similar to: [LLVMdev] 64-bit Attributes?

Hi Kostya, > Today, llvm/Attributes.h defines 'Attributes' as 'unsigned'. > This bit vector is fully packed, and I am probably not the only one who wants to > add bits to it. > Is there a strong reason not to define Attributes as uint64_t? > At first glance this seems doable, and the IR reader/writer will not need to be > changed at all (or at least, not

Hi Kostya, One unexpected piece of fallout in your recent attributes change (r148553) was that it introduced a bunch of static constructors into .o files that #include Attributes.h, due to stuff like this: const Attributes None (0); ///< No attributes have been set const Attributes ZExt (1<<0); ///< Zero extended before/after call const Attributes SExt

I see the problem. Let me try to come up with a solution that does not involve constructors but also does not sacrifice type safety. On Tue, Feb 7, 2012 at 12:01 PM, Chris Lattner <clattner at apple.com> wrote: > Hi Kostya, > > One unexpected piece of fallout in your recent attributes change (r148553) > was that it introduced a bunch of static constructors into .o files that

Hi Alexandre, On Wed, Oct 19, 2016 at 6:27 PM, Alexandre Isoard <alexandre.isoard at gmail.com> wrote: > Really interesting read. I am perplexed now, and am not even sure what is > the meaning of undef anymore. Welcome aboard. :) > Example (unrelated to your blog post, but still weird): > %x = sext i1 undef to i2 > > I understand that I can replace it by either of: >

In https://reviews.llvm.org/D68103 the InstCombine learned that shift-by-sext is simply a shift-by-zext. But the transform is limited to single-use sext. We can quite trivially get a case where there are two shifts by the same sext: https://godbolt.org/z/j6mO3t <- We should handle those cases. In https://reviews.llvm.org/D68103#1686130 Sanjay Patel notes that this sext is intrusive for

I have another round of questions about IR select canonicalizations. For the purity of this quiz, please disregard prior knowledge of how this is handled by instcombine or how this is lowered by your favorite target...of course we'll fix it. :) Some answers in the links below if you do want to know. Which, if any, of these is canonical? 1. Is a zext simpler than a select? a. define i32

Thanks for taking a look! On Tue, Oct 1, 2019 at 9:09 PM Philip Reames <listmail at philipreames.com> wrote: > On 9/27/19 1:40 PM, Roman Lebedev via llvm-dev wrote: > > In https://reviews.llvm.org/D68103 the InstCombine learned that shift-by-sext > > is simply a shift-by-zext. > > Just to make sure I'm following, the reasoning here is that the shift > amount must

Hi, This is somewhat similar to the previous thread regarding missed vectorization opportunities (http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-April/084765.html), but maybe different enough to require a new thread. I'm seeing some missed vectorization opportunities in the loop vectorizer because SCEV is not able to fold sext/zext expressions into recurrence expressions (AddRecExpr). This

The thing is, we *don't* "not demand" those high bits. We *don't* not care what's in those bits - IR shifts don't mask their shift amounts. I.e we can't replace `x >> (32-y)` with `x >> (-y)`, which would be legal transform should we not demand those bits. We very much demand them. We just know those bits to be zero. And i'm not sure how to convey

On Mon, Oct 7, 2019 at 11:32 AM Roman Lebedev <lebedev.ri at gmail.com> wrote: > > Bump. Any further thoughts here? > > To recap - i don't really see how this can be a demandedbits problem - we do > demand all those bits, we just know they must be zero. > (i would love to be proven wrong though!) > > Roman. > > On Tue, Oct 1, 2019 at 11:17 PM Roman Lebedev

For void test0(unsigned short a, unsigned short * in, unsigned short * out) { for (unsigned short w = 1; w < a - 1; w++) //this will never overflow out[w] = in[w+7] * 2; } I think it will be sufficient to add a couple of new cases to ScalarEvolution::HowManyLessThans -- zext(A) ult zext(B) == A ult B sext(A) slt sext(B) == A slt B Currently it bails out if it sees a non-add

On Nov 12, 2009, at 7:35 PM, Talin wrote: > On Thu, Nov 12, 2009 at 5:58 PM, Chris Lattner <clattner at apple.com> > wrote: > > There is also the issue of how constants should be represented. > > For all current processors that I know of, an intptr will be either > 32 or 64 bits. However, there may be some future processor which > supports 128-bit pointers

Chris Lattner wrote: > On Nov 12, 2009, at 7:35 PM, Talin wrote: >> On Thu, Nov 12, 2009 at 5:58 PM, Chris Lattner <clattner at apple.com >> <mailto:clattner at apple.com>> wrote: >> >> >> There is also the issue of how constants should be represented. >> >> For all current processors that I know of, an intptr will be either >> 32 or

Hi Mehdi, On Wed, Oct 19, 2016 at 8:29 PM, Mehdi Amini <mehdi.amini at apple.com> wrote: >> sext(x): >> t = zext x >> result = 0 >> for i = 0 to bitwidth: >> result |= t << i; >> return result > > I don’t understand this definition of sext? > Are you trying to express that we will copy the sign one bit at a time, and so every `new`

Hi, I have a question about the "sext..to" instruction. In the document, I found two examples: %x = sext i8 -1 to i16 It means: i8 -1 = 1111 1111 --> 1111 1111 1111 1111 = i16 how can it determinate, that the i16 value %x positive is (65535)? And the second example: %y = sext i1 true to i32 1 --> 1111 1111 1111 1111 1111 1111 1111 1111 In this example, %y is -1 I'm not sure

On Nov 12, 2009, at 11:29 PM, John McCall wrote: >> sext/zext/trunc are very nice for the optimizer, we should keep >> them. It means that the optimizer doesn't have to check that the >> input to a sext is bigger or smaller than the result, for example. >> Code that cares (e.g. instcombine) really likes this. > > We could just say that code has undefined

> Of course, and the point is that, for example, on x86_64, the zext here is free. I'm still trying to understand the problem... > > In the example you provided in your previous e-mail, we choose the solution: > > `GEP @Global, zext(V)` -> `GEP (@Global + zext VStart), {i64 0,+,1}` > `V` -> `trunc({i64 0,+,1}) + VStart` > > instead of the actually-better

In my language there are a lot of i16 definitions, but almost all of the time they are upgraded to i32 because my add operations only happen on i32. So to be representative to my language definition, I have a lots of Sext/Zext and Truncs pretty much every time I add or subtract. As soon as I pass through InstCombine things look much nicer, all the upcasts and downcasts go away, but my test cases

Hi Sanjoy, Thank you for looking into this! Yes, your patch does fix my larger test case too. My algorithm gets double performance improvement with the patch, as the loop now has a smaller instruction set and succeeds to unroll w/o any extra #pragma's. I also ran the LLVM tests against the patch. There are 6 new failures: Analysis/LoopAccessAnalysis/number-of-memchecks.ll

I'm looking at the output of memcmp() expansion (D34904), and I noticed that there are many ways to produce the common positive/zero/negative comparison result in IR. For the following 6 functionally equivalent C source functions, we produce 6 different versions of IR which leads to 6 different asm outputs for x86. Which of these should we choose as canonical IR form? 1. Two selects int