Add a CFL Alias Analysis implementation

This provides an implementation of CFL alias analysis (including some
supporting data structures). Currently, we don't have any extremely fancy
features, sans some interprocedural analysis (i.e. no field sensitivity, etc.),
and we do best sitting behind BasicAA + TBAA. In such a configuration, we take
~0.6-0.8% of total compile time, and give ~7-8% NoAlias responses to queries
TBAA and BasicAA couldn't answer when bootstrapping LLVM. In testing this on
other projects, we've seen up to 10.5% of queries dropped by BasicAA+TBAA
answered with NoAlias by this algorithm.

Patch by George Burgess IV (with minor modifications by me -- mostly adapting
some BasicAA tests), thanks!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216970 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/CFLAliasAnalysis/const-expr-gep.ll

@@ -0,0 +1,21 @@
+; This testcase consists of alias relations which should be completely
+; resolvable by cfl-aa, but require analysis of getelementptr constant exprs.
+; Derived from BasicAA/2003-12-11-ConstExprGEP.ll
+
+; RUN: opt < %s -cfl-aa -aa-eval -print-may-aliases -disable-output 2>&1 | FileCheck %s
+
+%T = type { i32, [10 x i8] }
+
+@G = external global %T
+
+; CHECK:     Function: test
+; CHECK-NOT:   May:
+
+define void @test() {
+  %D = getelementptr %T* @G, i64 0, i32 0
+  %E = getelementptr %T* @G, i64 0, i32 1, i64 5
+  %F = getelementptr i32* getelementptr (%T* @G, i64 0, i32 0), i64 0
+  %X = getelementptr [10 x i8]* getelementptr (%T* @G, i64 0, i32 1), i64 0, i64 5
+
+  ret void
+}

test/Analysis/CFLAliasAnalysis/constant-over-index.ll

@@ -0,0 +1,30 @@
+; RUN: opt < %s -cfl-aa -aa-eval -print-all-alias-modref-info 2>&1 | FileCheck %s
+
+; CFL AA currently returns PartialAlias, BasicAA returns MayAlias, both seem
+; acceptable (although we might decide that we don't want PartialAlias, and if
+; so, we should update this test case accordingly).
+; CHECK: {{PartialAlias|MayAlias}}: double* %p.0.i.0, double* %p3
+
+; %p3 is equal to %p.0.i.0 on the second iteration of the loop,
+; so MayAlias is needed.
+
+define void @foo([3 x [3 x double]]* noalias %p) {
+entry:
+  %p3 = getelementptr [3 x [3 x double]]* %p, i64 0, i64 0, i64 3
+  br label %loop
+
+loop:
+  %i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
+
+  %p.0.i.0 = getelementptr [3 x [3 x double]]* %p, i64 0, i64 %i, i64 0
+
+  store volatile double 0.0, double* %p3
+  store volatile double 0.1, double* %p.0.i.0
+
+  %i.next = add i64 %i, 1
+  %cmp = icmp slt i64 %i.next, 3
+  br i1 %cmp, label %loop, label %exit
+
+exit:
+  ret void
+}

test/Analysis/CFLAliasAnalysis/empty.ll

@@ -0,0 +1,12 @@
+; RUN: opt < %s -cfl-aa -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"
+
+; CHECK:      Function: foo:
+; CHECK-NEXT:   NoAlias: {}* %p, {}* %q
+
+define void @foo({}* %p, {}* %q) {
+  store {} {}, {}* %p
+  store {} {}, {}* %q
+  ret void
+}

test/Analysis/CFLAliasAnalysis/full-store-partial-alias.ll

@@ -0,0 +1,37 @@
+; RUN: opt -S -tbaa -cfl-aa -gvn < %s | FileCheck -check-prefix=CFLAA %s
+; RUN: opt -S -tbaa -gvn < %s | FileCheck %s
+; Adapted from the BasicAA full-store-partial-alias.ll test.
+
+; CFL AA should notice that the store stores to the entire %u object,
+; so the %tmp5 load is PartialAlias with the store and suppress TBAA.
+; Without CFL AA, TBAA should say that %tmp5 is NoAlias with the store.
+
+target datalayout = "e-p:64:64:64"
+
+%union.anon = type { double }
+
+@u = global %union.anon { double -2.500000e-01 }, align 8
+@endianness_test = global i64 1, align 8
+
+define i32 @signbit(double %x) nounwind {
+; CFLAA: ret i32 %tmp5.lobit
+; CHECK:   ret i32 0
+entry:
+  %u = alloca %union.anon, align 8
+  %tmp9 = getelementptr inbounds %union.anon* %u, i64 0, i32 0
+  store double %x, double* %tmp9, align 8, !tbaa !0
+  %tmp2 = load i32* bitcast (i64* @endianness_test to i32*), align 8, !tbaa !3
+  %idxprom = sext i32 %tmp2 to i64
+  %tmp4 = bitcast %union.anon* %u to [2 x i32]*
+  %arrayidx = getelementptr inbounds [2 x i32]* %tmp4, i64 0, i64 %idxprom
+  %tmp5 = load i32* %arrayidx, align 4, !tbaa !3
+  %tmp5.lobit = lshr i32 %tmp5, 31
+  ret i32 %tmp5.lobit
+}
+
+!0 = metadata !{metadata !4, metadata !4, i64 0}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA", null}
+!3 = metadata !{metadata !5, metadata !5, i64 0}
+!4 = metadata !{metadata !"double", metadata !1}
+!5 = metadata !{metadata !"int", metadata !1}

test/Analysis/CFLAliasAnalysis/gep-signed-arithmetic.ll

@@ -0,0 +1,17 @@
+; RUN: opt < %s -cfl-aa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+; Derived from BasicAA/2010-09-15-GEP-SignedArithmetic.ll
+
+target datalayout = "e-p:32:32:32"
+
+; CHECK: 1 partial alias response
+
+define i32 @test(i32* %tab, i32 %indvar) nounwind {
+  %tmp31 = mul i32 %indvar, -2
+  %tmp32 = add i32 %tmp31, 30
+  %t.5 = getelementptr i32* %tab, i32 %tmp32
+  %loada = load i32* %tab
+  store i32 0, i32* %t.5
+  %loadb = load i32* %tab
+  %rval = add i32 %loada, %loadb
+  ret i32 %rval
+}

test/Analysis/CFLAliasAnalysis/must-and-partial.ll

@@ -0,0 +1,39 @@
+; RUN: opt < %s -cfl-aa -aa-eval -print-all-alias-modref-info 2>&1 | FileCheck %s
+
+; When merging MustAlias and PartialAlias, merge to PartialAlias
+; instead of MayAlias.
+
+
+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"
+
+; CHECK: PartialAlias:  i16* %bigbase0, i8* %phi
+define i8 @test0(i8* %base, i1 %x) {
+entry:
+  %baseplusone = getelementptr i8* %base, i64 1
+  br i1 %x, label %red, label %green
+red:
+  br label %green
+green:
+  %phi = phi i8* [ %baseplusone, %red ], [ %base, %entry ]
+  store i8 0, i8* %phi
+
+  %bigbase0 = bitcast i8* %base to i16*
+  store i16 -1, i16* %bigbase0
+
+  %loaded = load i8* %phi
+  ret i8 %loaded
+}
+
+; CHECK: PartialAlias:  i16* %bigbase1, i8* %sel
+define i8 @test1(i8* %base, i1 %x) {
+entry:
+  %baseplusone = getelementptr i8* %base, i64 1
+  %sel = select i1 %x, i8* %baseplusone, i8* %base
+  store i8 0, i8* %sel
+
+  %bigbase1 = bitcast i8* %base to i16*
+  store i16 -1, i16* %bigbase1
+
+  %loaded = load i8* %sel
+  ret i8 %loaded
+}

test/Analysis/CFLAliasAnalysis/phi-and-select.ll

@@ -0,0 +1,36 @@
+; RUN: opt < %s -cfl-aa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+; Derived from (a subset of) BasicAA/phi-and-select.ll 
+
+; CHECK: Function: qux
+; CHECK:  NoAlias: double* %a, double* %b
+; CHECK: ===== Alias Analysis Evaluator Report =====
+
+; Two PHIs with disjoint sets of inputs.
+define void @qux(i1 %m, double* noalias %x, double* noalias %y,
+                 i1 %n, double* noalias %v, double* noalias %w) {
+entry:
+  br i1 %m, label %true, label %false
+
+true:
+  br label %exit
+
+false:
+  br label %exit
+
+exit:
+  %a = phi double* [ %x, %true ], [ %y, %false ]
+  br i1 %n, label %ntrue, label %nfalse
+
+ntrue:
+  br label %nexit
+
+nfalse:
+  br label %nexit
+
+nexit:
+  %b = phi double* [ %v, %ntrue ], [ %w, %nfalse ]
+  store volatile double 0.0, double* %a
+  store volatile double 1.0, double* %b
+  ret void
+}
+

test/Analysis/CFLAliasAnalysis/simple.ll

@@ -0,0 +1,18 @@
+; This testcase consists of alias relations which should be completely
+; resolvable by cfl-aa (derived from BasicAA/2003-11-04-SimpleCases.ll).
+
+; RUN: opt < %s -cfl-aa -aa-eval -print-may-aliases -disable-output 2>&1 | FileCheck %s
+
+%T = type { i32, [10 x i8] }
+
+; CHECK:     Function: test
+; CHECK-NOT:   May:
+
+define void @test(%T* %P) {
+  %A = getelementptr %T* %P, i64 0
+  %B = getelementptr %T* %P, i64 0, i32 0
+  %C = getelementptr %T* %P, i64 0, i32 1
+  %D = getelementptr %T* %P, i64 0, i32 1, i64 0
+  %E = getelementptr %T* %P, i64 0, i32 1, i64 5
+  ret void
+}