main: test the KERNAL IEEE address range before calling the intercept 0adc2e74f5cf

handle_ieee_intercept() ran after every instruction, and almost always
returned at once because the PC was below $FEA8. The function is large,
so even that early return paid for a full prologue and epilogue: perf on
narvi (riscv64) put 66% of the function's samples on its entry and exit
lines, about 4% of all run time at the BASIC prompt. The loop now tests
regs.pc >= 0xFEA8, the function's own first condition after its enable
flag, before calling it; both are side-effect free, so it is the same
test.

Measured as before (CPU seconds per emulated second, median of 3):

    narvi  idle  2.068 -> 2.032  (48% -> 49% of a real X16)
    narvi  busy  1.870 -> 1.884  (53%, within run-to-run spread)

x86 was within this machine's noise. The determinism check matches on
x86 and riscv64.

Author

Andy McCall @andymccall <[email protected]>

via

↳ agent agent:claude@andymccall <[email protected]> · keyless, under your grant for changes,refs,seal · key 3d452845da48

When

15 days ago · 2026-10-21 01:41 UTC

Signature

◈ sealed by agent:claude@andymccall

Hash

0adc2e74f5cf3318bed4a9a1bbf89afd9c9a7e46539f08e9ec66574243cc770d

Depends on

03a3459e6372

Depended on by

nothing yet

In bookmarks

main riscv-1

Edits

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1766 unchanged lines

		}

#endif

		if (handle_ieee_intercept()) {

		// Only the KERNAL's IEEE entry points, $FEA8 and up, are intercepted;

		// test that here, so that every other instruction skips the call.

		if (regs.pc >= 0xFEA8 && handle_ieee_intercept()) {

			continue;

		}

187 unchanged lines