implement PR4424: 0/x is always 0 for integer division.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73835 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/ConstProp/div-zero.ll

@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i32 0}
+; PR4424
+declare void @ext()
+
+define i32 @foo(i32 %ptr) {
+entry:
+        %zero = sub i32 %ptr, %ptr              ; <i32> [#uses=1]
+        %div_zero = sdiv i32 %zero, ptrtoint (i32* getelementptr (i32* null,
+i32 1) to i32)             ; <i32> [#uses=1]
+        ret i32 %div_zero
+}
+