[PATCH] Fortran: ICE in simplification of array expression involving power [PR107680]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

when constant expressions involve parentheses, array constructors,
typespecs, and the power operator (**), we could fail with an ICE
during simplification in arith_power.

Debugging of the testcase showed we call the proper type conversions
needed for the arithmetic operation, but under certain circumstances
we seem to lose the typespec on the way to the invocation of the
simplification.  We then run into unhandled combinations of operand
types.

The attached patch is likely a sort of a band-aid to the problem:
we check the operand types in arith_power, and if we see that a
conversion is (still) needed, we punt and defer the simplification.

AFAICT this is safe.  It does not address a possibly deeply
covered issue in gfortran, which was suspected when analyzing
pr107000.  But as this is elusive, that may be hard to locate
and fix.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald


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From efe9dafabc2e2cc2dab079dfa3be3d09b3471c0f Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Tue, 15 Nov 2022 21:20:20 +0100
Subject: [PATCH] Fortran: ICE in simplification of array expression involving
 power [PR107680]

gcc/fortran/ChangeLog:

	PR fortran/107680
	* arith.cc (arith_power): Check that operands are properly converted
	before attempting to simplify.

gcc/testsuite/ChangeLog:

	PR fortran/107680
	* gfortran.dg/pr107680.f90: New test.
---
 gcc/fortran/arith.cc                   |  7 ++++++
 gcc/testsuite/gfortran.dg/pr107680.f90 | 34 ++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 gcc/testsuite/gfortran.dg/pr107680.f90

diff --git a/gcc/fortran/arith.cc b/gcc/fortran/arith.cc
index fc9224ebc5c..c4ab75b401c 100644
--- a/gcc/fortran/arith.cc
+++ b/gcc/fortran/arith.cc
@@ -845,6 +845,13 @@ arith_power (gfc_expr *op1, gfc_expr *op2, gfc_expr **resultp)
   if (!gfc_numeric_ts (&op1->ts) || !gfc_numeric_ts (&op2->ts))
     return ARITH_INVALID_TYPE;

+  /* The result type is derived from op1 and must be compatible with the
+     result of the simplification.  Otherwise postpone simplification until
+     after operand conversions usually done by gfc_type_convert_binary.  */
+  if ((op1->ts.type == BT_INTEGER && op2->ts.type != BT_INTEGER)
+      || (op1->ts.type == BT_REAL && op2->ts.type == BT_COMPLEX))
+    return ARITH_NOT_REDUCED;
+
   rc = ARITH_OK;
   result = gfc_get_constant_expr (op1->ts.type, op1->ts.kind, &op1->where);

diff --git a/gcc/testsuite/gfortran.dg/pr107680.f90 b/gcc/testsuite/gfortran.dg/pr107680.f90
new file mode 100644
index 00000000000..4ed431eb06f
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr107680.f90
@@ -0,0 +1,34 @@
+! { dg-do compile }
+! { dg-options "-fdump-tree-original" }
+! PR fortran/107680 - ICE in arith_power
+! Contributed by G.Steinmetz
+
+program p
+  real,    parameter :: x(*) = [real    :: ([1])]   **  2.0
+  complex, parameter :: y(*) = [real    :: ([1])]   ** (2.0,1.0)
+  complex, parameter :: z(*) = [complex :: ([1])]   ** (2.0,1.0)
+  complex, parameter :: u(*) = [complex :: ([1.0])] ** (2.0,1.0)
+  complex, parameter :: v(*) = [real    :: ([(1.0,2.0)])] ** (3.0,1.0)
+  complex, parameter :: w(*) = [integer :: ([(1.0,2.0)])] ** (3.0,1.0)
+  print *, [real    :: ([3])]   **  2
+  print *, [real    :: ([3])]   **  2.0
+  print *, [real    :: ([1])]   ** (1.0,2.0)
+  print *, [real    :: ([1.0])] ** (1.0,2.0)
+  print *, [complex :: ([3])]   **  2
+  print *, [complex :: ([3])]   **  2.0
+  print *, [complex :: ([1])]   ** (1.0,2.0)
+  print *, [complex :: ([1.0])] ** (1.0,2.0)
+  print *, [integer :: ([3.0])] **  2
+  print *, [integer :: ([3.0])] **  2.0
+  print *, [integer :: ([1.0])] ** (1.0,2.0)
+  print *, [integer :: ([(1.0,2.0)])] ** (3.0,1.0)
+  print *, v(1)
+  if (u(1) /= 1) stop 1
+  if (v(1) /= 1) stop 2
+  if (w(1) /= 1) stop 3
+  if (x(1) /= 1) stop 4
+  if (y(1) /= 1) stop 5
+  if (z(1) /= 1) stop 6
+end
+
+! { dg-final { scan-tree-dump-not "_gfortran_stop_numeric" "original" } }
--
2.35.3