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[Bug middle-end/85989] Incorrect result for example involving unary minus in a loop
- From: "rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 30 May 2018 14:32:08 +0000
- Subject: [Bug middle-end/85989] Incorrect result for example involving unary minus in a loop
- Auto-submitted: auto-generated
- References: <bug-85989-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85989
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Status|UNCONFIRMED |NEW
Last reconfirmed| |2018-05-30
CC| |rsandifo at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. It is backprop somehow concluding that the load is never negative:
--- t.i.093t.ccp2 2018-05-30 16:28:48.811740654 +0200
+++ t.i.096t.backprop 2018-05-30 16:28:48.811740654 +0200
@@ -59,13 +59,12 @@
<bb 5> [local count: 286363364]:
_3 = *P5_32(D);
_4 = (int) _3;
- P29_36 = -_4;
b_P5_37 = b_P5_20 + 1;
<bb 6> [local count: 322154758]:
# b_P5_20 = PHI <b_P5_37(5), 0(16)>
# P26_22 = PHI <P29_23(5), 10(16)>
- # P29_23 = PHI <P29_36(5), 10(16)>
+ # P29_23 = PHI <_4(5), 10(16)>
if (b_P5_20 <= 7)
goto <bb 5>; [88.89%]
else