Fix stackleft on nvc.

src/qthread.c

@@ -1294,7 +1294,7 @@ size_t API_FUNC qthread_stackleft(void) { /*{{{ */
   qthread_t const *f = qthread_internal_self();
 
   if ((f != NULL) && (f->rdata->stack != NULL)) {
-#ifdef __INTEL_COMPILER
+#if defined(__INTEL_COMPILER)
     size_t current = (size_t)&f;
 #else
     size_t current = (size_t)__builtin_frame_address(0);

test/basics/qthread_stackleft.c

@@ -12,9 +12,14 @@ static aligned_t x = 0;
 
 static aligned_t alldone;
 
+// The structure of this test is fairly trivial so we have to use
+// various compiler-specific stuff to prevent TCO from kicking in
+// and preventing us from testing that the stack behaves as expected.
 #ifdef __clang__
 #define STACKLEFT_NOINLINE __attribute__((optnone))
-#elif __GNUC__
+#elif defined(__NVCOMPILER)
+#define STACKLEFT_NOINLINE __attribute__((noinline))
+#elif defined(__GNUC__)
 #define STACKLEFT_NOINLINE __attribute__((optimize(0)))
 #else
 #define STACKLEFT_NOINLINE
@@ -37,6 +42,12 @@ static aligned_t alldone;
 
 static STACKLEFT_NOINLINE size_t thread2(size_t left, size_t depth) {
   size_t foo = qthread_stackleft();
+
+#if defined(__NVCOMPILER)
+  // nvc doesn't currently support enough attributes/pragmas to prevent TCO
+  // here. This still works though.
+  asm volatile("" : : "g"(&depth) : "memory");
+#endif
   iprintf("leveli%i: %zu bytes left\n", (int)depth, foo);
   assert(foo < left);
   if (depth < 5) { thread2(foo, depth + 1); }