From 5c3197fa0bdc505e254859e40d02524b1af3a79c Mon Sep 17 00:00:00 2001
From: peter klausler <pklausler@nvidia.com>
Date: Fri, 5 Apr 2019 12:54:19 -0700
Subject: [PATCH] [flang] Fix implied DO folding with negative strides, add
 test

Original-commit: flang-compiler/f18@2e14b76041c79f5861fb2f912a93572130e08d17
Reviewed-on: https://github.com/flang-compiler/f18/pull/386
Tree-same-pre-rewrite: false
---
 flang/lib/evaluate/fold.cc          | 15 +++++--
 flang/test/semantics/CMakeLists.txt |  1 +
 flang/test/semantics/modfile25.f90  | 64 +++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 flang/test/semantics/modfile25.f90

diff --git a/flang/lib/evaluate/fold.cc b/flang/lib/evaluate/fold.cc
index 6f980e80e96e..2d0d6d1e101e 100644
--- a/flang/lib/evaluate/fold.cc
+++ b/flang/lib/evaluate/fold.cc
@@ -884,10 +884,19 @@ private:
     std::optional<std::int64_t> start{ToInt64(lower)}, end{ToInt64(upper)},
         step{ToInt64(stride)};
     if (start.has_value() && end.has_value() && step.has_value()) {
+      if (*step == 0) {
+        return false;
+      }
       bool result{true};
-      for (std::int64_t &j{context_.StartImpliedDo(iDo.name(), *start)};
-           j <= *end; j += *step) {
-        result &= FoldArray(iDo.values());
+      std::int64_t &j{context_.StartImpliedDo(iDo.name(), *start)};
+      if (*step > 0) {
+        for (; j <= *end; j += *step) {
+          result &= FoldArray(iDo.values());
+        }
+      } else {
+        for (; j >= *end; j += *step) {
+          result &= FoldArray(iDo.values());
+        }
       }
       context_.EndImpliedDo(iDo.name());
       return result;
diff --git a/flang/test/semantics/CMakeLists.txt b/flang/test/semantics/CMakeLists.txt
index c63b9b1d52b2..8b26066ca59c 100644
--- a/flang/test/semantics/CMakeLists.txt
+++ b/flang/test/semantics/CMakeLists.txt
@@ -135,6 +135,7 @@ set(MODFILE_TESTS
   modfile22.f90
   modfile23.f90
   modfile24.f90
+  modfile25.f90
 )
 
 set(LABEL_TESTS
diff --git a/flang/test/semantics/modfile25.f90 b/flang/test/semantics/modfile25.f90
new file mode 100644
index 000000000000..fa3c2df4719c
--- /dev/null
+++ b/flang/test/semantics/modfile25.f90
@@ -0,0 +1,64 @@
+! Copyright (c) 2019, NVIDIA CORPORATION.  All rights reserved.
+!
+! Licensed under the Apache License, Version 2.0 (the "License");
+! you may not use this file except in compliance with the License.
+! You may obtain a copy of the License at
+!
+!     http://www.apache.org/licenses/LICENSE-2.0
+!
+! Unless required by applicable law or agreed to in writing, software
+! distributed under the License is distributed on an "AS IS" BASIS,
+! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+! See the License for the specific language governing permissions and
+! limitations under the License.
+
+! Test compile-time analysis of shapes.
+
+module m1
+  integer(8), parameter :: a0s(:) = shape(3.14159)
+  real :: a1(5,5,5)
+  integer(8), parameter :: a1s(:) = shape(a1)
+  integer(8), parameter :: a1ss(:) = shape(a1s)
+  integer(8), parameter :: a1sss(:) = shape(a1ss)
+  integer(8), parameter :: a1rs(:) = [rank(a1),rank(a1s),rank(a1ss),rank(a1sss)]
+  integer(8), parameter :: a1n(:) = [size(a1),size(a1,1),size(a1,2)]
+  integer(8), parameter :: a1sn(:) = [size(a1s),size(a1ss),size(a1sss)]
+  integer(8), parameter :: ac1s(:) = shape([1])
+  integer(8), parameter :: ac2s(:) = shape([1,2,3])
+  integer(8), parameter :: ac3s(:) = shape([(1,j=1,4)])
+  integer(8), parameter :: ac3bs(:) = shape([(1,j=4,1,-1)])
+  integer(8), parameter :: ac4s(:) = shape([((j,k,j*k,k=1,3),j=1,4)])
+  integer(8), parameter :: ac5s(:) = shape([((0,k=5,1,-2),j=9,2,-3)])
+ contains
+  subroutine subr(x,n1,n2)
+    real, intent(in) :: x(:,:)
+    integer, intent(in) :: n1(3), n2(:)
+    real :: a(:,:,:)
+    a = reshape(x,n1)
+    a = reshape(x,n2(10:30:9)) ! fails if we can't figure out triplet shape
+  end subroutine
+end module m1
+!Expect: m1.mod
+! !mod$ v1 sum:7a360903510189bc
+! module m1
+! integer(8),parameter::a0s(1_8:)=[Integer(8)::]
+! real(4)::a1(1_8:5_8,1_8:5_8,1_8:5_8)
+! integer(8),parameter::a1s(1_8:)=[Integer(8)::5_8,5_8,5_8]
+! integer(8),parameter::a1ss(1_8:)=[Integer(8)::3_8]
+! integer(8),parameter::a1sss(1_8:)=[Integer(8)::1_8]
+! integer(8),parameter::a1rs(1_8:)=[Integer(4)::3_4,1_4,1_4,1_4]
+! integer(8),parameter::a1n(1_8:)=[Integer(8)::125_8,5_8,5_8]
+! integer(8),parameter::a1sn(1_8:)=[Integer(8)::3_8,1_8,1_8]
+! integer(8),parameter::ac1s(1_8:)=[Integer(8)::1_8]
+! integer(8),parameter::ac2s(1_8:)=[Integer(8)::3_8]
+! integer(8),parameter::ac3s(1_8:)=[Integer(8)::4_8]
+! integer(8),parameter::ac3bs(1_8:)=[Integer(8)::4_8]
+! integer(8),parameter::ac4s(1_8:)=[Integer(8)::36_8]
+! integer(8),parameter::ac5s(1_8:)=[Integer(8)::9_8]
+! contains
+! subroutine subr(x,n1,n2)
+! real(4),intent(in)::x(1_8:,1_8:)
+! integer(4),intent(in)::n1(1_8:3_8)
+! integer(4),intent(in)::n2(1_8:)
+! end
+! end
-- 
2.34.1