Displaying 6 results from an estimated 6 matches for "binomialcoefficient".
2009 Oct 13
1
[LLVMdev] 65bit integer math
...prit here so I can disable it in this
> > situation.
>
> I'm pretty sure this is the fault of one of the loop passes (I forget
> which one off the top of my head).
It's SCEV. I have this very bit of code disabled in our tree for exactly the
reasons Micah gives. Check out BinomialCoefficient is ScalarEvolution.cpp.
Here's the big hack we put in, which is just the code that used to be there
in 2.3:
// We need at least W + T bits for the multiplication step
// FIXME: A temporary hack; we round up the bitwidths
// to the nearest power of 2 to be nice to the code generator.
u...
2008 Dec 04
0
[LLVMdev] 32bit math being promoted to 64 bit
instcombine doesn't seem to be doing it. From my testing it seems to
only occur when I use -indvars after a long string of commands.
For example:
llvm-as < test_fc_27.ll | opt -preverify -domtree -verify
-lowersetjmp -raiseallocs -simplifycfg -domtree -domfrontier
-mem2reg -globalopt -globaldce -ipconstprop -deadargelim
-instcombine -simplifycfg -ba
siccg -prune-eh -inline
2009 Oct 13
0
[LLVMdev] 65bit integer math
On Mon, Oct 12, 2009 at 6:15 PM, Villmow, Micah <Micah.Villmow at amd.com> wrote:
> I have a test case(attached as fc_long.ll) that when run through the
> optimizer produces 65bit integer math(fc_long-opt.ll).
>
>
>
> Now I understand that llvm can have any length integer, but I consider
> turning a 64bit mul into multiple 65 bit instructions to be a ‘bad’
>
2008 Dec 04
2
[LLVMdev] 32bit math being promoted to 64 bit
On Thu, Dec 4, 2008 at 7:08 PM, Chris Lattner <clattner at apple.com> wrote:
>
> On Dec 4, 2008, at 8:58 AM, Villmow, Micah wrote:
>
> What optimization pass promotes 32 bit math operations to 64 bit operations
> so I can disable it? I have code that works fine with optimizations turned
> off but fails with it turned on because of this stage.
>
>
> Do you have a
2010 Nov 23
2
[LLVMdev] Unrolling power sum calculations into constant time expressions
Hello,
I noticed that feeding 'clang -O3' with functions like:
int sum1(int x) {
int ret = 0;
for(int i = 0; i < x; i++)
ret += i;
return ret;
}
int sum2(int x) {
int ret = 0;
for(int i = 0; i < x; i++)
ret += i*i;
return ret;
}
...
int sum20(int x) {
int ret = 0;
for(int i = 0; i < x; i++)
ret +=
2009 Oct 13
4
[LLVMdev] 65bit integer math
I have a test case(attached as fc_long.ll) that when run through the
optimizer produces 65bit integer math(fc_long-opt.ll).
Now I understand that llvm can have any length integer, but I consider
turning a 64bit mul into multiple 65 bit instructions to be a 'bad'
optimization. This eventually expands to a 128bit multiply
call(__multi3) which I have absolutely no interest in supporting.