[BasicAA] Revert r218714 - Make better use of zext and sign information.
This patch broke 447.dealII on Darwin. I'm currently working on a reduced
test-case, but reverting for now to keep the bots happy.
<rdar://problem/18530107>
llvm-svn: 218944
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index f4052b9..9cfd02c 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -254,10 +254,7 @@
Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension,
DL, Depth+1, AT, DT);
Scale = Scale.zext(OldWidth);
-
- // We have to sign-extend even if Extension == EK_ZeroExt as we can't
- // decompose a sign extension (i.e. zext(x - 1) != zext(x) - zext(-1)).
- Offset = Offset.sext(OldWidth);
+ Offset = Offset.zext(OldWidth);
return Result;
}
@@ -1058,26 +1055,8 @@
// Grab the least significant bit set in any of the scales.
if (!GEP1VariableIndices.empty()) {
uint64_t Modulo = 0;
- bool AllPositive = true;
- for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i) {
- const Value *V = GEP1VariableIndices[i].V;
+ for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i)
Modulo |= (uint64_t)GEP1VariableIndices[i].Scale;
-
- // If the variable's been zero-extended or begins with a zero then
- // we know it's positive. regardless of whether the value is signed
- // or unsigned.
- bool SignKnownZero, SignKnownOne;
- ComputeSignBit(
- const_cast<Value *>(V),
- SignKnownZero, SignKnownOne,
- DL, 0, AT, nullptr, DT);
- bool IsZExt = GEP1VariableIndices[i].Extension == EK_ZeroExt;
- AllPositive &= IsZExt || SignKnownZero;
-
- // If the Value is currently positive but could change in a cycle,
- // then we can't guarantee it'll always br positive.
- AllPositive &= isValueEqualInPotentialCycles(V, V);
- }
Modulo = Modulo ^ (Modulo & (Modulo - 1));
// We can compute the difference between the two addresses
@@ -1087,12 +1066,6 @@
if (V1Size != UnknownSize && V2Size != UnknownSize &&
ModOffset >= V2Size && V1Size <= Modulo - ModOffset)
return NoAlias;
-
- // If we know all the variables are positive, then GEP1 >= GEP1BasePtr.
- // If GEP1BasePtr > V2 (GEP1BaseOffset > 0) then we know the pointers
- // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
- if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t) GEP1BaseOffset)
- return NoAlias;
}
// Statically, we can see that the base objects are the same, but the