[gcc(refs/users/meissner/heads/work067)] Fix SFmode subreg of DImode and TImode

[Michael Meissner]

https://gcc.gnu.org/g:5cdcc6b5c2ebcec93e153fc80e5ff6804eed05d4

commit 5cdcc6b5c2ebcec93e153fc80e5ff6804eed05d4
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Wed Sep 8 17:51:36 2021 -0400

    Fix SFmode subreg of DImode and TImode
    
    I first noticed it in building the Spec 2017 wrf_r and blender_r
    benchmarks.  Once I applied this patch, I also noticed several of the
    tests now pass.
    
    This patch fixes the breakage in the PowerPC due to a recent change in SUBREG
    behavior.  While it is arguable that the patch that caused the breakage should
    be reverted, this patch should be a bandage to prevent these changes from
    happening again.
    
    The core of the problem is we need to treat SUBREG's of SFmode and SImode
    specially on the PowerPC.  This is due to the fact that SFmode values that are
    in the vector and floating point registers are represented as DFmode.  When we
    want to do a direct move between the GPR registers and the vector registers, we
    have to convert the value from the DFmode representation to/from the SFmode
    representation.
    
    By doing this special processing instead of doing the transfer via store and
    load, we were able to speed up the math library which at times want to use the
    SFmode values in a union, and do logical operations on it (to test exponent
    ranges, etc.) and then move it over to use as a floating point value.
    
    I did a bootstrap build on a little endian power9 system with and without the
    patch applied.  There was no regression in the tests.  I'm doing a build on a
    big endian power8 system, but it hasn't finished yet as I sent this email.  I
    will check on the big endian progress tomorrow morning.
    
    The following tests now pass once again with the test.
    
            C tests:
            ========
            gcc.c-torture/compile/20071102-1.c
            gcc.c-torture/compile/pr55921.c
            gcc.c-torture/compile/pr85945.c
            gcc.c-torture/execute/complex-3.c
            gcc.dg/atomic/c11-atomic-exec-1.c
            gcc.dg/atomic/c11-atomic-exec-2.c
            gcc.dg/atomic/c11-atomic-exec-4.c
            gcc.dg/atomic/c11-atomic-exec-5.c
            gcc.dg/c11-atomic-2.c
            gcc.dg/pr42475.c
            gcc.dg/pr47201.c
            gcc.dg/pr48335-1.c
            gcc.dg/torture/pr67741.c
            gcc.dg/tree-ssa/ssa-dom-thread-10.c
            gcc.dg/tsan/pr88030.c
            gcc.dg/ubsan/float-cast-overflow-atomic.c
            gcc.dg/vect/no-tree-sra-bb-slp-pr50730.c
    
            C++ tests:
            ==========
            g++.dg/opt/alias1.C
            g++.dg/template/koenig6.C
            g++.dg/torture/pr40924.C
            tmpdir-g++.dg-struct-layout-1/t001
    
            Fortran tests:
            ==============
            gfortran.dg/array_constructor_type_22.f03
            gfortran.dg/array_function_6.f90
            gfortran.dg/derived_comp_array_ref_7.f90
            gfortran.dg/elemental_scalar_args_1.f90
            gfortran.dg/elemental_subroutine_1.f90
            gfortran.dg/inline_matmul_5.f90
            gfortran.dg/inline_matmul_8.f90
            gfortran.dg/inline_matmul_9.f90
            gfortran.dg/matmul_bounds_6.f90
            gfortran.dg/operator_1.f90
            gfortran.dg/past_eor.f90
            gfortran.dg/pr101121.f
            gfortran.dg/pr91552.f90
            gfortran.dg/spread_shape_1.f90
            gfortran.dg/typebound_operator_3.f03
            gfortran.dg/value_1.f90
            gfortran.fortran-torture/execute/entry_4.f90
            gfortran.fortran-torture/execute/intrinsic_dotprod.f90
            gfortran.fortran-torture/execute/intrinsic_matmul.f90
    
    2021-09-08  Michael Meissner  <meissner@linux.ibm.com>
    
    gcc/
    
            * config/rs6000/rs6000.c (rs6000_emit_move_si_sf_subreg): Deal
            with SUBREGs of TImode and DImode.

Diff:
---
 gcc/config/rs6000/rs6000.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index b9ebd56c993..7bbf29a3e1c 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -10942,6 +10942,16 @@ rs6000_emit_move_si_sf_subreg (rtx dest, rtx source, machine_mode mode)
 	  return true;
 	}
 
+      /* In case we are given a SUBREG for a larger type, reduce it to
+	 SImode.  */
+      if (mode == SFmode && GET_MODE_SIZE (inner_mode) > 4)
+	{
+	  rtx tmp = gen_reg_rtx (SImode);
+	  emit_move_insn (tmp, gen_lowpart (SImode, source));
+	  emit_insn (gen_movsf_from_si (dest, tmp));
+	  return true;
+	}
+
       if (mode == SFmode && inner_mode == SImode)
 	{
 	  emit_insn (gen_movsf_from_si (dest, inner_source));