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[AlignmentFromAssumptions] Don't divide by zero for unknown starting alignment

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The routine that determines an alignment given some SCEV returns zero if the
answer is unknown. In a case where we could determine the increment of an
AddRec but not the starting alignment, we would compute the integer modulus by
zero (which is illegal and traps). Prevent this by returning early if either
the start or increment alignment is unknown (zero).

llvm-svn: 217544
This commit is contained in:
Hal Finkel 2014-09-10 21:05:52 +00:00
parent 20fb2f8367
commit 22791b474e
2 changed files with 158 additions and 2 deletions
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6
lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
View File

@ -179,7 +179,9 @@ static unsigned getNewAlignment(const SCEV *AASCEV, const SCEV *AlignSCEV,
DEBUG(dbgs() << "\tnew start alignment: " << NewAlignment << "\n");
DEBUG(dbgs() << "\tnew inc alignment: " << NewIncAlignment << "\n");
if (NewAlignment > NewIncAlignment) {
if (!NewAlignment || !NewIncAlignment) {
return 0;
} else if (NewAlignment > NewIncAlignment) {
if (NewAlignment % NewIncAlignment == 0) {
DEBUG(dbgs() << "\tnew start/inc alignment: " <<
NewIncAlignment << "\n");
@ -191,7 +193,7 @@ static unsigned getNewAlignment(const SCEV *AASCEV, const SCEV *AlignSCEV,
NewAlignment << "\n");
return NewAlignment;
}
} else if (NewIncAlignment == NewAlignment && NewIncAlignment) {
} else if (NewIncAlignment == NewAlignment) {
DEBUG(dbgs() << "\tnew start/inc alignment: " <<
NewAlignment << "\n");
return NewAlignment;

154
test/Transforms/AlignmentFromAssumptions/start-unk.ll Normal file
View File

@ -0,0 +1,154 @@
; RUN: opt -alignment-from-assumptions -S < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%type1 = type { %type2 }
%type2 = type { [4 x i8] }
; Function Attrs: nounwind
declare void @llvm.assume(i1) #0
; Function Attrs: nounwind readnone
declare i32 @llvm.bswap.i32(i32) #1
; Function Attrs: nounwind uwtable
define void @test1() unnamed_addr #2 align 2 {
; CHECK-LABEL: @test1
entry:
br i1 undef, label %if.then, label %if.end
if.then: ; preds = %entry
unreachable
if.end: ; preds = %entry
br i1 undef, label %return, label %if.end8
if.end8: ; preds = %if.end
br i1 undef, label %if.then13, label %if.end14
if.then13: ; preds = %if.end8
unreachable
if.end14: ; preds = %if.end8
br i1 undef, label %cond.false.i129, label %cond.end.i136
cond.false.i129: ; preds = %if.end14
unreachable
cond.end.i136: ; preds = %if.end14
br i1 undef, label %land.lhs.true.i, label %if.end.i145
land.lhs.true.i: ; preds = %cond.end.i136
br i1 undef, label %if.end.i145, label %if.then.i137
if.then.i137: ; preds = %land.lhs.true.i
br i1 undef, label %cond.false8.i, label %cond.end9.i
cond.false8.i: ; preds = %if.then.i137
unreachable
cond.end9.i: ; preds = %if.then.i137
br i1 undef, label %if.then23, label %if.end24
if.end.i145: ; preds = %land.lhs.true.i, %cond.end.i136
unreachable
if.then23: ; preds = %cond.end9.i
unreachable
if.end24: ; preds = %cond.end9.i
br i1 undef, label %for.end, label %for.body.lr.ph
for.body.lr.ph: ; preds = %if.end24
unreachable
for.end: ; preds = %if.end24
br i1 undef, label %if.end123, label %if.then121
if.then121: ; preds = %for.end
unreachable
if.end123: ; preds = %for.end
br i1 undef, label %if.end150, label %if.then126
if.then126: ; preds = %if.end123
%ptrint.i.i185 = ptrtoint %type1* undef to i64
%maskedptr.i.i186 = and i64 %ptrint.i.i185, 1
%maskcond.i.i187 = icmp eq i64 %maskedptr.i.i186, 0
tail call void @llvm.assume(i1 %maskcond.i.i187) #0
%ret.0..sroa_cast.i.i188 = bitcast %type1* undef to i32*
%ret.0.copyload.i.i189 = load i32* %ret.0..sroa_cast.i.i188, align 2
; CHECK: load {{.*}} align 2
%0 = tail call i32 @llvm.bswap.i32(i32 %ret.0.copyload.i.i189) #0
%conv131 = zext i32 %0 to i64
%add.ptr132 = getelementptr inbounds i8* undef, i64 %conv131
%1 = bitcast i8* %add.ptr132 to %type1*
br i1 undef, label %if.end150, label %if.end.i173
if.end.i173: ; preds = %if.then126
br i1 undef, label %test1.exit, label %cond.false.i.i.i.i174
cond.false.i.i.i.i174: ; preds = %if.end.i173
unreachable
test1.exit: ; preds = %if.end.i173
br i1 undef, label %test1a.exit, label %if.end.i124
if.end.i124: ; preds = %test1.exit
unreachable
test1a.exit: ; preds = %test1.exit
br i1 undef, label %if.end150, label %for.body137.lr.ph
for.body137.lr.ph: ; preds = %test1a.exit
br label %for.body137
for.body137: ; preds = %test1b.exit, %for.body137.lr.ph
%ShndxTable.0309 = phi %type1* [ %1, %for.body137.lr.ph ], [ %incdec.ptr, %test1b.exit ]
%ret.0..sroa_cast.i.i106 = bitcast %type1* %ShndxTable.0309 to i32*
br i1 undef, label %for.body137.if.end146_crit_edge, label %if.then140
for.body137.if.end146_crit_edge: ; preds = %for.body137
%incdec.ptr = getelementptr inbounds %type1* %ShndxTable.0309, i64 1
br i1 undef, label %cond.false.i70, label %cond.end.i
if.then140: ; preds = %for.body137
%ret.0.copyload.i.i102 = load i32* %ret.0..sroa_cast.i.i106, align 2
; CHECK: load {{.*}} align 2
unreachable
cond.false.i70: ; preds = %for.body137.if.end146_crit_edge
unreachable
cond.end.i: ; preds = %for.body137.if.end146_crit_edge
br i1 undef, label %test1b.exit, label %cond.false.i.i
cond.false.i.i: ; preds = %cond.end.i
unreachable
test1b.exit: ; preds = %cond.end.i
br i1 undef, label %if.end150, label %for.body137
if.end150: ; preds = %test1b.exit, %test1a.exit, %if.then126, %if.end123
br i1 undef, label %for.end176, label %for.body155.lr.ph
for.body155.lr.ph: ; preds = %if.end150
unreachable
for.end176: ; preds = %if.end150
unreachable
return: ; preds = %if.end
ret void
}
attributes #0 = { nounwind }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind uwtable }