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llvm-mirror/test/Analysis/ScalarEvolution/trip-count.ll
Sanjoy Das 7ac8ad9906 Be wary of abnormal exits from loop when exploiting UB
We can safely rely on a NoWrap add recurrence causing UB down the road
only if we know the loop does not have a exit expressed in a way that is
opaque to ScalarEvolution (e.g. by a function call that conditionally
calls exit(0)).

I believe with this change PR28012 is fixed.

Note: I had to change some llvm-lit tests in LoopReroll, since it looks
like they were depending on this incorrect behavior.

llvm-svn: 272237
2016-06-09 01:13:59 +00:00

114 lines
3.8 KiB
LLVM

; RUN: opt < %s -analyze -scalar-evolution -scalar-evolution-max-iterations=0 | FileCheck %s
; RUN: opt < %s -passes='print<scalar-evolution>' -disable-output 2>&1 | FileCheck %s
; PR1101
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@A = weak global [1000 x i32] zeroinitializer, align 32
; CHECK-LABEL: Determining loop execution counts for: @test1
; CHECK: backedge-taken count is 10000
define void @test1(i32 %N) {
entry:
br label %bb3
bb: ; preds = %bb3
%tmp = getelementptr [1000 x i32], [1000 x i32]* @A, i32 0, i32 %i.0 ; <i32*> [#uses=1]
store i32 123, i32* %tmp
%tmp2 = add i32 %i.0, 1 ; <i32> [#uses=1]
br label %bb3
bb3: ; preds = %bb, %entry
%i.0 = phi i32 [ 0, %entry ], [ %tmp2, %bb ] ; <i32> [#uses=3]
%tmp3 = icmp sle i32 %i.0, 9999 ; <i1> [#uses=1]
br i1 %tmp3, label %bb, label %bb5
bb5: ; preds = %bb3
br label %return
return: ; preds = %bb5
ret void
}
; PR22795
; CHECK-LABEL: Classifying expressions for: @test2
; CHECK: %iv = phi i32 [ -1, %entry ], [ %next.1, %for.inc.1 ]
; CHECK-NEXT: --> {-1,+,2}<%preheader> U: full-set S: full-set Exits: 13
define i32 @test2() {
entry:
%bins = alloca [16 x i64], align 16
%0 = bitcast [16 x i64]* %bins to i8*
call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 128, i32 16, i1 false)
br label %preheader
preheader: ; preds = %for.inc.1, %entry
%v11 = phi i64 [ 0, %entry ], [ %next12.1, %for.inc.1 ]
%iv = phi i32 [ -1, %entry ], [ %next.1, %for.inc.1 ]
%cmp = icmp sgt i64 %v11, 0
br i1 %cmp, label %for.body, label %for.inc
for.body: ; preds = %preheader
%zext = zext i32 %iv to i64
%arrayidx = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 %v11
%loaded = load i64, i64* %arrayidx, align 8
%add = add i64 %loaded, 1
%add2 = add i64 %add, %zext
store i64 %add2, i64* %arrayidx, align 8
br label %for.inc
for.inc: ; preds = %for.body, %preheader
%next12 = add nuw nsw i64 %v11, 1
%next = add nsw i32 %iv, 1
br i1 true, label %for.body.1, label %for.inc.1
end: ; preds = %for.inc.1
%arrayidx8 = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 2
%load = load i64, i64* %arrayidx8, align 16
%shr4 = lshr i64 %load, 32
%conv = trunc i64 %shr4 to i32
ret i32 %conv
for.body.1: ; preds = %for.inc
%zext.1 = zext i32 %next to i64
%arrayidx.1 = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 %next12
%loaded.1 = load i64, i64* %arrayidx.1, align 8
%add.1 = add i64 %loaded.1, 1
%add2.1 = add i64 %add.1, %zext.1
store i64 %add2.1, i64* %arrayidx.1, align 8
br label %for.inc.1
for.inc.1: ; preds = %for.body.1, %for.inc
%next12.1 = add nuw nsw i64 %next12, 1
%next.1 = add nuw nsw i32 %next, 1
%exitcond.1 = icmp eq i64 %next12.1, 16
br i1 %exitcond.1, label %end, label %preheader
}
; Function Attrs: nounwind
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) #0
declare void @may_exit() nounwind
define void @pr28012(i32 %n) {
; CHECK-LABEL: Classifying expressions for: @pr28012
; CHECK: Loop %loop: backedge-taken count is -1431655751
; CHECK: Loop %loop: max backedge-taken count is -1431655751
; CHECK: Loop %loop: Predicated backedge-taken count is -1431655751
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
%iv.inc = add nsw i32 %iv, 3
call void @may_exit()
%becond = icmp ne i32 %iv.inc, 46
br i1 %becond, label %loop, label %leave
leave:
ret void
}