[llvm] r271415 - Claim NoAlias if two GEPs index different fields of the same struct
Daniel Berlin via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 1 11:12:01 PDT 2016
Author: dannyb
Date: Wed Jun 1 13:12:01 2016
New Revision: 271415
URL: http://llvm.org/viewvc/llvm-project?rev=271415&view=rev
Log:
Claim NoAlias if two GEPs index different fields of the same struct
Patch by Taewook Oh
Summary: Patch for Bug 27478. Make BasicAliasAnalysis claims NoAlias if two GEPs index different fields of the same structure.
Reviewers: hfinkel, dberlin
Subscribers: dberlin, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D20665
Added:
llvm/trunk/test/Analysis/BasicAA/noalias-structure.ll
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=271415&r1=271414&r2=271415&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Wed Jun 1 13:12:01 2016
@@ -834,8 +834,42 @@ static AliasResult aliasSameBasePointerG
// Try to determine whether GEP1 and GEP2 index through arrays, into structs,
// such that the struct field accesses provably cannot alias.
// We also need at least two indices (the pointer, and the struct field).
- if (GEP1->getNumIndices() != GEP2->getNumIndices() ||
- GEP1->getNumIndices() < 2)
+ if (GEP1->getNumIndices() < 2)
+ return MayAlias;
+
+ // If both GEP1 and GEP2 have the inbounds keyword but index different fields
+ // of the same struct, they do not alias.
+ if (GEP1->isInBounds() && GEP2->isInBounds()) {
+ auto Opi1 = GEP1->op_begin() + 1;
+ auto Opi2 = GEP2->op_begin() + 1;
+ auto Ope1 = GEP1->op_end();
+ auto Ope2 = GEP2->op_end();
+
+ SmallVector<Value *, 8> IntermediateIndices;
+ ConstantInt *C1 = nullptr;
+ ConstantInt *C2 = nullptr;
+ while (Opi1 != Ope1 && Opi2 != Ope2 &&
+ (C1 = dyn_cast<ConstantInt>(*Opi1)) &&
+ (C2 = dyn_cast<ConstantInt>(*Opi2))) {
+ if (C1 == C2) {
+ IntermediateIndices.push_back(C1);
+ ++Opi1;
+ ++Opi2;
+ } else {
+ // Both GEPs share the same pointer operand and access through the same
+ // indices up to this point, but now they are having different index
+ // values. At this point, if the indexed type is a StructType, this means
+ // that two GEPs are for two different fields in the same structure.
+ auto *Ty = GetElementPtrInst::getIndexedType(
+ GEP1->getSourceElementType(), IntermediateIndices);
+ if (isa<StructType>(Ty))
+ return NoAlias;
+ break;
+ }
+ }
+ }
+
+ if (GEP1->getNumIndices() != GEP2->getNumIndices())
return MayAlias;
// If we don't know the size of the accesses through both GEPs, we can't
Added: llvm/trunk/test/Analysis/BasicAA/noalias-structure.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/noalias-structure.ll?rev=271415&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/BasicAA/noalias-structure.ll (added)
+++ llvm/trunk/test/Analysis/BasicAA/noalias-structure.ll Wed Jun 1 13:12:01 2016
@@ -0,0 +1,36 @@
+; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.Type = type { [10 x i32], i32 }
+ at Foo = external global %struct.Type, align 4
+
+; /// Check that BasicAA claims no alias between different fileds of a structure
+; void test() {
+; for (unsigned i = 0 ; i < 10 ; i++)
+; Foo.arr[i] += Foo.i;
+; }
+
+define void @test() {
+; CHECK-LABEL: Function: test:
+entry:
+ %0 = load i32, i32* getelementptr inbounds (%struct.Type, %struct.Type* @Foo, i64 0, i32 1), align 4
+ br label %for.body
+
+for.cond.cleanup: ; preds = %for.body
+ ret void
+
+for.body: ; preds = %for.body, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+
+ %arrayidx = getelementptr inbounds %struct.Type, %struct.Type* @Foo, i64 0, i32 0, i64 %indvars.iv
+ %1 = load i32, i32* %arrayidx, align 4
+ %add = add nsw i32 %1, %0
+ store i32 %add, i32* %arrayidx, align 4
+; CHECK: NoAlias: i32* %arrayidx, i32* getelementptr inbounds (%struct.Type, %struct.Type* @Foo, i64 0, i32 1)
+
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp eq i64 %indvars.iv.next, 10
+ br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}
Modified: llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll?rev=271415&r1=271414&r2=271415&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll Wed Jun 1 13:12:01 2016
@@ -765,22 +765,18 @@ for.end:
ret i32 %7
}
-
-;; === Now, the tests that we could vectorize with induction changes or run-time checks ===
-
-
-; /// Different objects, swapped induction, alias at the end
-; int mayAlias01 (int a) {
+; /// Different objects, swapped induction
+; int noAlias15(int a) {
; int i;
; for (i=0; i<SIZE; i++)
; Foo.A[i] = Foo.B[SIZE-i-1] + a;
; return Foo.A[a];
; }
-; CHECK-LABEL: define i32 @mayAlias01(
-; CHECK-NOT: add nsw <4 x i32>
+; CHECK-LABEL: define i32 @noAlias15(
+; CHECK: add nsw <4 x i32>
; CHECK: ret
-define i32 @mayAlias01(i32 %a) nounwind {
+define i32 @noAlias15(i32 %a) nounwind {
entry:
%a.addr = alloca i32, align 4
%i = alloca i32, align 4
@@ -819,18 +815,18 @@ for.end:
ret i32 %7
}
-; /// Different objects, swapped induction, alias at the beginning
-; int mayAlias02 (int a) {
+; /// Different objects, swapped induction
+; int noAlias16 (int a) {
; int i;
; for (i=0; i<SIZE; i++)
; Foo.A[SIZE-i-1] = Foo.B[i] + a;
; return Foo.A[a];
; }
-; CHECK-LABEL: define i32 @mayAlias02(
-; CHECK-NOT: add nsw <4 x i32>
+; CHECK-LABEL: define i32 @noAlias16(
+; CHECK: add nsw <4 x i32>
; CHECK: ret
-define i32 @mayAlias02(i32 %a) nounwind {
+define i32 @noAlias16(i32 %a) nounwind {
entry:
%a.addr = alloca i32, align 4
%i = alloca i32, align 4
@@ -869,75 +865,21 @@ for.end:
ret i32 %7
}
-; /// Pointer access, run-time check added
-; int mayAlias03 (int a) {
-; int i;
-; for (i=0; i<SIZE; i++)
-; *(PA+i) = *(PB+SIZE-i-1) + a;
-; return *(PA+a);
-; }
-; CHECK-LABEL: define i32 @mayAlias03(
-; CHECK-NOT: add nsw <4 x i32>
-; CHECK: ret
-
-define i32 @mayAlias03(i32 %a) nounwind {
-entry:
- %a.addr = alloca i32, align 4
- %i = alloca i32, align 4
- store i32 %a, i32* %a.addr, align 4
- store i32 0, i32* %i, align 4
- br label %for.cond
-
-for.cond: ; preds = %for.inc, %entry
- %0 = load i32, i32* %i, align 4
- %cmp = icmp slt i32 %0, 100
- br i1 %cmp, label %for.body, label %for.end
-
-for.body: ; preds = %for.cond
- %1 = load i32*, i32** @PB, align 4
- %add.ptr = getelementptr inbounds i32, i32* %1, i32 100
- %2 = load i32, i32* %i, align 4
- %idx.neg = sub i32 0, %2
- %add.ptr1 = getelementptr inbounds i32, i32* %add.ptr, i32 %idx.neg
- %add.ptr2 = getelementptr inbounds i32, i32* %add.ptr1, i32 -1
- %3 = load i32, i32* %add.ptr2, align 4
- %4 = load i32, i32* %a.addr, align 4
- %add = add nsw i32 %3, %4
- %5 = load i32*, i32** @PA, align 4
- %6 = load i32, i32* %i, align 4
- %add.ptr3 = getelementptr inbounds i32, i32* %5, i32 %6
- store i32 %add, i32* %add.ptr3, align 4
- br label %for.inc
-
-for.inc: ; preds = %for.body
- %7 = load i32, i32* %i, align 4
- %inc = add nsw i32 %7, 1
- store i32 %inc, i32* %i, align 4
- br label %for.cond
-
-for.end: ; preds = %for.cond
- %8 = load i32*, i32** @PA, align 4
- %9 = load i32, i32* %a.addr, align 4
- %add.ptr4 = getelementptr inbounds i32, i32* %8, i32 %9
- %10 = load i32, i32* %add.ptr4, align 4
- ret i32 %10
-}
-
-;; === Finally, the tests that should only vectorize with care (or if we ignore undefined behaviour at all) ===
+;; === Ignore undefined behavior ===
-; int mustAlias01 (int a) {
+; int noAlias17(int a) {
; int i;
; for (i=0; i<SIZE; i++)
; Foo.A[i+10] = Foo.B[SIZE-i-1] + a;
; return Foo.A[a];
; }
-; CHECK-LABEL: define i32 @mustAlias01(
-; CHECK-NOT: add nsw <4 x i32>
+; CHECK-LABEL: define i32 @noAlias17(
+; CHECK: add nsw <4 x i32>
; CHECK: ret
-define i32 @mustAlias01(i32 %a) nounwind {
+define i32 @noAlias17(i32 %a) nounwind {
entry:
%a.addr = alloca i32, align 4
%i = alloca i32, align 4
@@ -977,17 +919,17 @@ for.end:
ret i32 %7
}
-; int mustAlias02 (int a) {
+; int noAlias18(int a) {
; int i;
; for (i=0; i<SIZE; i++)
; Foo.A[i] = Foo.B[SIZE-i-10] + a;
; return Foo.A[a];
; }
-; CHECK-LABEL: define i32 @mustAlias02(
-; CHECK-NOT: add nsw <4 x i32>
+; CHECK-LABEL: define i32 @noAlias18(
+; CHECK: add nsw <4 x i32>
; CHECK: ret
-define i32 @mustAlias02(i32 %a) nounwind {
+define i32 @noAlias18(i32 %a) nounwind {
entry:
%a.addr = alloca i32, align 4
%i = alloca i32, align 4
@@ -1026,17 +968,17 @@ for.end:
ret i32 %7
}
-; int mustAlias03 (int a) {
+; int noAlias19(int a) {
; int i;
; for (i=0; i<SIZE; i++)
; Foo.A[i+10] = Foo.B[SIZE-i-10] + a;
; return Foo.A[a];
; }
-; CHECK-LABEL: define i32 @mustAlias03(
-; CHECK-NOT: add nsw <4 x i32>
+; CHECK-LABEL: define i32 @noAlias19(
+; CHECK: add nsw <4 x i32>
; CHECK: ret
-define i32 @mustAlias03(i32 %a) nounwind {
+define i32 @noAlias19(i32 %a) nounwind {
entry:
%a.addr = alloca i32, align 4
%i = alloca i32, align 4
@@ -1075,3 +1017,57 @@ for.end:
%7 = load i32, i32* %arrayidx4, align 4
ret i32 %7
}
+
+; /// Pointer access, run-time check added
+; int mayAlias01 (int a) {
+; int i;
+; for (i=0; i<SIZE; i++)
+; *(PA+i) = *(PB+SIZE-i-1) + a;
+; return *(PA+a);
+; }
+; CHECK-LABEL: define i32 @mayAlias01(
+; CHECK-NOT: add nsw <4 x i32>
+; CHECK: ret
+
+define i32 @mayAlias01(i32 %a) nounwind {
+entry:
+ %a.addr = alloca i32, align 4
+ %i = alloca i32, align 4
+ store i32 %a, i32* %a.addr, align 4
+ store i32 0, i32* %i, align 4
+ br label %for.cond
+
+for.cond: ; preds = %for.inc, %entry
+ %0 = load i32, i32* %i, align 4
+ %cmp = icmp slt i32 %0, 100
+ br i1 %cmp, label %for.body, label %for.end
+
+for.body: ; preds = %for.cond
+ %1 = load i32*, i32** @PB, align 4
+ %add.ptr = getelementptr inbounds i32, i32* %1, i32 100
+ %2 = load i32, i32* %i, align 4
+ %idx.neg = sub i32 0, %2
+ %add.ptr1 = getelementptr inbounds i32, i32* %add.ptr, i32 %idx.neg
+ %add.ptr2 = getelementptr inbounds i32, i32* %add.ptr1, i32 -1
+ %3 = load i32, i32* %add.ptr2, align 4
+ %4 = load i32, i32* %a.addr, align 4
+ %add = add nsw i32 %3, %4
+ %5 = load i32*, i32** @PA, align 4
+ %6 = load i32, i32* %i, align 4
+ %add.ptr3 = getelementptr inbounds i32, i32* %5, i32 %6
+ store i32 %add, i32* %add.ptr3, align 4
+ br label %for.inc
+
+for.inc: ; preds = %for.body
+ %7 = load i32, i32* %i, align 4
+ %inc = add nsw i32 %7, 1
+ store i32 %inc, i32* %i, align 4
+ br label %for.cond
+
+for.end: ; preds = %for.cond
+ %8 = load i32*, i32** @PA, align 4
+ %9 = load i32, i32* %a.addr, align 4
+ %add.ptr4 = getelementptr inbounds i32, i32* %8, i32 %9
+ %10 = load i32, i32* %add.ptr4, align 4
+ ret i32 %10
+}
More information about the llvm-commits
mailing list