[llvm] r268539 - [AArch64] Use the reciprocal estimation machinery
Eric Christopher via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 20 08:32:11 PDT 2016
On Tue, Sep 20, 2016 at 5:15 AM Evandro Menezes <e.menezes at samsung.com>
wrote:
> Hi, Eric.
>
> All the other targets which use the Newton series approximations include
> a Subtarget in TargetMatchine. This change merely follows the pattern
> already found in the PowerPC and X86 ports.
>
>
This patch is definitely beyond the level of post-commit review for areas
you've typically touched and I'm asking you to revert it. In addition, I'll
ask Hal to revert the patch in r241985 while we come up with a better
implementation.
> Thus, if anything, the discussion should be broader than AArch64. Until
> that's settled, it's preferable to keep this patch until an universal
> solution is found, IMO.
>
>
This discussion has already happened when I did the work in the first place
to deal with function based subtargets and LTO. In addition, the work that
you've done has had a flaw explicitly pointed out - you'll have different
values that won't get reset between functions.
All subtarget dependent machinery is (unless the target really doesn't care
like most of the gpus) based on the function and you can't depend upon a
single subtarget for any TargetMachine. This means that, in general, you
also can't depend upon it for initializing the pass structure or overall
backend machinery.
As I mentioned before, during LTO if you compile two functions with
different cpu options and link them together you should get different code
and tuning, in this case you've now broken it for the reciprocal code.
-eric
> Thank you,
>
> --
> Evandro Menezes
>
> On 09/19/16 19:49, Eric Christopher wrote:
> > Hi Evandro,
> >
> > I'm going to ask you to revert this patch please. There are a few
> reasons:
> >
> > a) I don't see a review thread here? This changes the port quite a bit.
> >
> >
> > ///
> > AArch64TargetMachine::AArch64TargetMachine(const Target &T, const
> > Triple &TT,
> > @@ -149,7 +173,8 @@ AArch64TargetMachine::AArch64TargetMachi
> > : LLVMTargetMachine(T, computeDataLayout(TT, LittleEndian),
> > TT, CPU, FS,
> > Options, RM, CM, OL),
> > TLOF(createTLOF(getTargetTriple())),
> > - isLittle(LittleEndian) {
> > + Subtarget(TT, CPU, FS, *this, LittleEndian) {
> > + initReciprocals(*this, Subtarget);
> > initAsmInfo();
> > }
> >
> > @@ -189,7 +214,7 @@ AArch64TargetMachine::getSubtargetImpl(c
> > // function that reside in TargetOptions.
> > resetTargetOptions(F);
> > I = llvm::make_unique<AArch64Subtarget>(TargetTriple, CPU,
> > FS, *this,
> > - isLittle);
> > + Subtarget.isLittleEndian());
> > #ifndef LLVM_BUILD_GLOBAL_ISEL
> > GISelAccessor *GISel = new GISelAccessor();
> > #else
> >
> > Modified: llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.h
> > URL:
> >
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.h?rev=268539&r1=268538&r2=268539&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.h (original)
> > +++ llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.h Wed May
> > 4 15:18:27 2016
> > @@ -46,7 +46,7 @@ public:
> > }
> >
> > private:
> > - bool isLittle;
> > + AArch64Subtarget Subtarget;
> > };
> >
> >
> > These changes aren't correct. There is no need and it's currently
> > invalid for the AArch64 port to depend on a single global subtarget
> > for all configuration. This is going to break anything that depends on
> > changing subtargets on a function by function basis (including
> > different -mcpu flags in different translation units or different
> > options).
> >
> > You're going to need to do all of these changes in a different way and
> > I haven't had time to look to see what's going on.
> >
> > Thanks!
> >
> > -eric
> >
> >
> > // AArch64leTargetMachine - AArch64 little endian target machine.
> >
> > Added: llvm/trunk/test/CodeGen/AArch64/recp-fastmath.ll
> > URL:
> >
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/recp-fastmath.ll?rev=268539&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/AArch64/recp-fastmath.ll (added)
> > +++ llvm/trunk/test/CodeGen/AArch64/recp-fastmath.ll Wed May 4
> > 15:18:27 2016
> > @@ -0,0 +1,79 @@
> > +; RUN: llc < %s -mtriple=aarch64 -mattr=neon -recip=!div,!vec-div
> > | FileCheck %s --check-prefix=FAULT
> > +; RUN: llc < %s -mtriple=aarch64 -mattr=neon -recip=div,vec-div
> > | FileCheck %s
> > +
> > +define float @frecp(float %x) #0 {
> > + %div = fdiv fast float 1.0, %x
> > + ret float %div
> > +
> > +; FAULT-LABEL: frecp:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fmov
> > +; FAULT-NEXT: fdiv
> > +
> > +; CHECK-LABEL: frecp:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: frecpe
> > +; CHECK-NEXT: fmov
> > +}
> > +
> > +define <2 x float> @f2recp(<2 x float> %x) #0 {
> > + %div = fdiv fast <2 x float> <float 1.0, float 1.0>, %x
> > + ret <2 x float> %div
> > +
> > +; FAULT-LABEL: f2recp:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fmov
> > +; FAULT-NEXT: fdiv
> > +
> > +; CHECK-LABEL: f2recp:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frecpe
> > +}
> > +
> > +define <4 x float> @f4recp(<4 x float> %x) #0 {
> > + %div = fdiv fast <4 x float> <float 1.0, float 1.0, float 1.0,
> > float 1.0>, %x
> > + ret <4 x float> %div
> > +
> > +; FAULT-LABEL: f4recp:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fmov
> > +; FAULT-NEXT: fdiv
> > +
> > +; CHECK-LABEL: f4recp:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frecpe
> > +}
> > +
> > +define double @drecp(double %x) #0 {
> > + %div = fdiv fast double 1.0, %x
> > + ret double %div
> > +
> > +; FAULT-LABEL: drecp:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fmov
> > +; FAULT-NEXT: fdiv
> > +
> > +; CHECK-LABEL: drecp:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: frecpe
> > +; CHECK-NEXT: fmov
> > +}
> > +
> > +define <2 x double> @d2recp(<2 x double> %x) #0 {
> > + %div = fdiv fast <2 x double> <double 1.0, double 1.0>, %x
> > + ret <2 x double> %div
> > +
> > +; FAULT-LABEL: d2recp:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fmov
> > +; FAULT-NEXT: fdiv
> > +
> > +; CHECK-LABEL: d2recp:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frecpe
> > +}
> > +
> > +attributes #0 = { nounwind "unsafe-fp-math"="true" }
> >
> > Added: llvm/trunk/test/CodeGen/AArch64/sqrt-fastmath.ll
> > URL:
> >
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/sqrt-fastmath.ll?rev=268539&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/AArch64/sqrt-fastmath.ll (added)
> > +++ llvm/trunk/test/CodeGen/AArch64/sqrt-fastmath.ll Wed May 4
> > 15:18:27 2016
> > @@ -0,0 +1,158 @@
> > +; RUN: llc < %s -mtriple=aarch64 -mattr=neon
> > -recip=!sqrt,!vec-sqrt | FileCheck %s --check-prefix=FAULT
> > +; RUN: llc < %s -mtriple=aarch64 -mattr=neon
> > -recip=sqrt,vec-sqrt | FileCheck %s
> > +
> > +declare float @llvm.sqrt.f32(float) #1
> > +declare double @llvm.sqrt.f64(double) #1
> > +declare <2 x float> @llvm.sqrt.v2f32(<2 x float>) #1
> > +declare <4 x float> @llvm.sqrt.v4f32(<4 x float>) #1
> > +declare <2 x double> @llvm.sqrt.v2f64(<2 x double>) #1
> > +
> > +define float @fsqrt(float %a) #0 {
> > + %1 = tail call fast float @llvm.sqrt.f32(float %a)
> > + ret float %1
> > +
> > +; FAULT-LABEL: fsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: fsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <2 x float> @f2sqrt(<2 x float> %a) #0 {
> > + %1 = tail call fast <2 x float> @llvm.sqrt.v2f32(<2 x float> %a)
> #2
> > + ret <2 x float> %1
> > +
> > +; FAULT-LABEL: f2sqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: f2sqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: mov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <4 x float> @f4sqrt(<4 x float> %a) #0 {
> > + %1 = tail call fast <4 x float> @llvm.sqrt.v4f32(<4 x float> %a)
> #2
> > + ret <4 x float> %1
> > +
> > +; FAULT-LABEL: f4sqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: f4sqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: mov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define double @dsqrt(double %a) #0 {
> > + %1 = tail call fast double @llvm.sqrt.f64(double %a)
> > + ret double %1
> > +
> > +; FAULT-LABEL: dsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: dsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <2 x double> @d2sqrt(<2 x double> %a) #0 {
> > + %1 = tail call fast <2 x double> @llvm.sqrt.v2f64(<2 x double>
> > %a) #2
> > + ret <2 x double> %1
> > +
> > +; FAULT-LABEL: d2sqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: d2sqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: mov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define float @frsqrt(float %a) #0 {
> > + %1 = tail call fast float @llvm.sqrt.f32(float %a)
> > + %2 = fdiv fast float 1.000000e+00, %1
> > + ret float %2
> > +
> > +; FAULT-LABEL: frsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: frsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <2 x float> @f2rsqrt(<2 x float> %a) #0 {
> > + %1 = tail call fast <2 x float> @llvm.sqrt.v2f32(<2 x float> %a)
> #2
> > + %2 = fdiv fast <2 x float> <float 1.000000e+00, float
> > 1.000000e+00>, %1
> > + ret <2 x float> %2
> > +
> > +; FAULT-LABEL: f2rsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: f2rsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <4 x float> @f4rsqrt(<4 x float> %a) #0 {
> > + %1 = tail call fast <4 x float> @llvm.sqrt.v4f32(<4 x float> %a)
> #2
> > + %2 = fdiv fast <4 x float> <float 1.000000e+00, float
> > 1.000000e+00, float 1.000000e+00, float 1.000000e+00>, %1
> > + ret <4 x float> %2
> > +
> > +; FAULT-LABEL: f4rsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: f4rsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define double @drsqrt(double %a) #0 {
> > + %1 = tail call fast double @llvm.sqrt.f64(double %a)
> > + %2 = fdiv fast double 1.000000e+00, %1
> > + ret double %2
> > +
> > +; FAULT-LABEL: drsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: drsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +define <2 x double> @d2rsqrt(<2 x double> %a) #0 {
> > + %1 = tail call fast <2 x double> @llvm.sqrt.v2f64(<2 x double>
> > %a) #2
> > + %2 = fdiv fast <2 x double> <double 1.000000e+00, double
> > 1.000000e+00>, %1
> > + ret <2 x double> %2
> > +
> > +; FAULT-LABEL: d2rsqrt:
> > +; FAULT-NEXT: BB#0
> > +; FAULT-NEXT: fsqrt
> > +
> > +; CHECK-LABEL: d2rsqrt:
> > +; CHECK-NEXT: BB#0
> > +; CHECK-NEXT: fmov
> > +; CHECK-NEXT: frsqrte
> > +}
> > +
> > +attributes #0 = { nounwind "unsafe-fp-math"="true" }
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>
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> >
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>
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