Ah! Got it! The generated code is incorrect! Source:
leadingZeroCount = 0 ifTrue: ["highBit is not defined for negative Integer" self primitiveFail] ifFalse: ["Nice bit trick: 1-based high-bit is (32 - clz) - 1 to account for tag bit. This is like two-complement - clz - 1 on 5 bits, or in other words a bit-invert operation clz ^16r1F" self pop: 1 thenPushInteger: (leadingZeroCount bitXor: (BytesPerWord * 8 - 1))]. ^self].
Generated:
if (leadingZeroCount == 0) {
/* highBit is not defined for negative Integer */ /* begin primitiveFail */ if (!GIV(primFailCode)) { GIV(primFailCode) = 1; } } /* begin pop:thenPushInteger: */ longAtput((sp = GIV(stackPointer) + ((0) * BytesPerWord)), (((usqInt)(leadingZeroCount ^ ((BytesPerWord * 8) - 1)) << 3) | 1)); GIV(stackPointer) = sp;
The ifFalse: branch has been gobbled... Hence with always push (0 bitXor: 16r3F) as small integer in place of the receiver, the fail the primitive... The fallback code proceeds with 16r3F and answers 6... Correct.
WE MUST FIX THE GENERATOR ASAP !
Le ven. 15 janv. 2021 à 03:15, Nicolas Cellier nicolas.cellier.aka.nice@gmail.com a écrit :
Hi all, I got this on uptodate Mingw Win 64 bits Squeak.cog.spur VM:
(1to: 8) collect: [:i|-2942842961920 highBitOfMagnitude] -> #(6 6 42 42 42 42 42 42)
That is correct once jitted, but wrong first two times... I just can't understand when/how it fails by reading the code... Any clue?
Nicolas