similar to: Optimization Problem

My general feeling is this: No optimizations should be creating int2ptr/ptr2int. We really need to fix them all. They should use pointer casts and i8* GEPs. This has, unfortunately, been a problem for a long time. As Johannes says, optimizing int2ptr/ptr2int is very tricky. In part, becaue all dependencies, including implicit control dependencies, end up being part of the resulting aliasing

Hi all, We noticed a lot of unnecessary ptrtoint instructions that stand in way of some of our optimizations; the code pattern looks like this: bb1: %int1 = ptrtoint %struct.s* %ptr1 to i64 bb2: %int2 = ptrtoint %struct.s* %ptr2 to i64 %bb3: %phi.node = phi i64 [ %int1, %bb1 ], [%int2, %bb2 ] %ptr = inttoptr i64 %phi.node to %struct.s* In short, the pattern above arises due to: 1.

On 06/20/2017 03:26 AM, Hal Finkel wrote: > Hi, Adrien, Hello Hal! Thanks for your answer! > Thanks for reporting this. I recommend that you file a bug report at > https://bugs.llvm.org/ Will do! > Whenever I see reports of missed optimization opportunities in the face > of ptrtoint/inttoptr, my first question is: why are these instructions > present in the first place? At

LLVM 2.7's ScalarEvolution.cpp has this scary comment: // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can // lead to pointer expressions which cannot safely be expanded to GEPs, // because ScalarEvolution doesn't respect the GEP aliasing rules when // simplifying integer expressions. I think I understand what the comment is saying. If a GEP has

RFC: GEP as canonical form for pointer addressing I would like to propose that we designate GEPs as the canonical form for pointer addressing in LLVM IR before CodeGenPrepare. Corollaries 1) It is legal for an optimizer to convert inttoptr+arithmetic+inttoptr sequences to GEPs, but not vice versa. 2) Input IR which does not contain inttoptr instructions will never contain inttoptr

Hi, I am observing some incorrect behavior in basicaa, wherein two pointers that basicaa should determine to be MustAlias are ending up NoAlias - the other extreme :( I am blaming this on basicaa not handling inttoptr. Here is the relevant IR snippet. -------------------- %sunkaddr36 = ptrtoint %struct.BitParams* %bs to i32 %sunkaddr37 = add i32 %sunkaddr36, 16 %sunkaddr38 = inttoptr i32

Thank you for the hint. I adjusted the code and it works: The code after replacing inttoptr with getelementptr: define { i32, i32, i8* } @test(i32 %foo, i32 %bar, i8* %sp) { entry: ; push foo (On "stack") %sp_1 = getelementptr i8, i8* %sp, i32 -4 %sp_1_ptr = bitcast i8* %sp_1 to i32* store i32 %foo, i32* %sp_1_ptr, align 4 ; push bar %sp_2 = getelementptr i8, i8* %sp_1,

Hello all, There is a missing vectorization opportunity issue with clang 4.0 with the file attached. Indeed, when compiled with -O2, the "op_distance" function get vectorized, but not the "op" one. For information, this test case has been reduced from a file generated by the Pythran compiler (https://github.com/serge-sans-paille/pythran). If we take a look at the generated

Hi again. I have a complex type system in my custom language that isn't easily representable as LLVM IR types, so I figured I could mostly get along with treating my types as i8* and doing the appropriate bitcasts and inttoptr instructions, and doing pointer arithmetic myself (by casting the pointers to ints, adding the appropriate byte offsets, and then casting back to pointers). However,

I have a question about when we should apply these pointer aliasing rules. Do the rules tell us when a load/store is safe? "Any memory access must be done through a pointer value associated with an address range of the memory access, otherwise the behavior is undefined." So this means the conversion discussed here is still safe in terms of memory safety, but its meaning after conversion

Hi again, So I finally gave up on trying to get through the converting (x86' push pop mov add) because it deals a lot with crazy pointer arithmetics and sonce inttoptr and ptrtoint doesn't provide any alias analysis information. Daniel, you said it doesn't make much sense to provide it but in my cases it is actually very much needed, you didn't say it wasn't possible to

On 4/4/2011 6:45 PM, Eli Friedman wrote: > On Mon, Apr 4, 2011 at 5:02 PM, Arushi Aggarwal<arushi987 at gmail.com> wrote: >> >>> Hi, >>> Is it correct to convert, >>> %196 = load i32* %195, align 8 ;<i32> [#uses=1] >>> %197 = zext i32 %196 to i64 ;<i64> [#uses=1] >>> %198 =

On Wed, Apr 20, 2011 at 12:20 PM, Eli Friedman <eli.friedman at gmail.com> wrote: > On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: >> I have a question about when we should apply these pointer aliasing >> rules. Do the rules tell us when a load/store is safe? >> "Any memory access must be done through a pointer value

Hello, I am trying to emulate the "stack" as like on x86 when using push/pop so afterwards I can use LLVM's optimizer passes to simplify (reduce junk) the code. The LLVM IR code: define { i32, i32, i32 } @test(i32 %foo, i32 %bar, i32 %sp) { ; push foo (On "stack") %sp_1 = sub i32 %sp, 4 %sp_1_ptr = inttoptr i32 %sp_1 to i32* store i32 %foo, i32* %sp_1_ptr, align

On Sep 13, 2012, at 12:00 PM, Mon Ping Wang <monping at apple.com> wrote: >>> In C, integer to point conversions are implementation defined and >>> depends on what the addressing structure of the execution environment >>> is. Given the current definition of ptrtoint and intoptr, I feel that >>> the addressing structure feels like a flat memory model

On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: > I have a question about when we should apply these pointer aliasing > rules. Do the rules tell us when a load/store is safe? > "Any memory access must be done through a pointer value associated > with an address range of the memory access, otherwise the behavior is > undefined." >

On 15 Feb 2014, at 23:55, Andrew Trick <atrick at apple.com> wrote: > On Feb 14, 2014, at 5:18 PM, Philip Reames <listmail at philipreames.com> wrote: > >> RFC: GEP as canonical form for pointer addressing >> >> I would like to propose that we designate GEPs as the canonical form for pointer addressing in LLVM IR before CodeGenPrepare. >> >>

Thanks for the answers. Although I am not sure if I've understood the docs about how inttoptr/ptrtointr are different when compared to gep. It says: "It’s invalid to take a GEP from one object, address into a different separately allocated object, and dereference it.". To go back to my intention why I am doing this, I would like to "emulate" some x86 instructions with

Hello all, This is a proposal for reducing # of ptrtoint/inttoptr casts which are not written by programmers but rather generated by LLVM passes. Currently the majority of ptrtoint/inttoptr casts are generated by LLVM; when compiling SPEC 2017 with LLVM r348082 (Dec 2 2018) with -O3, the output IR contains 22,771 inttoptr instructions. However, when compiling it with -O0, there are only 1048

On Mon, Apr 4, 2011 at 5:02 PM, Arushi Aggarwal <arushi987 at gmail.com> wrote: > > >> Hi, >> Is it correct to convert, >>   %196 = load i32* %195, align 8                  ; <i32> [#uses=1] >>   %197 = zext i32 %196 to i64                     ; <i64> [#uses=1] >>   %198 = ptrtoint i8* %193 to i64                 ; <i64> [#uses=1]