diff options
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 17 | ||||
| -rw-r--r-- | test/Analysis/ScalarEvolution/nsw.ll | 4 |
2 files changed, 16 insertions, 5 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index c2f3ac0..aab95ae 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -2785,10 +2785,21 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { HasNSW = true; } else if (const GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) { - // If the increment is a GEP, then we know it won't perform an - // unsigned overflow, because the address space cannot be + // If the increment is a GEP, then we know it won't perform a + // signed overflow, because the address space cannot be // wrapped around. - HasNUW |= GEP->isInBounds(); + // + // NOTE: This isn't strictly true, because you could have an + // object straddling the 2G address boundary in a 32-bit address + // space (for example). We really want to model this as a "has + // no signed/unsigned wrap" where the base pointer is treated as + // unsigned and the increment is known to not have signed + // wrapping. + // + // This is a highly theoretical concern though, and this is good + // enough for all cases we know of at this point. :) + // + HasNSW |= GEP->isInBounds(); } const SCEV *StartVal = getSCEV(StartValueV); diff --git a/test/Analysis/ScalarEvolution/nsw.ll b/test/Analysis/ScalarEvolution/nsw.ll index 530ed39..010cf60 100644 --- a/test/Analysis/ScalarEvolution/nsw.ll +++ b/test/Analysis/ScalarEvolution/nsw.ll @@ -62,11 +62,11 @@ for.body.lr.ph.i.i: ; preds = %entry for.body.i.i: ; preds = %for.body.i.i, %for.body.lr.ph.i.i %__first.addr.02.i.i = phi i32* [ %begin, %for.body.lr.ph.i.i ], [ %ptrincdec.i.i, %for.body.i.i ] ; CHECK: %__first.addr.02.i.i -; CHECK-NEXT: --> {%begin,+,4}<nuw><%for.body.i.i> +; CHECK-NEXT: --> {%begin,+,4}<nsw><%for.body.i.i> store i32 0, i32* %__first.addr.02.i.i, align 4 %ptrincdec.i.i = getelementptr inbounds i32* %__first.addr.02.i.i, i64 1 ; CHECK: %ptrincdec.i.i -; CHECK-NEXT: --> {(4 + %begin),+,4}<nuw><%for.body.i.i> +; CHECK-NEXT: --> {(4 + %begin),+,4}<nsw><%for.body.i.i> %cmp.i.i = icmp eq i32* %ptrincdec.i.i, %end br i1 %cmp.i.i, label %for.cond.for.end_crit_edge.i.i, label %for.body.i.i |