[PATCH] RISC-V: Fix splitter for 32-bit AND on 64-bit target.

[Richard Biener]

On Tue, 16 Jul 2019, Kito Cheng wrote:

> Hi
> 
> I'd like to back port this patch to GCC 8 and 9, should I send another
> patch mail or just wait ack from release manager?

Looks OK to backport since it only affects RISC-V and that's neither
a primary nor secondary arch and this looks like a wrong-code issue.

Richard.

> 
> 
> On Mon, Jul 8, 2019 at 6:48 PM Jim Wilson <jimw@sifive.com> wrote:
> >
> > Fixes github.com/riscv/riscv-gcc issue #161.  We were accidentally using
> > BITS_PER_WORD to compute shift counts when we should have been using the
> > bitsize of the operand modes.  This was wrong when we had an SImode shift
> > and a 64-bit target.
> >
> > Tested with 32-bit elf and 64-bit linux cross compiler builds and checks.
> > There were no regressions.  The new test fails without the patch and works
> > with the patch.
> >
> > Committed.
> >
> > Jim
> >
> >         Andrew Waterman  <andrew@sifive.com>
> >         gcc/
> >         * config/riscv/riscv.md (lshrsi3_zero_extend_3+1): Use operands[1]
> >         bitsize instead of BITS_PER_WORD.
> >         gcc/testsuite/
> >         * gcc.target/riscv/shift-shift-2.c: Add one more test.
> > ---
> >  gcc/config/riscv/riscv.md                      |  5 +++--
> >  gcc/testsuite/gcc.target/riscv/shift-shift-2.c | 16 ++++++++++++++--
> >  2 files changed, 17 insertions(+), 4 deletions(-)
> >
> > diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
> > index 0f4626656d6..78260fcf6fd 100644
> > --- a/gcc/config/riscv/riscv.md
> > +++ b/gcc/config/riscv/riscv.md
> > @@ -1776,10 +1776,11 @@
> >    (set (match_dup 0)
> >         (lshiftrt:GPR (match_dup 0) (match_dup 2)))]
> >  {
> > -  operands[2] = GEN_INT (BITS_PER_WORD
> > +  /* Op2 is a VOIDmode constant, so get the mode size from op1.  */
> > +  operands[2] = GEN_INT (GET_MODE_BITSIZE (GET_MODE (operands[1]))
> >                          - exact_log2 (INTVAL (operands[2]) + 1));
> >  })
> > -
> > +
> >  ;; Handle AND with 0xF...F0...0 where there are 32 to 63 zeros.  This can be
> >  ;; split into two shifts.  Otherwise it requires 3 instructions: li, sll, and.
> >  (define_split
> > diff --git a/gcc/testsuite/gcc.target/riscv/shift-shift-2.c b/gcc/testsuite/gcc.target/riscv/shift-shift-2.c
> > index 3f07e7776e7..10a5bb728be 100644
> > --- a/gcc/testsuite/gcc.target/riscv/shift-shift-2.c
> > +++ b/gcc/testsuite/gcc.target/riscv/shift-shift-2.c
> > @@ -25,5 +25,17 @@ sub4 (unsigned long i)
> >  {
> >    return (i << 52) >> 52;
> >  }
> > -/* { dg-final { scan-assembler-times "slli" 4 } } */
> > -/* { dg-final { scan-assembler-times "srli" 4 } } */
> > +
> > +unsigned int
> > +sub5 (unsigned int i)
> > +{
> > +  unsigned int j;
> > +  j = i >> 24;
> > +  j = j * (1 << 24);
> > +  j = i - j;
> > +  return j;
> > +}
> > +/* { dg-final { scan-assembler-times "slli" 5 } } */
> > +/* { dg-final { scan-assembler-times "srli" 5 } } */
> > +/* { dg-final { scan-assembler-times "slliw" 1 } } */
> > +/* { dg-final { scan-assembler-times "srliw" 1 } } */
> > --
> > 2.17.1
> >
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)