[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581
--- Comment #1 from David Simcha dsim...@yahoo.com 2011-02-15 11:29:13 PST ---
I think this is actually a long-standing, hard to reproduce, non-deterministic
codegen bug that strikes on 32-bit as well, though due to the non-deterministic
nature of it, under different circumstances. Here's some code that segfaults
on 32 with stock DMD 2.051, only with -O -inline -release enabled. This is
slightly less reduced than the 64 version because anytime I try to reduce it
more, the bug goes away.
import std.stdio;
bool comp(long a, long b) { return a b; }
size_t medianOf3(T)(T[] data) {
// Removing this print statement changes the result.
stderr.writeln(data[0], '\t', data[$ / 2], '\t', data[$ - 1]);
immutable size_t mid = data.length / 2;
immutable uint result = ((cast(uint) (comp(data[0], data[mid]))) 2) |
((cast(uint) (comp(data[0], data[$ - 1]))) 1) |
(cast(uint) (comp(data[mid], data[$ - 1])));
assert(result != 2 result != 5 result 8); // Cases 2, 5 can't
happen.
switch(result) {
case 1: // 001
case 6: // 110
return data.length - 1;
case 3: // 011
case 4: // 100
return 0;
case 0: // 000
case 7: // 111
return mid;
default:
assert(0);
}
assert(0);
}
void main() {
long[] stuff = [4602111750194969114, 4591797823464657051,
4579622497201165564];
medianOf3(stuff);
}
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[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 David Simcha dsim...@yahoo.com changed: What|Removed |Added OS/Version|Windows |Linux --- Comment #2 from David Simcha dsim...@yahoo.com 2011-02-15 11:31:50 PST --- Forgot to mention: The 32-bit version still only segfaults on Linux. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 David Simcha dsim...@yahoo.com changed: What|Removed |Added Platform|x86_64 |All --- Comment #3 from David Simcha dsim...@yahoo.com 2011-02-15 15:59:13 PST --- I did a little bisecting. This issue appeared in 2.050. It's possible that it's been around since before that but requires different magic numbers on earlier releases, though I doubt it because I would have probably noticed the bug if it was around for a long time. I do my day to day work on Windows but use Linux for the occasional computationally intensive project. I haven't done much serious (i.e. Linux-based) computation since 2.050 was released, but I was doing a lot of it earlier on. The function I isolated this test case from was around in its current form back then and was definitely getting called a lot in those projects. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 --- Comment #4 from David Simcha dsim...@yahoo.com 2011-02-15 16:16:59 PST --- Created an attachment (id=913) Diff of 2.049 vs. 2.050 ASM output. One more hint: Here's a diff of the ASM output for the function body of medianOf3 between 2.049 (test49.asm) and 2.050 (test50.asm). The most notable difference is that in 2.050 the comparison function gets inlined. In 2.049 it doesn't. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 --- Comment #5 from David Simcha dsim...@yahoo.com 2011-02-15 17:25:48 PST --- Unfortunately this appears to be a Heisenbug. When I put print statements in to figure out what's going on and call the switch statement function manually, it starts working. However, the one hint I did get from mucking around in switch_.d is that replacing the memcmp() call with a manual for loop and recompiling druntime solves the problem. Not sure if this is due to the Heisenbug nature of this thing or if it indicates that the memcmp() call is the culprit. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 --- Comment #6 from David Simcha dsim...@yahoo.com 2011-02-15 18:10:30 PST --- Ignore the last comment. It was directed to the wrong bug report. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 Walter Bright bugzi...@digitalmars.com changed: What|Removed |Added CC||bugzi...@digitalmars.com --- Comment #7 from Walter Bright bugzi...@digitalmars.com 2011-02-15 21:48:42 PST --- https://github.com/D-Programming-Language/dmd/commit/175bb7540db3ad16655772fe47e4dcbeab7fa380 https://github.com/D-Programming-Language/dmd/commit/cfc773a5bf99b6e636b03644787b71f4acc1c622 This addresses the 64 bit code gen problems, not the 32 bit issue. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 5581] [64-bit] Wrong code with bitwise operations on bools
http://d.puremagic.com/issues/show_bug.cgi?id=5581 Walter Bright bugzi...@digitalmars.com changed: What|Removed |Added Status|NEW |RESOLVED Resolution||FIXED --- Comment #8 from Walter Bright bugzi...@digitalmars.com 2011-02-15 22:39:38 PST --- Fix for 32 bit code (completely different from 64 bit bug): https://github.com/D-Programming-Language/dmd/commit/52879f36cb28b05813161002d559fecc11a0cbe6 https://github.com/D-Programming-Language/dmd/commit/525de3d38d8202a810352e6811328afa19166591 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
