similar to: [LLVMdev] why gvn does not work for global variables

Hi, Assume I have the following code. The first four instructions in each BB does the same thing. So I think GVN() can remove the redundant code. However, after I apply GVN to my module by "Passes.add(createGVNPass())" and "Passes.run(*myModule)". It seems GVN does not remove the redundant instructions. Can anyone give me a hint what's going on here? Any hint is

On May 3, 2011, at 3:25 PM, Arushi Aggarwal wrote: > Hi, > > GVN seems to be running in an infinite loop on my example. I have attached the output of one iteration. I cant seem to reduce the testcase either. > > Any pointers to how to reduce the test case. Bugzilla can reduce testcases that cause infinite loops (it has a -timeout flag), I'd try it. Even if this doesn't

Hi, GVN seems to be running in an infinite loop on my example. I have attached the output of one iteration. I cant seem to reduce the testcase either. Any pointers to how to reduce the test case. THanks, Arushi GVN iteration: 8 GVN WIDENED LOAD: %0 = load i8* getelementptr inbounds (%struct.CHESS_POSITION* @search, i64 0, i32 23), align 2, !dbg !875 TO: %1 = load i16* bitcast (i8*

Hello, I found that GVN doesn't promote identical sequence of instructions in if and else branch to their common predecessors. For example, for the following code snippet pred: … br i1 %cmp, label %if, label %else if: %incdec.ptr.1 = getelementptr inbounds i8, i8* %ptr, i64 1 %cast1 = ptrtoint i8* %incdec.ptr.1 to i64 … else: %incdec.ptr.2 = getelementptr inbounds i8, i8* %ptr,

There is a phi-node "%phi = phi i64 [%cast1, %if], [%cast2, %else]" in the common successor. The actual control flow is a bit more complex, but there is a common successor block, and %cast1 and %cast2 are the two values that the phi node in the common successor takes. Does the existence of the phi node affect optimization? Thanks, Taewook From: <mats.o.petersson at

On 24 February 2015 at 02:05, Chandler Carruth <chandlerc at google.com> wrote: > Will try to reply to the larger thread again soon, but a quick reply on a > bit of a tangent... > > On Mon, Feb 23, 2015 at 8:45 PM, Hal Finkel <hfinkel at anl.gov> wrote: >> >> 2. Should unreachable code be allowed to contain nonsense (like >> instructions that depend on

and by "right thing" i mean it can hoist if you want and it can prove it will not extend the live range. Note that VBE (very busy expressions) is a code size optimization only. It does not save time. On Tue, Feb 9, 2016 at 12:26 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > This GVN does not do that, this is correct. It is a very simple GVN. All > phi nodes are

Hello to whom this may concern, Versioned this as I saw identical title before. I'm compiling a clang project where I'm seeing GVN mess up and replace a load with a wrong def value. I am using LLVM-3.5, but the problem has been observed upto 3.8. To illustrate the problem, define i32 @main scalar.ph: <initialize [80 x i16] %dest> ... preheader: %index=0 br test, loop1, bb2

Thanks for quick reply Daniel, I tried to make a simple C testcase, but could not reproduce the same condition with output from Clang. I suppose I could modify the C code to make it look similar with TBAA's; I may be able to provide this by eod. > store %ptr above the load. My mistake; I was referring to the store $lcssa in bb2. Looking at the C source code, it should definitely alias

before inlining all 20005 after inlining somewhere here changed made it NoAlias after Global Variable Optimizer 20014 20373 20255 20372 20254 before GVN 19993 20011 19991 20010 20030 It appears that TBAA metadata certainly changed after inlining and subsequent passes. I have attached the .bc file. I think I will try to dump out more TBAA metadata between passes. The method in

Hi, i have the following code: define internal %"struct.dexter::ConditionConstant"* @_ZN6dexter18BinaryConditionAdd8evaluateEv5(%"class.dexter::BinaryConditionAdd"*) { entry: %1 = getelementptr inbounds %"class.dexter::BinaryConditionAdd"* %0, i32 0, i32 0, i32 1 %2 = load %"class.dexter::BaseCondition"** %1, align 8 %3 = bitcast

> Maybe. > My view is the ideal is either no-unreachable code, or unreachable blocks > only contain terminators. I am definitely happy with both. What worries me is introducing a special dominance rule for unreachable blocks. >> I don't think that rejecting >> >> %a = getelementptr inbounds i8* %a, i64 1 >> >> but accepting >> >> %a =

Hi, I'm having a problem with GVN removing a load instruction that I think is needed. Dump before GVN: *** IR Dump Before Global Value Numbering *** ; Function Attrs: minsize optsize define i16 @TEST__MAIN(i16 %argc.13.par, i16** %argv.14.par) #0 { %buf.17 = alloca [10 x i16], align 1 %_tmp30 = getelementptr inbounds [10 x i16], [10 x i16]* %buf.17, i16 0, i16 0, !dbg !22 call

On 02/25/2015 10:41 AM, Rafael Espíndola wrote: >>> all the zero paths from entry to %a pass by %b. >> >> That is a graph-wise definition, sure. >> So, this is an interesting definition, and maybe this is part of the source >> of the problem. >> >> For SSA, at least GCC requires that both "definition block dominates use >> block" (which

>> all the zero paths from entry to %a pass by %b. > > > That is a graph-wise definition, sure. > So, this is an interesting definition, and maybe this is part of the source > of the problem. > > For SSA, at least GCC requires that both "definition block dominates use > block" (which would be true here), *and* > that "definition appears before use in

Many thanks for the pointer! I missed that bug report since the title was about GVN. If there's interest in supporting this feature I can help since we've formalized most of BasicAA. I can easily verify if proposed changes are correct. (I'll release the code soon). Nuno Quoting Björn Pettersson A <bjorn.a.pettersson at ericsson.com>: > Hi Nuno. > I can't

Mainline. ------------------------------ From: John Criswell Sent: Tuesday, May 03, 2011 8:34 PM To: Arushi Aggarwal Cc: LLVM Dev Subject: Re: [LLVMdev] GVN Infinite loop On 5/3/11 5:25 PM, Arushi Aggarwal wrote: Hi, GVN seems to be running in an infinite loop on my example. I have attached the output of one iteration. I cant seem to reduce the testcase either. Are you running with LLVM

Thanks for your point that out. I just add DataLayout in my code such as "mod->setDataLayout("e-m:e-i64:64-f80:128-n8:16:32:64-S128");", still no luck. I'm really confused about this. Do I need to add more passes before -loop-unroll? On Sat, Aug 22, 2015 at 11:36 AM, Mehdi Amini <mehdi.amini at apple.com> wrote: > > On Aug 22, 2015, at 7:27 AM, Xiangyang

On 25 February 2015 at 10:58, Daniel Berlin <dberlin at dberlin.org> wrote: > > > On Wed, Feb 25, 2015 at 6:26 AM, Rafael Espíndola > <rafael.espindola at gmail.com> wrote: >> >> > Maybe. >> > My view is the ideal is either no-unreachable code, or unreachable >> > blocks >> > only contain terminators. >> >> I am

Hello everyone, I think I have found an gvn / alias analysis related bug, but before opening an issue on the tracker I wanted to see if I am missing something. I have the following testcase: define spir_kernel void @test(<2 x i32*> %in1, <2 x i32*> %in2, i32* %out) { > entry: > ; Just some temporary storage > %tmp.0 = alloca i32 > %tmp.1 = alloca i32 > %tmp.i =