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When checking for signed multiplication overflow, watch out for INT_MIN and -1.

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This fixes PR9845.

llvm-svn: 131919
This commit is contained in:
Dan Gohman 2011-05-23 21:07:39 +00:00
parent 76f8f3d479
commit e6a4a2aa6f
2 changed files with 20 additions and 0 deletions
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2
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -2522,6 +2522,8 @@ void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
// Check that multiplying with the unfolded offset doesn't overflow.
if (F.UnfoldedOffset != 0) {
if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
continue;
F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
continue;

18
test/CodeGen/X86/lsr-overflow.ll
View File

@ -25,3 +25,21 @@ __ABContainsLabel.exit:
%cmp = icmp eq i64 %indvar, 9223372036854775807
ret i1 %cmp
}
define void @func_37() noreturn nounwind readonly {
entry:
br label %for.body
for.body: ; preds = %for.inc8, %entry
%indvar = phi i64 [ 0, %entry ], [ %indvar.next, %for.inc8 ]
%sub.i = add i64 undef, %indvar
%cmp.i = icmp eq i64 %sub.i, -9223372036854775808
br i1 undef, label %for.inc8, label %for.cond4
for.cond4: ; preds = %for.cond4, %for.body
br label %for.cond4
for.inc8: ; preds = %for.body
%indvar.next = add i64 %indvar, 1
br label %for.body
}