TeamHeptaMirrors/gcc
1
0
Fork 1
mirror of https://github.com/gcc-mirror/gcc.git synced 2026-05-06 14:59:39 +02:00
Code Issues Packages Projects Releases Wiki Activity

vect-generic: Fix up expand_vector_mult [PR123656]

Browse Source 
The alg_sub_factor handling in expand_vector_mult had the arguments
reversed.
As documented in expmed.h, the algorithms should be
   These are the operations:
   alg_zero             total := 0;
   alg_m                total := multiplicand;
   alg_shift            total := total * coeff
   alg_add_t_m2         total := total + multiplicand * coeff;
   alg_sub_t_m2         total := total - multiplicand * coeff;
   alg_add_factor       total := total * coeff + total;
   alg_sub_factor       total := total * coeff - total;
   alg_add_t2_m         total := total * coeff + multiplicand;
   alg_sub_t2_m         total := total * coeff - multiplicand;

   The first operand must be either alg_zero or alg_m.  */
So, alg_sub_factor should be identical to alg_sub_t2_m with the
difference that one subtracts accumulator and the other subtracts
op0.  I went through all the other ones and they seem to match
the description except for alg_sub_factor and tree-vect-patterns.cc
seems to be fully correct.  expand_vector_mult at times has
pretty random order of PLUS_EXPR arguments, but that is a commutative
operation, so makes no difference.

Furthermore, I saw weird formatting in the alg_add_t_m2 case, so fixed
that too.

2026-01-19  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/123656
	* tree-vect-generic.cc (expand_vector_mult): Fix up alg_sub_factor
	handling.  Fix up formatting in alg_add_t_m2 handling.

	* gcc.dg/pr123656.c: New test.
This commit is contained in:
Jakub Jelinek
2026-01-19 09:46:36 +01:00
committed by Jakub Jelinek
parent 34039b22ad
commit d718835414
2 changed files with 24 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
gcc/testsuite/gcc.dg/pr123656.c Normal file
View File

@@ -0,0 +1,21 @@
/* PR tree-optimization/123656 */
/* { dg-do run } */
/* { dg-options "-Og -Wno-psabi" } */
#define C 210
typedef __attribute__((__vector_size__ (2))) unsigned char V;
V
foo (V v)
{
return v * C;
}
int
main ()
{
V x = foo ((V) {1, 1});
if (x[0] != C || x[1] != C)
__builtin_abort ();
}

6
gcc/tree-vect-generic.cc
View File

@@ -643,9 +643,9 @@ expand_vector_mult (gimple_stmt_iterator *gsi, tree type, tree op0,
LSHIFT_EXPR);
break;
case alg_add_t_m2:
tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
accumulator = gimplify_build2 (gsi, PLUS_EXPR, vectype, tmp_var,
accumulator);
accumulator);
break;
case alg_sub_t_m2:
tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
@@ -674,7 +674,7 @@ expand_vector_mult (gimple_stmt_iterator *gsi, tree type, tree op0,
tmp_var = add_shift (gsi, vectype, accumulator, shifts,
LSHIFT_EXPR);
accumulator = gimplify_build2 (gsi, MINUS_EXPR, vectype,
accumulator, tmp_var);
tmp_var, accumulator);
break;
default:
gcc_unreachable ();