[llvm] r216914 - Revert: [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.

Tue Sep 16 05:11:25 PDT 2014

----- Original Message -----
> From: "Andrea Di Biagio" <andrea.dibiagio at gmail.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "Andrea Di Biagio" <Andrea_DiBiagio at sn.scee.net>, "llvm-commits at cs.uiuc.edu for LLVM" <llvm-commits at cs.uiuc.edu>
> Sent: Tuesday, September 16, 2014 4:30:42 AM
> Subject: Re: [llvm] r216914 - Revert: [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.
> 
> On Tue, Sep 16, 2014 at 5:50 AM, Hal Finkel <hfinkel at anl.gov> wrote:
> > ----- Original Message -----
> >> From: "Andrea Di Biagio" <Andrea_DiBiagio at sn.scee.net>
> >> To: llvm-commits at cs.uiuc.edu
> >> Sent: Tuesday, September 2, 2014 12:22:50 PM
> >> Subject: [llvm] r216914 - Revert: [APFloat] Fixed a bug in method
> >>     'fusedMultiplyAdd'.
> >>
> >> Author: adibiagio
> >> Date: Tue Sep  2 12:22:49 2014
> >> New Revision: 216914
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=216914&view=rev
> >> Log:
> >> Revert: [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.
> >>
> >> This reverts revision 216913; the new test added at revision
> >> 216913
> >> caused regression failures on a couple of buildbots.
> >
> > Did we ever figure this out?
> >
> >  -Hal
> 
> Unfortunately not..
> Basically, only for five buildbots the fused-multiply-add from test
> case @PR20832 (added by test fold-builtin-fma.ll) was folded to a
> completely bogus number. Interestingly, each failing buildbot found a
> different number for the failing test case. That really confused me:
> in case of an error, I was expecting _all_ the buildbots to fail with
> the same error; instead, only a few builbots failed each time with
> different results (I see if I can find the blame emails.. Hopefully I
> didn't delete them).
> 
> Anyway, I tried to reproduce the regression failure on a different
> x86
> machine (as far as I remember, three of the failing builbots were
> bootstrapping clang on a x86_64 with both host and target
> x86_64-unknown-linux-gnu). I tried on two other x86 machines with the
> same configuration. Unfortunately I was never able to reproduce the
> failure (it always worked for me).

Strange. Which bots failed?

 -Hal

> 
> >
> >>
> >>
> >> Removed:
> >>     llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> >> Modified:
> >>     llvm/trunk/lib/Support/APFloat.cpp
> >>
> >> Modified: llvm/trunk/lib/Support/APFloat.cpp
> >> URL:
> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APFloat.cpp?rev=216914&r1=216913&r2=216914&view=diff
> >> ==============================================================================
> >> --- llvm/trunk/lib/Support/APFloat.cpp (original)
> >> +++ llvm/trunk/lib/Support/APFloat.cpp Tue Sep  2 12:22:49 2014
> >> @@ -1801,7 +1801,7 @@ APFloat::fusedMultiplyAdd(const APFloat
> >>       extended-precision calculation.  */
> >>    if (isFiniteNonZero() &&
> >>        multiplicand.isFiniteNonZero() &&
> >> -      addend.isFinite()) {
> >> +      addend.isFiniteNonZero()) {
> >>      lostFraction lost_fraction;
> >>
> >>      lost_fraction = multiplySignificand(multiplicand, &addend);
> >>
> >> Removed:
> >> llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> >> URL:
> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll?rev=216913&view=auto
> >> ==============================================================================
> >> --- llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> >> (original)
> >> +++ llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> >> (removed)
> >> @@ -1,119 +0,0 @@
> >> -; RUN: opt -instsimplify -S < %s | FileCheck %s
> >> -
> >> -; Fixes PR20832
> >> -; Make sure that we correctly fold a fused multiply-add where
> >> operands
> >> -; are all finite constants and addend is zero.
> >> -
> >> -declare double @llvm.fma.f64(double, double, double)
> >> -
> >> -
> >> -define double @PR20832()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @PR20832(
> >> -; CHECK: ret double 5.600000e+01
> >> -
> >> -; Test builtin fma with all finite non-zero constants.
> >> -define double @test_all_finite()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 5.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_all_finite(
> >> -; CHECK: ret double 6.100000e+01
> >> -
> >> -; Test builtin fma with a +/-NaN addend.
> >> -define double @test_NaN_addend()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 0x7FF8000000000000)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_addend(
> >> -; CHECK: ret double 0x7FF8000000000000
> >> -
> >> -define double @test_NaN_addend_2()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 0xFFF8000000000000)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_addend_2(
> >> -; CHECK: ret double 0xFFF8000000000000
> >> -
> >> -; Test builtin fma with a +/-Inf addend.
> >> -define double @test_Inf_addend()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 0x7FF0000000000000)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_addend(
> >> -; CHECK: ret double 0x7FF0000000000000
> >> -
> >> -define double @test_Inf_addend_2()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double
> >> 0xFFF0000000000000)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_addend_2(
> >> -; CHECK: ret double 0xFFF0000000000000
> >> -
> >> -; Test builtin fma with one of the operands to the multiply being
> >> +/-NaN.
> >> -define double @test_NaN_1()  {
> >> -  %1 = call double @llvm.fma.f64(double 0x7FF8000000000000,
> >> double
> >> 8.0, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_1(
> >> -; CHECK: ret double 0x7FF8000000000000
> >> -
> >> -
> >> -define double @test_NaN_2()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double
> >> 0x7FF8000000000000, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_2(
> >> -; CHECK: ret double 0x7FF8000000000000
> >> -
> >> -
> >> -define double @test_NaN_3()  {
> >> -  %1 = call double @llvm.fma.f64(double 0xFFF8000000000000,
> >> double
> >> 8.0, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_3(
> >> -; CHECK: ret double 0x7FF8000000000000
> >> -
> >> -
> >> -define double @test_NaN_4()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double
> >> 0xFFF8000000000000, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_NaN_4(
> >> -; CHECK: ret double 0x7FF8000000000000
> >> -
> >> -
> >> -; Test builtin fma with one of the operands to the multiply being
> >> +/-Inf.
> >> -define double @test_Inf_1()  {
> >> -  %1 = call double @llvm.fma.f64(double 0x7FF0000000000000,
> >> double
> >> 8.0, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_1(
> >> -; CHECK: ret double 0x7FF0000000000000
> >> -
> >> -
> >> -define double @test_Inf_2()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double
> >> 0x7FF0000000000000, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_2(
> >> -; CHECK: ret double 0x7FF0000000000000
> >> -
> >> -
> >> -define double @test_Inf_3()  {
> >> -  %1 = call double @llvm.fma.f64(double 0xFFF0000000000000,
> >> double
> >> 8.0, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_3(
> >> -; CHECK: ret double 0xFFF0000000000000
> >> -
> >> -
> >> -define double @test_Inf_4()  {
> >> -  %1 = call double @llvm.fma.f64(double 7.0, double
> >> 0xFFF0000000000000, double 0.0)
> >> -  ret double %1
> >> -}
> >> -; CHECK-LABEL: @test_Inf_4(
> >> -; CHECK: ret double 0xFFF0000000000000
> >> -
> >>
> >>
> >> _______________________________________________
> >> llvm-commits mailing list
> >> llvm-commits at cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >>
> >
> > --
> > Hal Finkel
> > Assistant Computational Scientist
> > Leadership Computing Facility
> > Argonne National Laboratory
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory