Revert "Disable InstCombine unsafe folding bitcasts of calls w/ varargs."

This reverts commit d0e277d272.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149647 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/call.ll

@@ -30,6 +30,20 @@ define i32 @test2(i32 %A) {
 }
 
 
+; Resolving this should insert a cast from sbyte to int, following the C 
+; promotion rules.
+define void @test3a(i8, ...) {unreachable }
+
+define void @test3(i8 %A, i8 %B) {
+        call void bitcast (void (i8, ...)* @test3a to void (i8, i8)*)( i8 %A, i8 %B 
+)
+        ret void
+; CHECK: %1 = zext i8 %B to i32
+; CHECK: call void (i8, ...)* @test3a(i8 %A, i32 %1)
+; CHECK: ret void
+}
+
+
 ; test conversion of return value...
 define i8 @test4a() {
         ret i8 0