[llvm-dev] [GlobalISel] [X86] unable to legalize instruction

Fri Nov 10 12:00:26 PST 2017

Thank you very much for your reply. That helped.

I spent a little bit of time debugging the failure. It appears that
X86LegalizerInfo does not (yet?) set up the required actions and tables for
the opcode G_SDIV. I have not looked at GlobalISel phase earlier, but am
curious to learn of the reasons for G_SDIV not being supported, yet. Are
there any pointers that give some background? Of course, I hope to continue
to dig irrespectively (albeit slowly :-)).

Thanks again!

Bharadwaj

On Nov 8, 2017 11:31 PM, "Breger, Igor" <igor.breger at intel.com> wrote:

Hi ,

Currently GobalIsel like FastIsel  designed to use fallback to DAGIsel in
case of failure.

You can use -global-isel-abort=2 option.

   llc -global-isel -pass-remarks-missed="gisel-*" *-global-isel-abort=2  *
simple_foo.ll

Regards,

Igor

*From:* S. Bharadwaj Yadavalli [mailto:bharadwajy at gmail.com]
*Sent:* Thursday, November 09, 2017 03:36
*To:* Aditya Nandakumar <proaditya at gmail.com>
*Cc:* Craig Topper <craig.topper at gmail.com>; llvm-dev <
llvm-dev at lists.llvm.org>; Breger, Igor <igor.breger at intel.com>
*Subject:* Re: [llvm-dev] [GlobalISel] [X86] unable to legalize instruction

Sorry for the late follow-up.

Here is the output with the suggested option:

$ llc -global-isel -pass-remarks-missed="gisel-*" simple_foo.ll

LLVM ERROR: unable to legalize instruction: %vreg17<def>(s32) = G_SDIV
%vreg15, %vreg16; (in function: foo)

Thanks for any help/suggestions.

On Wed, Oct 11, 2017 at 8:13 PM, Aditya Nandakumar <proaditya at gmail.com>
wrote:

I believe if you pass(iirc) -pass-remarks-missed=“gisel-*”, it’ll print the
instruction it failed to legalize.

Sent from my iPhone

On Oct 11, 2017, at 6:44 PM, S. Bharadwaj Yadavalli via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

Thanks for your quick reply.

Here its is:

===========

; ModuleID = 'simple_foo.c'

source_filename = "simple_foo.c"

target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"

target triple = "x86_64-apple-macosx10.13.0"

; Function Attrs: noinline nounwind optnone ssp uwtable

define i32 @foo(i32 %a, i32 %b, i32 %c) #0 {

entry:

  %retval = alloca i32, align 4

  %a.addr = alloca i32, align 4

  %b.addr = alloca i32, align 4

  %c.addr = alloca i32, align 4

  %sum = alloca i32, align 4

  %sum1 = alloca i32, align 4

  store i32 %a, i32* %a.addr, align 4

  store i32 %b, i32* %b.addr, align 4

  store i32 %c, i32* %c.addr, align 4

  %0 = load i32, i32* %c.addr, align 4

  %cmp = icmp ne i32 %0, 0

  br i1 %cmp, label %if.then, label %if.else

if.then:                                          ; preds = %entry

  %1 = load i32, i32* %a.addr, align 4

  %2 = load i32, i32* %b.addr, align 4

  %add = add nsw i32 %1, %2

  store i32 %add, i32* %sum, align 4

  %3 = load i32, i32* %sum, align 4

  %4 = load i32, i32* %c.addr, align 4

  %div = sdiv i32 %3, %4

  store i32 %div, i32* %retval, align 4

  br label %return

if.else:                                          ; preds = %entry

  %5 = load i32, i32* %a.addr, align 4

  %6 = load i32, i32* %b.addr, align 4

  %add2 = add nsw i32 %5, %6

  store i32 %add2, i32* %sum1, align 4

  %7 = load i32, i32* %sum1, align 4

  store i32 %7, i32* %retval, align 4

  br label %return

return:                                           ; preds = %if.else,
%if.then

  %8 = load i32, i32* %retval, align 4

  ret i32 %8

}

attributes #0 = { noinline nounwind optnone ssp uwtable
"correctly-rounded-divide-sqrt-fp-math"="false"
"disable-tail-calls"="false" "less-precise-fpmad"="false"
"no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false" "no-jump-tables"="false"
"no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false"
"no-trapping-math"="false" "stack-protector-buffer-size"="8"
"target-cpu"="penryn" "target-features"="+cx16,+fxsr
,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false"
"use-soft-float"="false" }

!llvm.module.flags = !{!0, !1}

!llvm.ident = !{!2}

!0 = !{i32 1, !"wchar_size", i32 4}

!1 = !{i32 7, !"PIC Level", i32 2}

!2 = !{!"clang version 6.0.0 (https://github.com/llvm-mirror/clang.git
9563977e8bce81b1dd88ce7579e36a055e3ff90b) (https://github.com/llvm-mirro
r/llvm.git 761e543ac73ddc55d2cf3c6892fe18eecb0c89d9)"}

On Wed, Oct 11, 2017 at 5:50 PM, Craig Topper <craig.topper at gmail.com>
wrote:

global-isel for x86 is still very much a work in progress. What was the
content for simple_foo.ll?

~Craig

On Wed, Oct 11, 2017 at 5:39 PM, S. Bharadwaj Yadavalli via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

Hi,

Can someone please let me know if I can expect GlobalISel to be functional
for x86/x86-64 targets?

$ uname -a

Darwin <Machine-Name> 17.0.0 Darwin Kernel Version 17.0.0: Thu Aug 24
21:48:19 PDT 2017; root:xnu-4570.1.46~2/RELEASE_X86_64 x86_64

Following is the command I used that resulted in an error :

~/github/build/llvm/Debug/bin/llc -global-isel -O0 simple_foo.ll

LLVM ERROR: unable to legalize instruction (in function: foo)

llc without the -global-isel option works fine.

I built clang/llc using the sources with the following tips:

LLVM

761e543ac73 (HEAD -> master, origin/master, origin/HEAD) [Transforms] Fix
some Clang-tidy modernize and Include What You Use warnings; other minor
fixes (NFC).

clang

9563977e8b (HEAD -> master, origin/master, origin/HEAD) [X86] Add support
for 'amdfam17h' to __builtin_cpu_is to match gcc.

Thanks,

Bharadwaj

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