1*9880d681SAndroid Build Coastguard Worker; RUN: opt < %s -loop-unroll -instcombine -S | FileCheck %s 2*9880d681SAndroid Build Coastguard Worker 3*9880d681SAndroid Build Coastguard Worker; This test is a worst-case scenario for bitreversal/byteswap detection. 4*9880d681SAndroid Build Coastguard Worker; After loop unrolling (the unrolled loop is unreadably large so it has been kept 5*9880d681SAndroid Build Coastguard Worker; rolled here), we have a binary tree of OR operands (as bitreversal detection 6*9880d681SAndroid Build Coastguard Worker; looks straight through shifts): 7*9880d681SAndroid Build Coastguard Worker; 8*9880d681SAndroid Build Coastguard Worker; OR 9*9880d681SAndroid Build Coastguard Worker; | \ 10*9880d681SAndroid Build Coastguard Worker; | LSHR 11*9880d681SAndroid Build Coastguard Worker; | / 12*9880d681SAndroid Build Coastguard Worker; OR 13*9880d681SAndroid Build Coastguard Worker; | \ 14*9880d681SAndroid Build Coastguard Worker; | LSHR 15*9880d681SAndroid Build Coastguard Worker; | / 16*9880d681SAndroid Build Coastguard Worker; OR 17*9880d681SAndroid Build Coastguard Worker; 18*9880d681SAndroid Build Coastguard Worker; This results in exponential runtime. The loop here is 32 iterations which will 19*9880d681SAndroid Build Coastguard Worker; totally hang if we don't deal with this case cleverly. 20*9880d681SAndroid Build Coastguard Worker 21*9880d681SAndroid Build Coastguard Worker@b = common global i32 0, align 4 22*9880d681SAndroid Build Coastguard Worker 23*9880d681SAndroid Build Coastguard Worker; CHECK: define i32 @fn1 24*9880d681SAndroid Build Coastguard Workerdefine i32 @fn1() #0 { 25*9880d681SAndroid Build Coastguard Workerentry: 26*9880d681SAndroid Build Coastguard Worker %b.promoted = load i32, i32* @b, align 4, !tbaa !2 27*9880d681SAndroid Build Coastguard Worker br label %for.body 28*9880d681SAndroid Build Coastguard Worker 29*9880d681SAndroid Build Coastguard Workerfor.body: ; preds = %for.body, %entry 30*9880d681SAndroid Build Coastguard Worker %or4 = phi i32 [ %b.promoted, %entry ], [ %or, %for.body ] 31*9880d681SAndroid Build Coastguard Worker %i.03 = phi i32 [ 0, %entry ], [ %inc, %for.body ] 32*9880d681SAndroid Build Coastguard Worker %shr = lshr i32 %or4, 1 33*9880d681SAndroid Build Coastguard Worker %or = or i32 %shr, %or4 34*9880d681SAndroid Build Coastguard Worker %inc = add nuw nsw i32 %i.03, 1 35*9880d681SAndroid Build Coastguard Worker %exitcond = icmp eq i32 %inc, 32 36*9880d681SAndroid Build Coastguard Worker br i1 %exitcond, label %for.end, label %for.body 37*9880d681SAndroid Build Coastguard Worker 38*9880d681SAndroid Build Coastguard Workerfor.end: ; preds = %for.body 39*9880d681SAndroid Build Coastguard Worker store i32 %or, i32* @b, align 4, !tbaa !2 40*9880d681SAndroid Build Coastguard Worker ret i32 undef 41*9880d681SAndroid Build Coastguard Worker} 42*9880d681SAndroid Build Coastguard Worker 43*9880d681SAndroid Build Coastguard Workerattributes #0 = { norecurse nounwind ssp uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="core2" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+ssse3" "unsafe-fp-math"="false" "use-soft-float"="false" } 44*9880d681SAndroid Build Coastguard Worker 45*9880d681SAndroid Build Coastguard Worker!llvm.module.flags = !{!0} 46*9880d681SAndroid Build Coastguard Worker!llvm.ident = !{!1} 47*9880d681SAndroid Build Coastguard Worker 48*9880d681SAndroid Build Coastguard Worker!0 = !{i32 1, !"PIC Level", i32 2} 49*9880d681SAndroid Build Coastguard Worker!1 = !{!"clang version 3.8.0 (http://llvm.org/git/clang.git eb70f4e9cc9a4dc3dd57b032fb858d56b4b64a0e)"} 50*9880d681SAndroid Build Coastguard Worker!2 = !{!3, !3, i64 0} 51*9880d681SAndroid Build Coastguard Worker!3 = !{!"int", !4, i64 0} 52*9880d681SAndroid Build Coastguard Worker!4 = !{!"omnipotent char", !5, i64 0} 53*9880d681SAndroid Build Coastguard Worker!5 = !{!"Simple C/C++ TBAA"} 54