Status: New
Owner: ----
New issue 3737 by [email protected]: wrong rounding mode?
https://code.google.com/p/v8/issues/detail?id=3737
Not sure if this is a bug
--- Raw source ---
(x) { return x == Math.floor(x); }
0x51d542e4 36 8b4508 mov eax,[ebp+0x8] ;; debug:
position 76
;;; <@18,#31> double-untag
0x51d542e7 39 a801 test al,0x1
0x51d542e9 41 7414 jz 63 (0x51d542ff)
0x51d542eb 43 8178ff7181f04e cmp [eax-0x1],0x4ef08171 ;; object:
0x4ef08171 <Map(elements=3)>
0x51d542f2 50 0f8567000000 jnz 159 (0x51d5435f)
0x51d542f8 56 f20f104803 movsd xmm1,[eax+0x3]
0x51d542fd 61 eb0b jmp 74 (0x51d5430a)
0x51d542ff 63 89c1 mov ecx,eax
0x51d54301 65 d1f9 sar ecx,1
0x51d54303 67 0f57c9 xorps xmm1,xmm1
0x51d54306 70 f20f2ac9 cvtsi2sd xmm1,ecx
;;; <@20,#15> math-floor
0x51d5430a 74 0f57c0 xorps xmm0,xmm0
0x51d5430d 77 660f2ec8 ucomisd xmm1,xmm0
0x51d54311 81 750d jnz 96 (0x51d54320)
0x51d54313 83 660f50c9 movmskpd ecx,xmm1
0x51d54317 87 f6c101 test_b cl,0x1
0x51d5431a 90 0f8544000000 jnz 164 (0x51d54364)
0x51d54320 96 660f3a0bc109 roundsd xmm0,xmm1,9
By my reading of the intel specs, this has an immediate byte operand (9 =
0b1001) specifying P=1, O=0, RC=01
The 'O' field is '0', selecting the MSCSR:RC, but I think it should be '1',
selecting the immediate RC field.
Rounding control source definitions:
Value Description
0 MXCSR:RC
1 Use RC field value.
Should the field be 0b1101 ?
0x51d54326 102 f20f2cc8 cvttsd2si ecx,xmm0
0x51d5432a 106 83f901 cmp ecx,0x1
0x51d5432d 109 0f8031000000 jo 164 (0x51d54364)
;;; <@22,#32> int32-to-double
0x51d54333 115 0f57d2 xorps xmm2,xmm2
0x51d54336 118 f20f2ad1 cvtsi2sd xmm2,ecx
;;; <@25,#16> compare-numeric-and-branch
0x51d5433a 122 660f2eca ucomisd xmm1,xmm2
0x51d5433e 126 0f8a06000000 jpe 138 (0x51d5434a)
0x51d54344 132 0f840a000000 jz 148 (0x51d54354)
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