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llvm-project/llvm/test/Analysis/ScalarEvolution/pr24757.ll

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[ScalarEvolution] Fix PR24757. Summary: PR24757 was caused by some incorect math in `ScalarEvolution::HowFarToZero` -- the smallest unsigned solution for X in 2^N * A = 2^N * X is not necessarily A. Reviewers: atrick, majnemer, meheff Subscribers: llvm-commits, sanjoy Differential Revision: http://reviews.llvm.org/D12721 llvm-svn: 247242
2015-09-10 13:27:38 +08:00
; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
[SCEV] Make getUDivExactExpr handle non-nuw multiplies correctly. To avoid regressions, make ScalarEvolution::createSCEV a bit more clever. Also get rid of some useless code in ScalarEvolution::howFarToZero which was hiding this bug. No new testcase because it's impossible to actually expose this bug: we don't have any in-tree users of getUDivExactExpr besides the two functions I just mentioned, and they both dodged the problem. I'll try to add some interesting users in a followup. Differential Revision: https://reviews.llvm.org/D28587 llvm-svn: 292449
2017-01-19 07:56:42 +08:00
; CHECK: Loop %bb1: backedge-taken count is ((2 * %a.promoted) /u 2)
[ScalarEvolution] Fix PR24757. Summary: PR24757 was caused by some incorect math in `ScalarEvolution::HowFarToZero` -- the smallest unsigned solution for X in 2^N * A = 2^N * X is not necessarily A. Reviewers: atrick, majnemer, meheff Subscribers: llvm-commits, sanjoy Differential Revision: http://reviews.llvm.org/D12721 llvm-svn: 247242
2015-09-10 13:27:38 +08:00
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.10.0"
@a = global i8 -127, align 1
@b = common global i32 0, align 4
declare void @use(i32)
define i32 @main() {
bb:
%a.promoted = load i8, i8* @a
br label %bb1
bb1: ; preds = %bb1, %bb
%tmp = phi i8 [ %tmp2, %bb1 ], [ %a.promoted, %bb ]
%tmp2 = add i8 %tmp, -1
%tmp3 = sext i8 %tmp to i32
%tmp4 = xor i32 %tmp3, -1
%tmp5 = sext i8 %tmp2 to i32
%tmpf = sub nsw i32 %tmp4, %tmp5
%tmp6 = trunc i32 %tmpf to i8
%tmp7 = icmp eq i8 %tmp6, 0
br i1 %tmp7, label %bb8, label %bb1
bb8: ; preds = %bb1
store i8 %tmp2, i8* @a
store i32 %tmp4, i32* @b
%tmp9 = sext i8 %tmp2 to i32
call void @use(i32 %tmp9)
ret i32 0
}