test/FrontendC/2008-01-25-ByValReadNone.c

   1 // RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | not grep readonly
   2 // RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | not grep readnone
   3
   4
   5 // The struct being passed byval means that we cannot mark the
   6 // function readnone.  Readnone would allow stores to the arg to
   7 // be deleted in the caller.  We also don't allow readonly since
   8 // the callee might write to the byval parameter.  The inliner
   9 // would have to assume the worse and introduce an explicit
  10 // temporary when inlining such a function, which is costly for
  11 // the common case in which the byval argument is not written.
  12 struct S { int A[1000]; };
  13 int __attribute__ ((const)) f(struct S x) { x.A[1] = 0; return x.A[0]; }
  14 int g(struct S x) __attribute__ ((pure));
  15 int h(struct S x) { return g(x); }