Mar 22, 2026
diff --git a/Include/internal/pycore_optimizer.h b/Include/internal/pycore_optimizer.h
 returntrace->next-1;
 }

 staticinlinebool
 uop_buffer_rewind(_PyJitUopBuffer*trace)
 {
 if (trace->next <=trace->start) {
 return false;
   }
 trace->next--;
 return true;
 }

 staticinlineint
 uop_buffer_length(_PyJitUopBuffer*trace)
 {
diff --git a/Python/optimizer_analysis.c b/Python/optimizer_analysis.c
    _PyUOpInstruction *this_instr = NULL;
    JitOptRef *stack_pointer = ctx->frame->stack_pointer;

    for (int i = 0; i < trace_len; i++) {
    int i = 0;
    for (; i < trace_len && !ctx->done; i++) {
        this_instr = &trace[i];
        if (ctx->done) {
            // Don't do any more optimization, but
            // we still need to reach a terminator for corrctness.
            *(ctx->out_buffer.next++) = *this_instr;
            if (is_terminator_uop(this_instr)) {
                break;
            }
            continue;
        }

        int oparg = this_instr->oparg;
        opcode = this_instr->opcode;
            assert(STACK_LEVEL() >= 0);
        }
    }
    if (ctx->out_of_space) {
        DPRINTF(3, "\n");
        DPRINTF(1, "Out of space in abstract interpreter\n");
    }
    if (ctx->contradiction) {
        // Attempted to push a "bottom" (contradiction) symbol onto the stack.
        // This means that the abstract interpreter has optimized to trace
        OPT_STAT_INC(optimizer_contradiction);
        return 0;
    }
    if (ctx->out_of_space) {
        DPRINTF(3, "\n");
        DPRINTF(1, "Out of space in abstract interpreter at length %d\n",
            uop_buffer_length(&ctx->out_buffer));
        // Rewind to previous instruction and replace with _EXIT_TRACE.
        _PyUOpInstruction *curr = uop_buffer_last(&ctx->out_buffer);
        while (curr->opcode != _SET_IP) {
            if (!uop_buffer_rewind(&ctx->out_buffer)) {
                // Reached the start.
                return 0;
            }
            curr = uop_buffer_last(&ctx->out_buffer);
        }
        assert(curr->opcode == _SET_IP);
        int32_t old_target = (int32_t)uop_get_target(curr);
        curr->opcode = _EXIT_TRACE;
        curr->format = UOP_FORMAT_TARGET;
        curr->target = old_target;
        DPRINTF(1, "Rewound to length %d\n", uop_buffer_length(&ctx->out_buffer));
    }
    else {
        // Don't do any more optimization, but
        // we still need to reach a terminator for correctness.
        while (!is_terminator_uop(uop_buffer_last(&ctx->out_buffer))) {
            this_instr = &trace[i];
            *(ctx->out_buffer.next++) = *this_instr;
            i++;
        }
    }

    /* Either reached the end or cannot optimize further, but there
     * would be no benefit in retrying later */
Original file line number	Diff line number	Diff line change
Expand Up		@@ -67,6 +67,16 @@ uop_buffer_last(_PyJitUopBuffer *trace)
		returntrace->next-1;
		}

		staticinlinebool
		uop_buffer_rewind(_PyJitUopBuffer*trace)
		{
		if (trace->next <=trace->start) {
		return false;
		}
		trace->next--;
		return true;
		}

		staticinlineint
		uop_buffer_length(_PyJitUopBuffer*trace)
		{
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -488,17 +488,9 @@ optimize_uops(
		_PyUOpInstruction *this_instr = NULL;
		JitOptRef *stack_pointer = ctx->frame->stack_pointer;

		for (int i = 0; i < trace_len; i++) {
		int i = 0;
		for (; i < trace_len && !ctx->done; i++) {
		this_instr = &trace[i];
		if (ctx->done) {
		// Don't do any more optimization, but
		// we still need to reach a terminator for corrctness.
		(ctx->out_buffer.next++) = this_instr;
		if (is_terminator_uop(this_instr)) {
		break;
		}
		continue;
		}

		int oparg = this_instr->oparg;
		opcode = this_instr->opcode;
Expand DownExpand Up		@@ -531,10 +523,6 @@ optimize_uops(
		assert(STACK_LEVEL() >= 0);
		}
		}
		if (ctx->out_of_space) {
		DPRINTF(3, "\n");
		DPRINTF(1, "Out of space in abstract interpreter\n");
		}
		if (ctx->contradiction) {
		// Attempted to push a "bottom" (contradiction) symbol onto the stack.
		// This means that the abstract interpreter has optimized to trace
Expand All		@@ -548,6 +536,35 @@ optimize_uops(
		OPT_STAT_INC(optimizer_contradiction);
		return 0;
		}
		if (ctx->out_of_space) {
		DPRINTF(3, "\n");
		DPRINTF(1, "Out of space in abstract interpreter at length %d\n",
		uop_buffer_length(&ctx->out_buffer));
		// Rewind to previous instruction and replace with _EXIT_TRACE.
		_PyUOpInstruction *curr = uop_buffer_last(&ctx->out_buffer);
		while (curr->opcode != _SET_IP) {
		if (!uop_buffer_rewind(&ctx->out_buffer)) {
		// Reached the start.
		return 0;
		}
		curr = uop_buffer_last(&ctx->out_buffer);
		}
		assert(curr->opcode == _SET_IP);
		int32_t old_target = (int32_t)uop_get_target(curr);
		curr->opcode = _EXIT_TRACE;
		curr->format = UOP_FORMAT_TARGET;
		curr->target = old_target;
		DPRINTF(1, "Rewound to length %d\n", uop_buffer_length(&ctx->out_buffer));
		}
		else {
		// Don't do any more optimization, but
		// we still need to reach a terminator for correctness.
		while (!is_terminator_uop(uop_buffer_last(&ctx->out_buffer))) {
		this_instr = &trace[i];
		(ctx->out_buffer.next++) = this_instr;
		i++;
		}
		}

		/* Either reached the end or cannot optimize further, but there
		* would be no benefit in retrying later */
Expand Down