summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat
-rw-r--r--llvm/lib/Analysis/BasicAliasAnalysis.cpp60
-rw-r--r--llvm/test/Analysis/BasicAA/phi-aa.ll1
-rw-r--r--llvm/test/Analysis/BasicAA/zext.ll209
3 files changed, 265 insertions, 5 deletions
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 11b33326fb7..9a7d312c65c 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -207,6 +207,14 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
return V;
}
+ if (ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
+ // if it's a constant, just convert it to an offset
+ // and remove the variable.
+ Offset += Const->getValue();
+ assert(Scale == 0 && "Constant values don't have a scale");
+ return V;
+ }
+
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
switch (BOp->getOpcode()) {
@@ -254,7 +262,10 @@ 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);
- Offset = Offset.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);
return Result;
}
@@ -1051,12 +1062,45 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
}
}
- // Try to distinguish something like &A[i][1] against &A[42][0].
- // Grab the least significant bit set in any of the scales.
if (!GEP1VariableIndices.empty()) {
uint64_t Modulo = 0;
- for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i)
- Modulo |= (uint64_t)GEP1VariableIndices[i].Scale;
+ bool AllPositive = true;
+ for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i) {
+
+ // Try to distinguish something like &A[i][1] against &A[42][0].
+ // Grab the least significant bit set in any of the scales. We
+ // don't need std::abs here (even if the scale's negative) as we'll
+ // be ^'ing Modulo with itself later.
+ Modulo |= (uint64_t) GEP1VariableIndices[i].Scale;
+
+ if (AllPositive) {
+ // If the Value could change between cycles, then any reasoning about
+ // the Value this cycle may not hold in the next cycle. We'll just
+ // give up if we can't determine conditions that hold for every cycle:
+ const Value *V = GEP1VariableIndices[i].V;
+
+ bool SignKnownZero, SignKnownOne;
+ ComputeSignBit(
+ const_cast<Value *>(V),
+ SignKnownZero, SignKnownOne,
+ DL, 0, AT, nullptr, DT);
+
+ // Zero-extension widens the variable, and so forces the sign
+ // bit to zero.
+ bool IsZExt = GEP1VariableIndices[i].Extension == EK_ZeroExt;
+ SignKnownZero |= IsZExt;
+ SignKnownOne &= !IsZExt;
+
+ // If the variable begins with a zero then we know it's
+ // positive, regardless of whether the value is signed or
+ // unsigned.
+ int64_t Scale = GEP1VariableIndices[i].Scale;
+ AllPositive =
+ (SignKnownZero && Scale >= 0) ||
+ (SignKnownOne && Scale < 0);
+ }
+ }
+
Modulo = Modulo ^ (Modulo & (Modulo - 1));
// We can compute the difference between the two addresses
@@ -1066,6 +1110,12 @@ 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
diff --git a/llvm/test/Analysis/BasicAA/phi-aa.ll b/llvm/test/Analysis/BasicAA/phi-aa.ll
index 74279e1c4c9..c1100f1d36f 100644
--- a/llvm/test/Analysis/BasicAA/phi-aa.ll
+++ b/llvm/test/Analysis/BasicAA/phi-aa.ll
@@ -39,6 +39,7 @@ return:
; CHECK-LABEL: pr18068
; CHECK: MayAlias: i32* %0, i32* %arrayidx5
+; CHECK: NoAlias: i32* %arrayidx13, i32* %arrayidx5
define i32 @pr18068(i32* %jj7, i32* %j) {
entry:
diff --git a/llvm/test/Analysis/BasicAA/zext.ll b/llvm/test/Analysis/BasicAA/zext.ll
new file mode 100644
index 00000000000..b59d16cc5f5
--- /dev/null
+++ b/llvm/test/Analysis/BasicAA/zext.ll
@@ -0,0 +1,209 @@
+; 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(i8* %mem) {
+ br label %for.loop
+
+for.loop:
+ %i = phi i32 [ 0, %0 ], [ %i.plus1, %for.loop ]
+ %a = getelementptr inbounds i8* %mem, i64 8
+ %a.plus1 = getelementptr inbounds i8* %mem, i64 16
+ %i.64 = zext i32 %i to i64
+ %b = getelementptr inbounds i8* %a.plus1, i64 %i.64
+ %i.plus1 = add nuw nsw i32 %i, 1
+ %cmp = icmp eq i32 %i.plus1, 10
+ br i1 %cmp, label %for.loop.exit, label %for.loop
+
+for.loop.exit:
+ ret void
+}
+
+; CHECK-LABEL: test_with_varying_base_pointer_in_loop
+; CHECK: NoAlias: i8* %a, i8* %b
+
+define void @test_with_varying_base_pointer_in_loop(i8* %mem.orig) {
+ br label %for.loop
+
+for.loop:
+ %mem = phi i8* [ %mem.orig, %0 ], [ %mem.plus1, %for.loop ]
+ %i = phi i32 [ 0, %0 ], [ %i.plus1, %for.loop ]
+ %a = getelementptr inbounds i8* %mem, i64 8
+ %a.plus1 = getelementptr inbounds i8* %mem, i64 16
+ %i.64 = zext i32 %i to i64
+ %b = getelementptr inbounds i8* %a.plus1, i64 %i.64
+ %i.plus1 = add nuw nsw i32 %i, 1
+ %mem.plus1 = getelementptr inbounds i8* %mem, i64 8
+ %cmp = icmp eq i32 %i.plus1, 10
+ br i1 %cmp, 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
+}
+
+; CHECK-LABEL: test_fe_tools
+; CHECK: PartialAlias: i32* %a, i32* %b
+
+define void @test_fe_tools([8 x i32]* %values) {
+ br label %reorder
+
+for.loop:
+ %i = phi i32 [ 0, %reorder ], [ %i.next, %for.loop ]
+ %idxprom = zext i32 %i to i64
+ %b = getelementptr inbounds [8 x i32]* %values, i64 0, i64 %idxprom
+ %i.next = add nuw nsw i32 %i, 1
+ %1 = icmp eq i32 %i.next, 10
+ br i1 %1, label %for.loop.exit, label %for.loop
+
+reorder:
+ %a = getelementptr inbounds [8 x i32]* %values, i64 0, i64 1
+ br label %for.loop
+
+for.loop.exit:
+ ret void
+}
+
+@b = global i32 0, align 4
+@d = global i32 0, align 4
+
+; CHECK-LABEL: test_spec2006
+; CHECK: PartialAlias: i32** %x, i32** %y
+
+define void @test_spec2006() {
+ %h = alloca [1 x [2 x i32*]], align 16
+ %d.val = load i32* @d, align 4
+ %d.promoted = sext i32 %d.val to i64
+ %1 = icmp slt i32 %d.val, 2
+ br i1 %1, label %.lr.ph, label %3
+
+.lr.ph: ; preds = %0
+ br label %2
+
+; <label>:2 ; preds = %.lr.ph, %2
+ %i = phi i32 [ %d.val, %.lr.ph ], [ %i.plus1, %2 ]
+ %i.promoted = sext i32 %i to i64
+ %x = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 %d.promoted, i64 %i.promoted
+ %i.plus1 = add nsw i32 %i, 1
+ %cmp = icmp slt i32 %i.plus1, 2
+ br i1 %cmp, label %2, label %3
+
+; <label>:3 ; preds = %._crit_edge, %0
+ %y = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 0, i64 1
+ ret void
+}
+
+; CHECK-LABEL: test_modulo_analysis_easy_case
+; CHECK: NoAlias: i32** %x, i32** %y
+
+define void @test_modulo_analysis_easy_case(i64 %i) {
+ %h = alloca [1 x [2 x i32*]], align 16
+ %x = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 %i, i64 0
+ %y = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 0, i64 1
+ ret void
+}
+
+; CHECK-LABEL: test_modulo_analysis_in_loop
+; CHECK: NoAlias: i32** %x, i32** %y
+
+define void @test_modulo_analysis_in_loop() {
+ %h = alloca [1 x [2 x i32*]], align 16
+ br label %for.loop
+
+for.loop:
+ %i = phi i32 [ 0, %0 ], [ %i.plus1, %for.loop ]
+ %i.promoted = sext i32 %i to i64
+ %x = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 %i.promoted, i64 0
+ %y = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 0, i64 1
+ %i.plus1 = add nsw i32 %i, 1
+ %cmp = icmp slt i32 %i.plus1, 2
+ br i1 %cmp, label %for.loop, label %for.loop.exit
+
+for.loop.exit:
+ ret void
+}
+
+; CHECK-LABEL: test_modulo_analysis_with_global
+; CHECK: PartialAlias: i32** %x, i32** %y
+
+define void @test_modulo_analysis_with_global() {
+ %h = alloca [1 x [2 x i32*]], align 16
+ %b = load i32* @b, align 4
+ %b.promoted = sext i32 %b to i64
+ br label %for.loop
+
+for.loop:
+ %i = phi i32 [ 0, %0 ], [ %i.plus1, %for.loop ]
+ %i.promoted = sext i32 %i to i64
+ %x = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 %i.promoted, i64 %b.promoted
+ %y = getelementptr inbounds [1 x [2 x i32*]]* %h, i64 0, i64 0, i64 1
+ %i.plus1 = add nsw i32 %i, 1
+ %cmp = icmp slt i32 %i.plus1, 2
+ br i1 %cmp, label %for.loop, label %for.loop.exit
+
+for.loop.exit:
+ ret void
+}
+
+; CHECK-LABEL: test_const_eval
+; CHECK: NoAlias: i8* %a, i8* %b
+define void @test_const_eval(i8* %ptr, i64 %offset) {
+ %a = getelementptr inbounds i8* %ptr, i64 %offset
+ %a.dup = getelementptr inbounds i8* %ptr, i64 %offset
+ %three = zext i32 3 to i64
+ %b = getelementptr inbounds i8* %a.dup, i64 %three
+ ret void
+}
+
+; CHECK-LABEL: test_const_eval_scaled
+; CHECK: MustAlias: i8* %a, i8* %b
+define void @test_const_eval_scaled(i8* %ptr) {
+ %three = zext i32 3 to i64
+ %six = mul i64 %three, 2
+ %a = getelementptr inbounds i8* %ptr, i64 %six
+ %b = getelementptr inbounds i8* %ptr, i64 6
+ ret void
+}
+
+; Function Attrs: nounwind
+declare noalias i8* @malloc(i64)
OpenPOWER on IntegriCloud