_FatalError("invalid argument to DUP_TOPX" " (bytecode corruption?)"); @@ -1918,8 +1939,10 @@ eval_frame(PyFrameObject *f) Py_DECREF(v); Py_DECREF(w); SET_TOP(x); - if (x != NULL) continue; - break; + if (x == NULL) break; + PREDICT(JUMP_IF_FALSE); + PREDICT(JUMP_IF_TRUE); + continue; case IMPORT_NAME: w = GETITEM(names, oparg); @@ -1974,10 +1997,13 @@ eval_frame(PyFrameObject *f) JUMPBY(oparg); goto fast_next_opcode; + PREDICTED_WITH_ARG(JUMP_IF_FALSE); case JUMP_IF_FALSE: w = TOP(); - if (w == Py_True) + if (w == Py_True) { + PREDICT(POP_TOP); goto fast_next_opcode; + } if (w == Py_False) { JUMPBY(oparg); goto fast_next_opcode; @@ -1991,10 +2017,13 @@ eval_frame(PyFrameObject *f) break; continue; + PREDICTED_WITH_ARG(JUMP_IF_TRUE); case JUMP_IF_TRUE: w = TOP(); - if (w == Py_False) + if (w == Py_False) { + PREDICT(POP_TOP); goto fast_next_opcode; + } if (w == Py_True) { JUMPBY(oparg); goto fast_next_opcode; |