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[BasicAA] Revert r218714 - Make better use of zext and sign information.

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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
This commit is contained in:
Lang Hames 2014-10-03 01:33:47 +00:00
parent e04fe8733a
commit 21702da64c
3 changed files with 2 additions and 95 deletions
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31
lib/Analysis/BasicAliasAnalysis.cpp
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@ -254,10 +254,7 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
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 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
// 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 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
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

1
test/Analysis/BasicAA/phi-aa.ll
View File

@ -39,7 +39,6 @@ return:
; CHECK-LABEL: pr18068
; CHECK: MayAlias: i32* %0, i32* %arrayidx5
; CHECK: NoAlias: i32* %arrayidx13, i32* %arrayidx5
define i32 @pr18068(i32* %jj7, i32* %j) {
entry:

65
test/Analysis/BasicAA/zext.ll
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@ -1,65 +0,0 @@
; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; CHECK-LABEL: test_with_zext
; CHECK: NoAlias: i8* %a, i8* %b
define void @test_with_zext() {
%1 = tail call i8* @malloc(i64 120)
%a = getelementptr inbounds i8* %1, i64 8
%2 = getelementptr inbounds i8* %1, i64 16
%3 = zext i32 3 to i64
%b = getelementptr inbounds i8* %2, i64 %3
ret void
}
; CHECK-LABEL: test_with_lshr
; CHECK: NoAlias: i8* %a, i8* %b
define void @test_with_lshr(i64 %i) {
%1 = tail call i8* @malloc(i64 120)
%a = getelementptr inbounds i8* %1, i64 8
%2 = getelementptr inbounds i8* %1, i64 16
%3 = lshr i64 %i, 2
%b = getelementptr inbounds i8* %2, i64 %3
ret void
}
; CHECK-LABEL: test_with_a_loop
; CHECK: NoAlias: i8* %a, i8* %b
define void @test_with_a_loop() {
%1 = tail call i8* @malloc(i64 120)
%a = getelementptr inbounds i8* %1, i64 8
%2 = getelementptr inbounds i8* %1, i64 16
br label %for.loop
for.loop:
%i = phi i32 [ 0, %0 ], [ %i.next, %for.loop ]
%3 = zext i32 %i to i64
%b = getelementptr inbounds i8* %2, i64 %3
%i.next = add nuw nsw i32 %i, 1
%4 = icmp eq i32 %i.next, 10
br i1 %4, label %for.loop.exit, label %for.loop
for.loop.exit:
ret void
}
; CHECK-LABEL: test_sign_extension
; CHECK: PartialAlias: i64* %b.i64, i8* %a
define void @test_sign_extension(i32 %p) {
%1 = tail call i8* @malloc(i64 120)
%p.64 = zext i32 %p to i64
%a = getelementptr inbounds i8* %1, i64 %p.64
%p.minus1 = add i32 %p, -1
%p.minus1.64 = zext i32 %p.minus1 to i64
%b.i8 = getelementptr inbounds i8* %1, i64 %p.minus1.64
%b.i64 = bitcast i8* %b.i8 to i64*
ret void
}
; Function Attrs: nounwind
declare noalias i8* @malloc(i64)