Hello world,
what it says in the ChangeLog entry. Regression-tested (and the test
case makes sure there is no wrong-code regression).
OK for trunk?
Best regards
Thomas
Rewrite (-1.0)**n to (real) (1 - (n & 1) << 1)).
The problem was that the optimization done for PR 57073 uses powi and
friends, so it only applied to default integer exponent. The test
case has an integer(kind=8) exponent, which is is calculated by
calling a gfortran library function.
There are two possible approaches: One would be to convert all
integer types to default integer (because only the lowest-value
bit matters to the result) and call the right __builtin_powi function.
However, the generated code is suboptimal, see PR 125919. I therefore
chose the variant which currently generates the best code.
This requires the change to the power_6.f90 test case.
gcc/fortran/ChangeLog:
PR fortran/125914
* trans-expr.cc (gfc_conv_power_op): Rewrite (-1.0)**n into
(real) (1 - (n & 1) << 1)).
gcc/testsuite/ChangeLog:
PR fortran/125914
* gfortran.dg/power_6.f90: Remove scans for powi.
* gfortran.dg/power_10.f90: New test.
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 8acee12e9c2..a1aa529a43d 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -4026,6 +4026,26 @@ gfc_conv_power_op (gfc_se * se, gfc_expr * expr)
case BT_REAL:
/* Use builtins for real ** int4. */
+
+ if (real_minus_onep (lse.expr))
+ {
+ /* (-1.0)**n is (real) (1 - ((n & 1) << 1)), see the integer case
+ above. */
+
+ tree lhs_type, rhs_type;
+ tree tmp;
+ lhs_type = TREE_TYPE (lse.expr);
+ rhs_type = TREE_TYPE (rse.expr);
+ tmp = fold_build2_loc (input_location, BIT_AND_EXPR, rhs_type,
+ rse.expr, build_int_cst (rhs_type, 1));
+ tmp = fold_build2_loc (input_location, LSHIFT_EXPR, rhs_type,
+ tmp, build_int_cst (rhs_type, 1));
+ tmp = fold_build2_loc (input_location, MINUS_EXPR, rhs_type,
+ build_int_cst (rhs_type, 1), tmp);
+ se->expr = fold_convert (lhs_type, tmp);
+ return;
+ }
+
if (ikind == 0)
{
switch (kind)
diff --git a/gcc/testsuite/gfortran.dg/power_10.f90 b/gcc/testsuite/gfortran.dg/power_10.f90
new file mode 100644
index 00000000000..8f0a8db3fee
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/power_10.f90
@@ -0,0 +1,85 @@
+! { dg-do run }
+! PR fortran/125914 - optimize 1.0*n
+! { dg-additional-options "-fdump-tree-original" }
+
+program memain
+ implicit none
+ integer, parameter :: n = 16
+ integer (kind=1), dimension(n) :: i1
+ integer (kind=2), dimension(n) :: i2
+ integer (kind=4), dimension(n) :: i4 = &
+ [6, 5, 4, 4, 10, 8, 12, 8, 9, 4, 8, 11, 12, 10, 3, 12]
+ integer (kind=8), dimension(n) :: i8
+ real (kind=8), dimension(n) :: r8 = &
+ [0.996104819512799_8, 0.245675968329691_8, &
+ 0.0303468106690589_8, 0.0240992716571487_8, &
+ 0.0354064316729468_8, 0.275774313901932_8, &
+ 0.544792948166924_8, 0.445879110979491_8, &
+ 0.241491365544482_8, 0.0954139664143259_8, &
+ 0.0109187857324577_8, 0.0946393553679743_8, &
+ 0.140308573675276_8, 0.353858089853078_8, &
+ 0.879882896668272_8, 0.818438744841301_8]
+
+ real (kind=4), dimension(n) :: r4
+
+ integer(kind=8) :: i
+ real (kind=8) :: s8
+ real (kind=4) :: s4
+
+ i1 = i4
+ i2 = i4
+ i8 = i4
+
+ s8 = 0
+ do i=1,n
+ s8 = s8 + r8(i)*(-1.0_8)**i1(i)
+ end do
+ if (s8 /= 2.3096522811663198_8) stop 1
+
+ s8 = 0
+ do i=1,n
+ s8 = s8 + r8(i)*(-1.0_8)**i2(i)
+ end do
+ if (s8 /= 2.3096522811663198_8) stop 2
+
+ s8 = 0
+ do i=1,n
+ s8 = s8 + r8(i)*(-1.0_8)**i4(i)
+ end do
+ if (s8 /= 2.3096522811663198_8) stop 3
+
+ s8 = 0
+ do i=1,n
+ s8 = s8 + r8(i)*(-1.0_8)**i8(i)
+ end do
+ if (s8 /= 2.3096522811663198_8) stop 4
+
+ r4 = r8
+
+ s4 = 0
+ do i=1,n
+ s4 = s4 + r4(i)*(-1.0)**i1(i)
+ end do
+ if (s4 /= 2.30965209) stop 11
+
+ s4 = 0
+ do i=1,n
+ s4 = s4 + r4(i)*(-1.0)**i2(i)
+ end do
+ if (s4 /= 2.30965209) stop 12
+
+ s4 = 0
+ do i=1,n
+ s4 = s4 + r4(i)*(-1.0)**i4(i)
+ end do
+ if (s4 /= 2.30965209) stop 13
+
+ s4 = 0
+ do i=1,n
+ s4 = s4 + r4(i)*(-1.0)**i8(i)
+ end do
+ if (s4 /= 2.30965209) stop 14
+
+end program memain
+! { dg-final { scan-tree-dump-not "_gfortran_pow" "original" } }
+! { dg-final { scan-tree-dump-not "__builtin_powi" "original" } }
diff --git a/gcc/testsuite/gfortran.dg/power_6.f90 b/gcc/testsuite/gfortran.dg/power_6.f90
index 7d3a1f412f3..4f504b7af75 100644
--- a/gcc/testsuite/gfortran.dg/power_6.f90
+++ b/gcc/testsuite/gfortran.dg/power_6.f90
@@ -10,5 +10,3 @@ real function f(k)
end
! { dg-final { scan-tree-dump-not "__builtin_powif" "optimized" } }
-! { dg-final { scan-tree-dump "powi_cond_\[0-9\] = k_\[0-9\]\\(D\\) & 1;" "optimized" } }
-! { dg-final { scan-tree-dump "powi_\[0-9\] = powi_cond_\[0-9\] \\? -1.0e\\+0 : 1.0e\\+0;" "optimized" } }
