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

Wed Nov 8 23:31:24 PST 2017

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<mailto: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<mailto: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-mirror/llvm.git 761e543ac73ddc55d2cf3c6892fe18eecb0c89d9)"}

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