new test case for PR1280

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35401 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/2007-03-27-PR1280.ll

@@ -0,0 +1,15 @@
+; PR1280 - we should be able to reduce this function to a trunc/sext but it
+;          would involve using a bit width (24) that doesn't match a size that
+;          the back end can handle. This test makes sure that such a transform
+;          is not done. It should be removed when code gen supports "funny"
+;          bit widths.
+
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep 'add i49.*-8388608'
+
+define i49 @test5(i49 %x) {
+        ;; If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
+        %X = and i49 %x, 16777215                     ; 0x0000000ffffff
+        %tmp.2 = xor i49 %X, 8388608                  ; 0x0000000800000
+        %tmp.4 = add i49 %tmp.2, -8388608             ; 0x1FFFFFF800000
+        ret i49 %tmp.4
+}