similar to: MachineVerifier and undef

Displaying 20 results from an estimated 8000 matches similar to: "MachineVerifier and undef"

2018 Jan 23
0
MachineVerifier and undef
Thanks Krzysztof. That's very helpful - I was missing the distinction between a register containing an undefined value and a register marked as containing an undefined value. Cheers! On 1/23/18, via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Send llvm-dev mailing list submissions to > llvm-dev at lists.llvm.org > > To subscribe or unsubscribe via the World Wide Web,
2017 Jul 27
2
Tail merging "undef" with a defined register: wrong code
Yes, immediately after branch folding the code would still behave the same as the original. At the same time, any subsequent optimization may "exploit" the incorrect liveness information to do something bad. If you add -run-pass if-converter, you'll get: # After If Converter # Machine code for function fred: IsSSA, NoPHIs, TracksLiveness, NoVRegs BB#0: %R0<def>
2019 Sep 02
2
virtual subregister liveness?
On Fri, 2019-08-30 at 10:03 -0700, Quentin Colombet wrote: > > On Aug 30, 2019, at 8:31 AM, Jesper Antonsson via llvm-dev < > > llvm-dev at lists.llvm.org> wrote: > > > > Hi, > > > > After dead-mi-elimination I'm experiencing a machine verifier > > failure > > at this virtual subregister write: > > > > %5.sub1 = COPY undef
2017 Jul 28
2
Tail merging "undef" with a defined register: wrong code
I've looked into that and it's not going to be simple, unfortunately. Here's the original example again: --- name: fred tracksRegLiveness: true body: | bb.0: successors: %bb.1, %bb.2 J2_jumpt undef %p0, %bb.2, implicit-def %pc J2_jump %bb.1, implicit-def %pc bb.1: successors: %bb.3 %r0 = L2_loadruh_io undef %r0, 0 PS_storerhabs 0, killed
2019 Aug 30
2
virtual subregister liveness?
Hi, After dead-mi-elimination I'm experiencing a machine verifier failure at this virtual subregister write: %5.sub1 = COPY undef %11 The machine verifier essentially complains that the rest of the register is undefined (a subregister write implies a "read" of the other parts). So the problem is that dead-mi-elimination has removed the previously existing defines of %5.sub0.
2020 Nov 19
1
Problems with undef subranges in identity copies
Hi, I'm stuck trying to fix a variety of problems that occur with undef subregisters when the register coalescer eliminates identity copies. The fundamental problem is complexity from the fact that undef values are a special case since they don't have an associated VNInfo/Segment unless the value is used across blocks. For example, in this case, %0 has 2 subregisters sub0 and sub1:
2017 Jul 27
2
Tail merging "undef" with a defined register: wrong code
The comment in test/CodeGen/X86/branchfolding-undef.mir states that such merging is legal, however doing so can actually generate wrong code: Consider this (valid code): --- name: fred tracksRegLiveness: true body: | bb.0: successors: %bb.1, %bb.2 J2_jumpt undef %p0, %bb.2, implicit-def %pc J2_jump %bb.1, implicit-def %pc bb.1: successors: %bb.3 %r0 =
2020 Apr 09
2
Supporting freeze in GlobalISel / freeze semantics in MIR
Hi all, After a recent upstream merge into our downstream sources we are suddenly encountering the freeze instruction in LLVM IR for div/rem pairs. This seems to be related to [1]. Our downstream target is GlobalISel only and unfortunately GlobalISel doesn't support this instruction yet, so most of our internal test-suite is now breaking due to GlobalISel not being able to translate this
2019 Apr 11
2
Upper case vs lower case in printed and parsed MIR
I am confused about the rules for when upper and lower case letters should be used in MIR. As an example our downstream target has upper case letters in its sub-register indices and as a result we cannot import exported MIR without manually 'lower casing' it first which is obviously rather annoying. Looking in https://llvm.org/docs/MIRLangRef.html it is stated that instruction names are
2014 Nov 06
2
[LLVMdev] Should the MachineVerifier accept a MBB with a single (landing pad) successor?
Hi all, I've been investigating a machine verifier failure on the attached testcase, and I'm tempted to say the verifier is wrong and should accept it. Skip the description for the proposed change. On AArch64, the verifier complains with: *** Bad machine code: MBB exits via unconditional branch but doesn't have exactly one CFG successor! *** - function: t4 - basic
2012 Oct 29
1
[LLVMdev] Data flow/liveness in register pairs
Hello, Consider this code (this is all after register allocation): R0<def> = ... R0 // Set lower half (based on the previous value) R1<def> = ... // Set upper half ... = R0_R1 // Use the pair It is my understanding that the use of the whole pair will need to have some sort of a reaching def, i.e. the code will need at least those flags: R0<def> =
2017 Nov 13
2
Reaching definitions on Machine IR post register allocation
Hi Venu, This is happening because there is an implicit def of ECX on the COPY instruction. This was an issue on Hexagon as well. Let me give you some background. There are two kinds of implicit defs (and implicit uses, but I'll refer only to defs for brevity): (1) Those that indicate that some physical register (that is not an operand) is modified by a given instruction (EFLAGS is a good
2017 Nov 24
2
Reaching definitions on Machine IR post register allocation
Hi Krzysztof, In one of your earlier emails in this thread you mentioned that you had some changes which add extra aliases for subregisters. Did you mean for X86? And is it extra register units that you added or aliases? I tried adding extra register units for X86 through some changes in CodeGenRegisters.cpp in TableGen but I am seeing a runtime error in one of my test cases possibly due to the
2008 Oct 13
2
[LLVMdev] INSERT_SUBREG node.
On Thu, 2008-10-02 at 11:19 -0700, Evan Cheng wrote: > > On Oct 2, 2008, at 11:02 AM, Sanjiv.Gupta at microchip.com wrote: > > > What’s the value produced by an INSERT_SUBREG node? Is it a chain? > > > No, insert_subreg returns a value: > > > v1 = insert_subreg v2, v3, idx > > > v1 and v2 will have the same type, e.g. i16, and v3 must have a >
2017 Nov 01
2
Reaching definitions on Machine IR post register allocation
Hi Geoff/Krzyssztof, Wouldn't the isRenamable() change be required even for the RDF based copy propagation? Maybe Hexagon does not impose ABI/ISA restrictions which require specific registers to be used in specific contexts. Also, if Geoff's copy propagation pass is invoked post-RA wouldn't it need to handle the x86 ISA feature which allows 8 bit/16 bit values to be moved into a
2008 Oct 15
2
[LLVMdev] INSERT_SUBREG node.
On Tue, 2008-10-14 at 10:19 -0700, Evan Cheng wrote: > You need to specify sub-register == super-register, idx relationship. > See X86RegisterInfo.td: > > def x86_subreg_8bit : PatLeaf<(i32 1)>; > def x86_subreg_16bit : PatLeaf<(i32 2)>; > def x86_subreg_32bit : PatLeaf<(i32 3)>; > > def : SubRegSet<1, [AX, CX, DX, BX, SP, BP, SI, DI, >
2018 Feb 13
2
Undef physical registers?
Hi, I'm a bit unsure of the semantics of undef physical registers. The explanations I've seen in the code and in the langref seems to pertain more to constant values and virtual registers. What I really want to achieve is a push-pop of a register to have a temporary to work with, without having to check if this register is defined or not. However, whenever the reg is not defined before
2018 Mar 20
2
MIR YAML deserialisation failure
Valentin, in terms of limitations as Sean pointed out, an important one is that .mir doesn't have MachineFunctionInfo which may result in failure on accesses to global variables due to use of register X2. The verifier considers it an undefined register. Also, it's probably easier to reduce test cases using bugpoint starting from an IR test case. With the code you provided, I get a
2008 Oct 14
0
[LLVMdev] INSERT_SUBREG node.
You need to specify sub-register == super-register, idx relationship. See X86RegisterInfo.td: def x86_subreg_8bit : PatLeaf<(i32 1)>; def x86_subreg_16bit : PatLeaf<(i32 2)>; def x86_subreg_32bit : PatLeaf<(i32 3)>; def : SubRegSet<1, [AX, CX, DX, BX, SP, BP, SI, DI, R8W, R9W, R10W, R11W, R12W, R13W, R14W, R15W], [AL, CL,
2018 Nov 12
3
[RFC] Tablegen-erated GlobalISel Combine Rules
> On Nov 10, 2018, at 03:28, Nicolai Hähnle <nhaehnle at gmail.com> wrote: > > Thank you for the detailed reply! There's a lot to digest :) Let me try to address most of it. > > > [snip] >>> I also think you should have 'ins' and 'outs' separately; after all, a predicate may have to do a combined check on two matched registers / operands,