From bd12a322d7e0b2541880c00f5551e047e06be982 Mon Sep 17 00:00:00 2001 From: Florian Hahn Date: Thu, 12 Dec 2019 17:10:43 +0000 Subject: [PATCH] [BasicAA] Use GEP as context for computeKnownBits in aliasGEP. In order to use assumptions, computeKnownBits needs a context instruction. We can use the GEP, if it is an instruction. We already pass the assumption cache, but it cannot be used without a context instruction. Reviewers: anemet, asbirlea, hfinkel, spatel Reviewed By: asbirlea Differential Revision: https://reviews.llvm.org/D71264 --- llvm/lib/Analysis/BasicAliasAnalysis.cpp | 3 +- .../test/Analysis/BasicAA/assume-index-positive.ll | 116 +++++++++++++++++++++ 2 files changed, 118 insertions(+), 1 deletion(-) create mode 100644 llvm/test/Analysis/BasicAA/assume-index-positive.ll diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp index 227b12d..e852d66 100644 --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp @@ -1482,7 +1482,8 @@ AliasResult BasicAAResult::aliasGEP( // give up if we can't determine conditions that hold for every cycle: const Value *V = DecompGEP1.VarIndices[i].V; - KnownBits Known = computeKnownBits(V, DL, 0, &AC, nullptr, DT); + KnownBits Known = + computeKnownBits(V, DL, 0, &AC, dyn_cast(GEP1), DT); bool SignKnownZero = Known.isNonNegative(); bool SignKnownOne = Known.isNegative(); diff --git a/llvm/test/Analysis/BasicAA/assume-index-positive.ll b/llvm/test/Analysis/BasicAA/assume-index-positive.ll new file mode 100644 index 0000000..d89738a --- /dev/null +++ b/llvm/test/Analysis/BasicAA/assume-index-positive.ll @@ -0,0 +1,116 @@ +; RUN: opt -basicaa -aa-eval -print-all-alias-modref-info %s 2>&1 | FileCheck %s + +; %col.ptr.1 and %col.ptr.2 do not alias, if we know that %skip >= 0, because +; the distance between %col.ptr.1 and %col.ptr.2 is %skip + 6 and we load 6 +; elements. +define void @test1(double* %ptr, i32 %skip) { +; CHECK-LABEL: Function: test1: 4 pointers, 1 call sites +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.1, double* %ptr +; CHECK-NEXT: NoAlias: double* %col.ptr.2, double* %ptr +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.1, double* %col.ptr.2 +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.2.cast, double* %ptr +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.1, <6 x double>* %col.ptr.2.cast +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.2.cast, double* %col.ptr.2 +; CHECK-NEXT: NoModRef: Ptr: double* %ptr <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.1 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: double* %col.ptr.2 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.2.cast <-> call void @llvm.assume(i1 %gt) +; + %gt = icmp sgt i32 %skip, -1 + call void @llvm.assume(i1 %gt) + %stride = add nsw nuw i32 %skip, 6 + %col.ptr.1 = bitcast double* %ptr to <6 x double>* + %lv.1 = load <6 x double>, <6 x double>* %col.ptr.1, align 8 + %col.ptr.2= getelementptr double, double* %ptr, i32 %stride + %col.ptr.2.cast = bitcast double* %col.ptr.2 to <6 x double>* + %lv.2 = load <6 x double>, <6 x double>* %col.ptr.2.cast, align 8 + %res.1 = fadd <6 x double> %lv.1, %lv.1 + %res.2 = fadd <6 x double> %lv.2, %lv.2 + store <6 x double> %res.1, <6 x double>* %col.ptr.1, align 8 + store <6 x double> %res.2, <6 x double>* %col.ptr.2.cast, align 8 + ret void +} + +; Same as @test1, but now we do not have an assume guaranteeing %skip >= 0. +define void @test2(double* %ptr, i32 %skip) { +; CHECK-LABEL: Function: test2: 4 pointers, 0 call sites +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.1, double* %ptr +; CHECK-NEXT: MayAlias: double* %col.ptr.2, double* %ptr +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.1, double* %col.ptr.2 +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.2.cast, double* %ptr +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.1, <6 x double>* %col.ptr.2.cast +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.2.cast, double* %col.ptr.2 +; + %stride = add nsw nuw i32 %skip, 6 + %col.ptr.1 = bitcast double* %ptr to <6 x double>* + %lv.1 = load <6 x double>, <6 x double>* %col.ptr.1, align 8 + %col.ptr.2= getelementptr double, double* %ptr, i32 %stride + %col.ptr.2.cast = bitcast double* %col.ptr.2 to <6 x double>* + %lv.2 = load <6 x double>, <6 x double>* %col.ptr.2.cast, align 8 + %res.1 = fadd <6 x double> %lv.1, %lv.1 + %res.2 = fadd <6 x double> %lv.2, %lv.2 + store <6 x double> %res.1, <6 x double>* %col.ptr.1, align 8 + store <6 x double> %res.2, <6 x double>* %col.ptr.2.cast, align 8 + ret void +} + +; Same as @test1, but the assume just guarantees %skip > -3, which is not +; enough to derive NoAlias +define void @test3(double* %ptr, i32 %skip) { +; CHECK-LABEL: Function: test3: 4 pointers, 1 call sites +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.1, double* %ptr +; CHECK-NEXT: MayAlias: double* %col.ptr.2, double* %ptr +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.1, double* %col.ptr.2 +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.2.cast, double* %ptr +; CHECK-NEXT: MayAlias: <6 x double>* %col.ptr.1, <6 x double>* %col.ptr.2.cast +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.2.cast, double* %col.ptr.2 +; CHECK-NEXT: NoModRef: Ptr: double* %ptr <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.1 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: double* %col.ptr.2 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.2.cast <-> call void @llvm.assume(i1 %gt) +; + %gt = icmp sgt i32 %skip, -3 + call void @llvm.assume(i1 %gt) + %stride = add nsw nuw i32 %skip, 6 + %col.ptr.1 = bitcast double* %ptr to <6 x double>* + %lv.1 = load <6 x double>, <6 x double>* %col.ptr.1, align 8 + %col.ptr.2= getelementptr double, double* %ptr, i32 %stride + %col.ptr.2.cast = bitcast double* %col.ptr.2 to <6 x double>* + %lv.2 = load <6 x double>, <6 x double>* %col.ptr.2.cast, align 8 + %res.1 = fadd <6 x double> %lv.1, %lv.1 + %res.2 = fadd <6 x double> %lv.2, %lv.2 + store <6 x double> %res.1, <6 x double>* %col.ptr.1, align 8 + store <6 x double> %res.2, <6 x double>* %col.ptr.2.cast, align 8 + ret void +} + +; Same as @test1, but the assume uses the sge predicate for %skip >= 0. +define void @test4(double* %ptr, i32 %skip) { +; CHECK-LABEL: Function: test4: 4 pointers, 1 call sites +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.1, double* %ptr +; CHECK-NEXT: NoAlias: double* %col.ptr.2, double* %ptr +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.1, double* %col.ptr.2 +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.2.cast, double* %ptr +; CHECK-NEXT: NoAlias: <6 x double>* %col.ptr.1, <6 x double>* %col.ptr.2.cast +; CHECK-NEXT: MustAlias: <6 x double>* %col.ptr.2.cast, double* %col.ptr.2 +; CHECK-NEXT: NoModRef: Ptr: double* %ptr <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.1 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: double* %col.ptr.2 <-> call void @llvm.assume(i1 %gt) +; CHECK-NEXT: NoModRef: Ptr: <6 x double>* %col.ptr.2.cast <-> call void @llvm.assume(i1 %gt) +; + %gt = icmp sge i32 %skip, 0 + call void @llvm.assume(i1 %gt) + %stride = add nsw nuw i32 %skip, 6 + %col.ptr.1 = bitcast double* %ptr to <6 x double>* + %lv.1 = load <6 x double>, <6 x double>* %col.ptr.1, align 8 + %col.ptr.2= getelementptr double, double* %ptr, i32 %stride + %col.ptr.2.cast = bitcast double* %col.ptr.2 to <6 x double>* + %lv.2 = load <6 x double>, <6 x double>* %col.ptr.2.cast, align 8 + %res.1 = fadd <6 x double> %lv.1, %lv.1 + %res.2 = fadd <6 x double> %lv.2, %lv.2 + store <6 x double> %res.1, <6 x double>* %col.ptr.1, align 8 + store <6 x double> %res.2, <6 x double>* %col.ptr.2.cast, align 8 + ret void +} + +declare void @llvm.assume(i1 %cond) -- 2.7.4