[flang][runtime] Fix runtime CSHIFT of rank>1 array case of negative shift count

The calculation of the source index was incorrect when a CSHIFT shift
count value is negative, for the implementation of CSHIFT for arrays
with rank >= 2.  (The vector CSHIFT is fine.)

Differential Revision: https://reviews.llvm.org/D127424

diff --git a/flang/runtime/transformational.cpp b/flang/runtime/transformational.cpp
index ac12627..9a01681 100644 (file)
--- a/flang/runtime/transformational.cpp
+++ b/flang/runtime/transformational.cpp
@@ -167,7 +167,7 @@ void RTNAME(Cshift)(Descriptor &result, const Descriptor &source,
     }
     SubscriptValue &sourceDim{sourceAt[dim - 1]};
     sourceDim = dimLB + shiftCount % dimExtent;
-    if (shiftCount < 0) {
+    if (sourceDim < dimLB) {
       sourceDim += dimExtent;
     }
     for (resDim = 1; resDim <= dimExtent; ++resDim) {