1; RUN: opt -early-cse -S %s | FileCheck %s 2 3%mystruct = type { i32 } 4 5; @var is global so that *every* GEP argument is Constant. 6@var = external global %mystruct 7 8; Control flow is to make the dominance tree consider the final icmp before it 9; gets to simplify the purely constant one (%tst). Since that icmp uses the 10; select that gets considered next. Finally the select simplification looks at 11; the %tst icmp and we don't want it to speculate about what happens if "i32 0" 12; is actually "i32 1", broken universes are automatic UB. 13; 14; In this case doing the speculation would create an invalid GEP(@var, 0, 1) and 15; crash. 16 17define i1 @test_constant_speculation() { 18; CHECK-LABEL: define i1 @test_constant_speculation 19entry: 20 br i1 undef, label %end, label %select 21 22select: 23; CHECK: select: 24; CHECK-NOT: icmp 25; CHECK-NOT: getelementptr 26; CHECK-NOT: select 27 28 %tst = icmp eq i32 1, 0 29 %elt = getelementptr %mystruct, %mystruct* @var, i64 0, i32 0 30 %sel = select i1 %tst, i32* null, i32* %elt 31 br label %end 32 33end: 34; CHECK: end: 35; CHECK: %tmp = phi i32* [ null, %entry ], [ getelementptr inbounds (%mystruct, %mystruct* @var, i64 0, i32 0), %select ] 36 %tmp = phi i32* [null, %entry], [%sel, %select] 37 %res = icmp eq i32* %tmp, null 38 ret i1 %res 39} 40