Fix a problem with mips16 stubs when calls are transformed during

tail call optimization. Some more work may be needed for indirect
calls but this patch fixes the current regression in Prolangc++/trees.
S2 optimization as part of the general cleanup and optimization
of prolog and epilog was not saving S2 in this case and needed to.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197630 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/Mips/tail16.ll

@@ -0,0 +1,20 @@
+; RUN: llc -mtriple=mipsel-linux-gnu -march=mipsel -mcpu=mips16 -soft-float -mips16-hard-float -relocation-model=pic   < %s | FileCheck %s 
+
+; Function Attrs: nounwind optsize
+define float @h()  {
+entry:
+  %call = tail call float bitcast (float (...)* @g to float ()*)() 
+  ret float %call
+; CHECK:	.ent	h
+; CHECK: 	save	$16, $ra, $18, 32
+; CHECK: 	lw	${{[0-9]+}}, %got(__mips16_call_stub_sf_0)(${{[0-9]+}})
+; CHECK: 	restore	$16, $ra, $18, 32
+; CHECK: 	.end	h
+}
+
+; Function Attrs: optsize
+declare float @g(...) 
+
+
+
+