[PATCH] D119373: [flang] Make folding of LEN less aggressive

[Eric Schweitz via Phabricator via llvm-commits]

schweitz created this revision.
schweitz added reviewers: clementval, jeanPerier, PeteSteinfeld, mleair, vdonaldson, svedanayagam, klausler.
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Folding in the front end was replacing calls to LEN and dropping
arguments even in situations where the arguments are required to compute
the LEN value at runtime.

      

Add tests.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119373

Files:
  flang/lib/Evaluate/fold-integer.cpp
  flang/test/Evaluate/rewrite01.f90


Index: flang/test/Evaluate/rewrite01.f90
===================================================================
--- flang/test/Evaluate/rewrite01.f90
+++ flang/test/Evaluate/rewrite01.f90
@@ -76,4 +76,33 @@
   !CHECK: PRINT *, 1_4
   print *, lbound(returns_array_3(), dim=1)
 end subroutine
+
+subroutine len_test(a,b, c, d)
+  character(*) :: a, b
+  external b
+  character(10) :: c, d
+  external d
+
+  !CHECK: PRINT *, len(a)
+  print *, len(a)
+  !CHECK: PRINT *, 5_4
+  print *, len(a(1:5))
+  !CHECK: PRINT *, len(b(a))
+  print *, len(b(a))
+  !CHECK: PRINT *, len(b(a)//a)
+  print *, len(b(a) // a)
+  !CHECK: PRINT *, 10_4
+  print *, len(c)
+  !CHECK: PRINT *, len(c(int(i,kind=8):int(j,kind=8)))
+  print *, len(c(i:j))
+  !CHECK: PRINT *, 5_4
+  print *, len(c(1:5))
+  !CHECK: PRINT *, 10_4
+  print *, len(d(c))
+  !CHECK: PRINT *, 20_4
+  print *, len(d(c) // c)
+  !CHECK: PRINT *, 0_4
+  print *, len(a(10:4))
+end subroutine len_test
+
 end module
Index: flang/lib/Evaluate/fold-integer.cpp
===================================================================
--- flang/lib/Evaluate/fold-integer.cpp
+++ flang/lib/Evaluate/fold-integer.cpp
@@ -677,7 +677,11 @@
       return std::visit(
           [&](auto &kx) {
             if (auto len{kx.LEN()}) {
-              return Fold(context, ConvertToType<T>(*std::move(len)));
+              if (IsConstantExpr(len)) {
+                return Fold(context, ConvertToType<T>(*std::move(len)));
+              } else {
+                return Expr<T>{std::move(funcRef)};
+              }
             } else {
               return Expr<T>{std::move(funcRef)};
             }


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