Reinstate the optimization from r151449 with a fix to not turn 'gep %x' into

'gep null' when the icmp predicate is unsigned (or is signed without inbounds).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151467 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstSimplify/compare.ll

@@ -40,6 +40,69 @@ define i1 @gep2() {
 ; CHECK-NEXT: ret i1 true
 }
 
+; PR11238
+%gept = type { i32, i32 }
+@gepy = global %gept zeroinitializer, align 8
+@gepz = extern_weak global %gept
+
+define i1 @gep3() {
+; CHECK: @gep3
+  %x = alloca %gept, align 8
+  %a = getelementptr %gept* %x, i64 0, i32 0
+  %b = getelementptr %gept* %x, i64 0, i32 1
+  %equal = icmp eq i32* %a, %b
+  ret i1 %equal
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @gep4() {
+; CHECK: @gep4
+  %x = alloca %gept, align 8
+  %a = getelementptr %gept* @gepy, i64 0, i32 0
+  %b = getelementptr %gept* @gepy, i64 0, i32 1
+  %equal = icmp eq i32* %a, %b
+  ret i1 %equal
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @gep5() {
+; CHECK: @gep5
+  %x = alloca %gept, align 8
+  %a = getelementptr inbounds %gept* %x, i64 0, i32 1
+  %b = getelementptr %gept* @gepy, i64 0, i32 0
+  %equal = icmp eq i32* %a, %b
+  ret i1 %equal
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @gep6(%gept* %x) {
+; Same as @gep3 but potentially null.
+; CHECK: @gep6
+  %a = getelementptr %gept* %x, i64 0, i32 0
+  %b = getelementptr %gept* %x, i64 0, i32 1
+  %equal = icmp eq i32* %a, %b
+  ret i1 %equal
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @gep7(%gept* %x) {
+; CHECK: @gep7
+  %a = getelementptr %gept* %x, i64 0, i32 0
+  %b = getelementptr %gept* @gepz, i64 0, i32 0
+  %equal = icmp eq i32* %a, %b
+  ret i1 %equal
+; CHECK: ret i1 %equal
+}
+
+define i1 @gep8(%gept* %x) {
+; CHECK: @gep8
+  %a = getelementptr %gept* %x, i32 1
+  %b = getelementptr %gept* %x, i32 -1
+  %equal = icmp ugt %gept* %a, %b
+  ret i1 %equal
+; CHECK: ret i1 %equal
+}
+
 define i1 @zext(i32 %x) {
 ; CHECK: @zext
   %e1 = zext i32 %x to i64