Roger Sayle - [FORTRAN PATCH] Eliminate temporary when passing constant array co (original) (raw)

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[FORTRAN PATCH] Eliminate temporary when passing constant array constructors as arguments

• From: "Roger Sayle"
• To: fortran at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
• Date: Thu, 1 Feb 2007 13:01:43 -0700 (MST)
• Subject: [FORTRAN PATCH] Eliminate temporary when passing constant array constructors as arguments

The following patch to the gfortran front-end improves the way that array constructors are passed as function arguments. The current implementation copies the entire array constructor into a temporary array to allow the temporary array's descriptor to be passed to the function. In the patch below we improve this for constant array constructors (of non-character types) by creating a descriptor for the array constructor (much like we do for regular array variables) and pass that. As with regular array variables this avoids any copying loops.

When combined with my previous patch to correctly detect dependencies on array constructors we can now expand the following code without any array temporaries.

integer :: x(6)

x = cshift((/ 1, 2, 3, 4, 5, 6/), 2) end

With these two pending patches we get:

int4 x[6];
static int4 C.1362 = 2;
struct array1_int4 parm.2;
static int4 A.1[6] = {1, 2, 3, 4, 5, 6};
struct array1_int4 parm.0;

parm.0.dtype = 265;
parm.0.dim[0].lbound = 1;
parm.0.dim[0].ubound = 6;
parm.0.dim[0].stride = 1;
parm.0.data = (void *) &x[0];
parm.0.offset = 0;
parm.2.dtype = 265;
parm.2.dim[0].lbound = 1;
parm.2.dim[0].ubound = 6;
parm.2.dim[0].stride = 1;
parm.2.data = (void *) &A.1[0];
parm.2.offset = 0;
_gfortran_cshift0_4 (&parm.0, &parm.2, &C.1362, 0B);

Compare this to current mainline where we generate:

int4 x[6];
int4 A.5[6];
struct array1_int4 atmp.4;
static int4 C.1364 = 2;
int4 A.2[6];
struct array1_int4 atmp.1;
static int4 A.0[6] = {1, 2, 3, 4, 5, 6};

atmp.1.dtype = 265;
atmp.1.dim[0].stride = 1;
atmp.1.dim[0].lbound = 0;
atmp.1.dim[0].ubound = 5;
atmp.1.data = (void *) &A.2;
atmp.1.offset = 0;
{
  int8 S.3;

  S.3 = 0;
  while (1)
    {
      if (S.3 > 5) goto L.1;
      (*(int4[0:] *) atmp.1.data)[S.3] = A.0[S.3];
      S.3 = S.3 + 1;
    }
  L.1:;
}
atmp.4.dtype = 265;
atmp.4.dim[0].stride = 1;
atmp.4.dim[0].lbound = 0;
atmp.4.dim[0].ubound = 5;
atmp.4.data = (void *) &A.5;
atmp.4.offset = 0;
_gfortran_cshift0_4 (&atmp.4, &atmp.1, &C.1364, 0B);
{
  int8 S.6;

  S.6 = 0;
  while (1)
    {
      if (S.6 > 5) goto L.2;
      x[NON_LVALUE_EXPR <S.6>] = (*(int4[0:] *) atmp.4.data)[S.6];
      S.6 = S.6 + 1;
    }
  L.2:;
}

The following patch has been tested on x86_64-unknown-linux-gnu with a full "make bootstrap", all default languages including gfortran, and regression tested with a top-level "make -k check" with no new failures.

Ok for mainline?

2007-02-01 Roger Sayle roger@eyesopen.com

    * trans-array.c (gfc_conv_expr_descriptor): We don't need to use
    a temporary array to pass a constant non-chracter array constructor.
    Generalize the descriptor generation code to handle scalarizer
    "info" without an array reference.

Roger

Attachment:patchf3.txt
Description: Text document

• Follow-Ups:
  • Re: [FORTRAN PATCH] Eliminate temporary when passing constant array constructors as arguments
    * From: Steve Kargl
  • Re: [FORTRAN PATCH] Eliminate temporary when passing constant array constructors as arguments
    * From: Jack Howarth