Test case for CmmOpt inliner on non-single assignment code from new codegen.

The following test creates a nice, inner loop inside a procedure with
the new code generator, which tickles the invariant in CmmOpt that
all temporaries are single assignment and also a register allocator bug.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

testsuite/tests/ghc-regress/codeGen/should_run/all.T

@@ -72,6 +72,7 @@ test('cgrun061', normal, compile_and_run, [''])
 test('cgrun062', normal, compile_and_run, [''])
 test('cgrun063', normal, compile_and_run, [''])
 test('cgrun065', normal, compile_and_run, [''])
+test('cgrun066', normal, compile_and_run, [''])
 
 test('1861', extra_run_opts('0'), compile_and_run, [''])
 

testsuite/tests/ghc-regress/codeGen/should_run/cgrun066.hs

+{-# LANGUAGE MagicHash, BangPatterns #-}
+{-# OPTIONS_GHC -O0 #-}
+
+import Foreign.C
+import Data.Word
+import Foreign.Ptr
+import GHC.Exts
+
+import Control.Exception
+
+hashStr  :: Ptr Word8 -> Int -> Int
+hashStr (Ptr a#) (I# len#) = loop 0# 0#
+   where
+    loop h n | n GHC.Exts.==# len# = I# h
+             | otherwise  = loop h2 (n GHC.Exts.+# 1#)
+          where !c = ord# (indexCharOffAddr# a# n)
+                !h2 = (c GHC.Exts.+# (h GHC.Exts.*# 128#)) `remInt#` 4091#
+
+-- Infinite loops with new code generator + C-- optimizations
+main = do
+    withCStringLen "ff" $ \(ptr, l) -> do
+        print (hashStr (castPtr ptr) l)

testsuite/tests/ghc-regress/codeGen/should_run/cgrun066.stdout

+885