Dear all,
as reported, the Fortran standard requires all actual argument
expressions to be evaluated (e.g. F2018:15.5.3).
There were two cases for intrinsic MERGE where we failed to do so:
- non-constant mask; Steve provided the patch
- constant scalar mask; we need to be careful to simplify only if
the argument on the "other" path is known to be constant so that
it does not have side-effects and can be immediately removed.
The latter change needed a correction of a sub-test of testcase
merge_init_expr_2.f90, which should not have been simplified
the way the original author assumed. I decided to modify the
test in such way that simplification is valid and provides
the expect pattern.
Regtested on x86_64-pc-linux-gnu. OK for mainline?
Thanks,
Harald
From 0f6058937c04a7af5e6dcfa173648149c24f08df Mon Sep 17 00:00:00 2001
From: Harald Anlauf
Date: Mon, 28 Nov 2022 20:43:02 +0100
Subject: [PATCH] Fortran: intrinsic MERGE shall use all its arguments
[PR107874]
gcc/fortran/ChangeLog:
PR fortran/107874
* simplify.cc (gfc_simplify_merge): When simplifying MERGE with a
constant scalar MASK, ensure that arguments TSOURCE and FSOURCE are
either constant or will be evaluated.
* trans-intrinsic.cc (gfc_conv_intrinsic_merge): Evaluate arguments
before generating conditional expression.
gcc/testsuite/ChangeLog:
PR fortran/107874
* gfortran.dg/merge_init_expr_2.f90: Adjust code to the corrected
simplification.
* gfortran.dg/merge_1.f90: New test.
Co-authored-by: Steven G. Kargl
---
gcc/fortran/simplify.cc | 17 ++-
gcc/fortran/trans-intrinsic.cc| 3 ++
gcc/testsuite/gfortran.dg/merge_1.f90 | 49 +++
.../gfortran.dg/merge_init_expr_2.f90 | 3 +-
4 files changed, 70 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gfortran.dg/merge_1.f90
diff --git a/gcc/fortran/simplify.cc b/gcc/fortran/simplify.cc
index 9c2fea8c5f2..b6184181f26 100644
--- a/gcc/fortran/simplify.cc
+++ b/gcc/fortran/simplify.cc
@@ -4913,7 +4913,22 @@ gfc_simplify_merge (gfc_expr *tsource, gfc_expr *fsource, gfc_expr *mask)
if (mask->expr_type == EXPR_CONSTANT)
{
- result = gfc_copy_expr (mask->value.logical ? tsource : fsource);
+ /* The standard requires evaluation of all function arguments.
+ Simplify only when the other dropped argument (FSOURCE or TSOURCE)
+ is a constant expression. */
+ if (mask->value.logical)
+ {
+ if (!gfc_is_constant_expr (fsource))
+ return NULL;
+ result = gfc_copy_expr (tsource);
+ }
+ else
+ {
+ if (!gfc_is_constant_expr (tsource))
+ return NULL;
+ result = gfc_copy_expr (fsource);
+ }
+
/* Parenthesis is needed to get lower bounds of 1. */
result = gfc_get_parentheses (result);
gfc_simplify_expr (result, 1);
diff --git a/gcc/fortran/trans-intrinsic.cc b/gcc/fortran/trans-intrinsic.cc
index bb938026828..93426981bac 100644
--- a/gcc/fortran/trans-intrinsic.cc
+++ b/gcc/fortran/trans-intrinsic.cc
@@ -7557,6 +7557,9 @@ gfc_conv_intrinsic_merge (gfc_se * se, gfc_expr * expr)
&se->pre);
se->string_length = len;
}
+ tsource = gfc_evaluate_now (tsource, &se->pre);
+ fsource = gfc_evaluate_now (fsource, &se->pre);
+ mask = gfc_evaluate_now (mask, &se->pre);
type = TREE_TYPE (tsource);
se->expr = fold_build3_loc (input_location, COND_EXPR, type, mask, tsource,
fold_convert (type, fsource));
diff --git a/gcc/testsuite/gfortran.dg/merge_1.f90 b/gcc/testsuite/gfortran.dg/merge_1.f90
new file mode 100644
index 000..abbc2276b1c
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/merge_1.f90
@@ -0,0 +1,49 @@
+! { dg-do run }
+! PR fortran/107874 - merge not using all its arguments
+! Contributed by John Harper
+
+program testmerge9
+ implicit none
+ integer :: i
+ logical :: x(2) = (/.true., .false./)
+ logical :: called(2)
+
+ ! At run-time all arguments shall be evaluated
+ do i = 1,2
+ called = .false.
+ print *, merge (tstuff(), fstuff(), x(i))
+ if (any (.not. called)) stop 1
+ end do
+
+ ! Compile-time simplification shall not drop non-constant args
+ called = .false.
+ print *, merge (tstuff(),fstuff(),.true.)
+ if (any (.not. called)) stop 2
+ called = .false.
+ print *, merge (tstuff(),fstuff(),.false.)
+ if (any (.not. called)) stop 3
+ called = .false.
+ print *, merge (tstuff(),.false.,.true.)
+ if (any (called .neqv. [.true.,.false.])) stop 4
+ called = .false.
+ print *, merge (tstuff(),.false.,.false.)
+ if (any (called .neqv. [.true.,.false.])) stop 5
+ called = .false.
+ print *, merge (.true.,fstuff(),.true.)
+ if (any (called .neqv. [.false.,.true.])) stop 6
+ called = .false.
+ print *, merge (.true.,fstuff(),.false.)
+ if (any (called .neqv. [.false.,.true.])) stop 7
+contains
+ logical function tstuff()
+print *,'tstuff'
+tstuff = .true.
+called(1) = .true.
+ end function tstuff
+
+ logical function fstuff()
+print *,'fstuff'
+fs
