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GlobalsAA: Take advantage of ArgMemOnly, InaccessibleMemOnly and InaccessibleMemOrArgMemOnly attributes

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Summary:
1. Modify AnalyzeCallGraph() to retain function info for external functions
if the function has [InaccessibleMemOr]ArgMemOnly flags.
2. When analyzing the use of a global is function parameter at a call site,
mark the callee also as modifying the global appropriately.
3. Add additional test cases.

Depends on D15499

Reviewers: hfinkel, jmolloy

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15605

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Vaivaswatha Nagaraj 2015-12-18 11:02:52 +00:00
parent 35e39f0c8a
commit 5a9e526f29
3 changed files with 83 additions and 1 deletions
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17
lib/Analysis/GlobalsModRef.cpp
View File

@ -376,6 +376,15 @@ bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
} else {
return true; // Argument of an unknown call.
}
// If the Callee is not ReadNone, it may read the global,
// and if it is not ReadOnly, it may also write to it.
Function *CalleeF = CS.getCalledFunction();
if (!CalleeF->doesNotAccessMemory()) {
if (Readers)
Readers->insert(CalleeF);
if (Writers && !CalleeF->onlyReadsMemory())
Writers->insert(CalleeF);
}
}
} else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
@ -507,7 +516,7 @@ void GlobalsAAResult::AnalyzeCallGraph(CallGraph &CG, Module &M) {
if (F->isDeclaration()) {
// Try to get mod/ref behaviour from function attributes.
if (F->doesNotAccessMemory()) {
if (F->doesNotAccessMemory() || F->onlyAccessesInaccessibleMemory()) {
// Can't do better than that!
} else if (F->onlyReadsMemory()) {
FI.addModRefInfo(MRI_Ref);
@ -515,6 +524,12 @@ void GlobalsAAResult::AnalyzeCallGraph(CallGraph &CG, Module &M) {
// This function might call back into the module and read a global -
// consider every global as possibly being read by this function.
FI.setMayReadAnyGlobal();
} else if (F->onlyAccessesArgMemory() ||
F->onlyAccessesInaccessibleMemOrArgMem()) {
// This function may only access (read/write) memory pointed to by its
// arguments. If this pointer is to a global, this escaping use of the
// pointer is captured in AnalyzeUsesOfPointer().
FI.addModRefInfo(MRI_ModRef);
} else {
FI.addModRefInfo(MRI_ModRef);
// Can't say anything useful unless it's an intrinsic - they don't

47
test/Analysis/GlobalsModRef/argmemonly-escape.ll Normal file
View File

@ -0,0 +1,47 @@
; RUN: opt < %s -O1 -S -enable-non-lto-gmr=true | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.10.0"
@a = internal global [3 x i32] zeroinitializer, align 4
; The important thing we're checking for here is the reload of (some element of)
; @a after the memset.
; CHECK-LABEL: @main
; CHECK: load i32, i32* getelementptr {{.*}} @a
; CHECK-NEXT: call void @memsetp0i8i64{{.*}} @a
; CHECK-NEXT: load i32, i32* getelementptr {{.*}} @a
; CHECK-NEXT: call void @memsetp0i8i64A{{.*}} @a
; CHECK-NEXT: load i32, i32* getelementptr {{.*}} @a
; CHECK: icmp eq
; CHECK: br i1
define i32 @main() {
entry:
%0 = bitcast [3 x i32]* @a to i8*
%1 = load i32, i32* getelementptr inbounds ([3 x i32], [3 x i32]* @a, i64 0, i64 2), align 4
call void @memsetp0i8i64(i8* %0, i8 0, i64 4, i32 4, i1 false)
%2 = load i32, i32* getelementptr inbounds ([3 x i32], [3 x i32]* @a, i64 0, i64 2), align 4
call void @memsetp0i8i64A(i8* %0, i8 0, i64 4, i32 4, i1 false)
%3 = load i32, i32* getelementptr inbounds ([3 x i32], [3 x i32]* @a, i64 0, i64 2), align 4
%4 = add i32 %2, %3
%cmp1 = icmp eq i32 %1, %4
br i1 %cmp1, label %if.then, label %if.end
if.then: ; preds = %entr
call void @abort() #3
unreachable
if.end: ; preds = %entry
ret i32 0
}
; Function Attrs: nounwind argmemonly
declare void @memsetp0i8i64(i8* nocapture, i8, i64, i32, i1) nounwind argmemonly
; Function Attrs: nounwind inaccessiblemem_or_argmemonly
declare void @memsetp0i8i64A(i8* nocapture, i8, i64, i32, i1) nounwind inaccessiblemem_or_argmemonly
; Function Attrs: noreturn nounwind
declare void @abort() noreturn nounwind

20
test/Analysis/GlobalsModRef/modreftest.ll
View File

@ -16,3 +16,23 @@ define i32 @test(i32* %P) {
define void @doesnotmodX() {
ret void
}
declare void @InaccessibleMemOnlyFunc( ) #0
declare void @InaccessibleMemOrArgMemOnlyFunc( ) #1
define i32 @test2(i32* %P) {
; CHECK: @test2
; CHECK-NEXT: store i32 12, i32* @X
; CHECK-NEXT: call void @InaccessibleMemOnlyFunc()
; CHECK-NEXT: call void @InaccessibleMemOrArgMemOnlyFunc()
; CHECK-NOT: load i32
; CHECK-NEXT: ret i32 12
store i32 12, i32* @X
call void @InaccessibleMemOnlyFunc( )
call void @InaccessibleMemOrArgMemOnlyFunc( )
%V = load i32, i32* @X ; <i32> [#uses=1]
ret i32 %V
}
attributes #0 = { inaccessiblememonly }
attributes #1 = { inaccessiblemem_or_argmemonly }