similar to: is this a bug in an optimization pass?

Hello, I'm working on using the LLVM JIT for a little project of mine, amazing work first off! I have a question about optimization passes. I initially have this function I've created, in python it looks like this: OS_end = 50OS_start = 0OS_timestep = 1birth_rate = .3population = 30.0for time in range(OS_start, OS_end, OS_timestep): births = birth_rate * population deaths = 0.1

Our frontend can guarantee that loads from globals are rematerializable and do not alias with any stores in any function in the given module. We'd like the optimization passes (and ideally the register allocator as well) to be able to use this fact. The globals are not constant "forever" but are constant during the calling of any given function in the module. There seem to

I'm going to show the same function, first normally, and then as a coroutine, and show how gdb can see the variable when it's a normal function, but not when it's a coroutine. I'd like to understand if this can be improved. I'm trying to debug a real world problem, but the lack of debug info on variables in coroutines is making it difficult. Should I file a bug? Is this a

Hi, I have the below test case. --snip-- struct st { int a; int b; }; int * ptr; int x,y; void bar(int *x); void foo() { struct st obj; bar(&obj.b); if(x) obj.a =x; else obj.a =y; for (int i=0; i<obj.a;i++) ptr[i]=i; } --snip-- LLVM IR produced at -O3 is shown below. ref: https://godbolt.org/z/WPlmfr --Snip-- %8 = getelementptr inbounds %struct.st,

> That makes sense, and I think for "direct" values in your definition it is true that all direct values are r-values. > Why do we need DW_OP_LLVM_direct when we already have DW_OP_LLVM_stack_value? Can you give an example of something that is definitely not a stack value, but direct? The difference in definition is the intention: DW_OP_LLVM_direct means "we'd like this

Hi Adrian & Stephen, One thought here: But — not all memory locations are l-values. If we have a DWARF location list for variable "x" which points to a memory address for the first n instructions and the switches to a constant for the remainder of the scope, the memory address is not guaranteed to be an l-value, because writing the the memory address cannot affect the later part of

Below is attached a full IR module that can reproduce this issue, but the part to notice is this: %Foo96Bits = type <{ i24, i24, i24, i24 }> define internal fastcc i16 @main.0.1() unnamed_addr #2 !dbg !113 { Entry: %value = alloca %Foo96Bits, align 1 %b = alloca i24, align 4 %0 = bitcast %Foo96Bits* %value to i8*, !dbg !129 call void @llvm.memcpy.p0i8.p0i8.i64(i8* %0, i8* bitcast

What would it look like without this extension? If we modeled it as if all the register values were already on the stack (an extension of the current way where the singular value is modeled as being already on the stack, if I understand it correctly?)? If it's decided that the best approach is to introduce something like DW_OP_LLVM_register - might be worth migrating to that first (basically

Currently there is a series of patches undergoing review[0] that seek to enable the use of multiple IR/MIR values when describing a source variable's location. The current plan for the MIR is to add a new instruction, DBG_VALUE_LIST, that supports this functionality by having a variable number of operands. It may be better however to simply replace the existing DBG_VALUE behaviour entirely

> On Nov 18, 2019, at 8:33 AM, Jeremy Morse <jeremy.morse.llvm at gmail.com> wrote: > > Hi llvm-dev@, > > Switching focus to the LLVM implementation, the significant change is > using dbg.value's first operand to refer to a DILocalVariable, rather > than a Value. There's some impedance mismatch here, because all the > documentation (for example in the

*From:* flang-dev <flang-dev-bounces at lists.flang-compiler.org> *On Behalf Of *Eric Schweitz (PGI) *Sent:* Thursday, November 01, 2018 1:02 PM *To:* flang-dev at lists.flang-compiler.org *Subject:* [Flang-dev] RFC: Adding debug information to LLVM to support Fortran In order to support debugging in the Flang project, work has been done to extend LLVM debug information for the Fortran

On Wed, Sep 6, 2017 at 10:01 AM, David Blaikie <dblaikie at gmail.com> wrote: > On Tue, Sep 5, 2017 at 1:00 PM Reid Kleckner via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> LLVM SSA values obviously do not have an address that we can take and >> they don’t live in registers, so neither the default memory location model >> nor DW_OP_regN make sense

Hi all, Consider the following example: define void @fn(i8* %buf) #0 { entry: %arrayidx = getelementptr i8* %buf, i64 18 tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %arrayidx, i8* %buf, i64 18, i32 1, i1 false) %arrayidx1 = getelementptr i8* %buf, i64 18 store i8 1, i8* %arrayidx1, align 1 tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %buf, i8* %arrayidx, i64 18, i32 1, i1 false)

Currently, the debug intrinsic functions each have 3 arguments: an SSA value representing either the address or Value of a local variable, a DILocalVariable, and a complex expression. If the SSA value is an Instruction, and that Instruction is at some point deleted, we attempt to salvage the SSA value by recreating the instruction within the complex expression. If the instruction cannot be

On Wed, Sep 6, 2017 at 5:01 PM, David Blaikie <dblaikie at gmail.com> wrote: > On Wed, Sep 6, 2017 at 2:01 PM Reid Kleckner <rnk at google.com> wrote: > >> On Wed, Sep 6, 2017 at 10:01 AM, David Blaikie <dblaikie at gmail.com> >> wrote: >> >>> I guess you described this already, but talking it through for >>> myself/maybe others will

Hi All, I came across a FileCheck failure I don't understand why. The example code below: void test1() { ... code ... // CHECK-LABEL: @test1 // CHECK: void @llvm.memcpy.p0i8.p0i8.i32 - (1) } void dummy() { // make (1) match ... code ... // CHECK-LABEL: @dummy } void test2() { ... code ... // CHECK-LABEL: @test2 //

The front end I'm building for an existing interpreted language is unfortunately producing output similar to this far too often; define void @foo(i8* nocapture %dest, i8* nocapture %src, i32 %len) nounwind { %1 = tail call noalias i8* @malloc(i32 %len) nounwind tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* %1, i8* %src, i32 %len, i32 1, i1 false) tail call void

> I can see how that could potentially be useful. I'm not sure how often we could practically make use of a situation like this, but I understand your motivation. Indeed, I don't expect us to cancel out DWARF expressions like that very often. Although that edge case is likely to be very rare, the _direct operator itself will appear very frequently, as it would be used for every

On Tue, Jan 5, 2016 at 6:59 PM, Adrian Prantl <aprantl at apple.com> wrote: > Thanks for the clarification, Paul! > Keno, just a few more questions for my understanding: > > > - Indicating that a value changed at source level (e.g. because an > > assignment occurred) > > This is done by a key call. Correct > > - Indicating that the same

>As the person who has advocated for DW_OP_LLVM_arg(N) before, my main motivation was to resolve the ambiguity of constant DIExpressions: As a worst-case example: > >dbg.value(%undef, !DILocalVariable(x), DIExpression(DW_OP_constu, 42)) > >Is this undefined, or constant 42? > >But if we make dbg.value fully variadic with all parameters pushed to the stack ahead of time, we can