add a test for #5149

The only way I could ticke this with a small program was to write it
directly in .cmm (urgh).

tests/ghc-regress/codeGen/should_run/5149.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE MagicHash,GHCForeignImportPrim,UnliftedFFITypes #-}
+module Main where
+
+import GHC.Exts
+
+foreign import prim "f5149" f :: Int# -> Int# -> Double# -> Int#
+
+main = print (I# (f 1# 2# 1.0##))

tests/ghc-regress/codeGen/should_run/5149.stdout

@@ -0,0 +1 @@
+1

tests/ghc-regress/codeGen/should_run/5149_cmm.cmm

@@ -0,0 +1,29 @@
+#include "Cmm.h"
+
+/* This code is carefully arranged to tickle the bug reported in #5149 */
+f5149
+{
+    D_ z;
+
+    z = D1;
+
+    W_ x,y;
+    x = R1;
+    y = R2;
+
+    if (x > y) {
+       goto a; /* this jump is shortcutted to g5149 */
+    }  else {
+       goto b;
+    }
+
+  a:
+    jump g5149;
+  b:
+    RET_N(TO_W_(%f2i32(z)));
+}
+
+g5149
+{
+    jump %ENTRY_CODE(Sp(0));
+}

tests/ghc-regress/codeGen/should_run/Makefile

@@ -1,3 +1,10 @@
 TOP=../../../..
 include $(TOP)/mk/boilerplate.mk
 include $(TOP)/mk/test.mk
+
+.PHONY: 5149
+5149:
+	$(RM) 5149_cmm.o 5149.o 5149.hi 5149$(exeext)
+	$(TEST_HC) -v0 -O -c 5149_cmm.cmm
+	$(TEST_HC) -v0 --make -O 5149.hs 5149_cmm.o -o 5149$(exeext)
+	./5149

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

@@ -84,3 +84,6 @@ test('3561', normal, compile_and_run, [''])
 test('3677', extra_run_opts('+RTS -K8k -RTS'), compile_and_run, [''])
 test('4441', normal, compile_and_run, [''])
 
+test('5149', [ extra_clean(['5149.o', '5149.hi', '5149_cmm.o', '5149']) ],
+             run_command,
+             ['$MAKE -s --no-print-directory 5149'])