Instcombine shouldn't fold these casts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32243 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/2006-12-05-fp-to-int-ext.ll

@@ -0,0 +1,13 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep zext
+
+; Never merge these two conversions, even though it's possible: this is
+; significantly more expensive than the two conversions on some targets
+; and it causes libgcc to be compile __fixunsdfdi into a recursive 
+; function.
+
+
+long %test(double %D) {
+	%A = fptoui double %D to uint
+	%B = zext uint %A to long
+	ret long %B
+}