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This patch extends the OptimizeGlobalAddressOfMalloc to handle the null check of global pointer variables. It is disabled with https://reviews.llvm.org/rGb7cd291c1542aee12c9e9fde6c411314a163a8ea. This PR is to reenable it while fixing the original problem reported. The fix is to set the store value correctly when creating store for the new created global init bool symbol.

Browse Source 
Reviewed By: efriedma

Differential Revision:  https://reviews.llvm.org/D102711
This commit is contained in:
Shimin Cui 2021-07-20 12:27:26 -04:00
parent a2254d3fcc
commit 74b9048a41
4 changed files with 127 additions and 14 deletions
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34
lib/Transforms/IPO/GlobalOpt.cpp
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@ -699,6 +699,16 @@ static bool AllUsesOfValueWillTrapIfNull(const Value *V,
// checked.
if (PHIs.insert(PN).second && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
return false;
} else if (isa<ICmpInst>(U) &&
!ICmpInst::isSigned(cast<ICmpInst>(U)->getPredicate()) &&
isa<LoadInst>(U->getOperand(0)) &&
isa<ConstantPointerNull>(U->getOperand(1))) {
assert(isa<GlobalValue>(
cast<LoadInst>(U->getOperand(0))->getPointerOperand()) &&
"Should be GlobalVariable");
// This and only this kind of non-signed ICmpInst is to be replaced with
// the comparing of the value of the created global init bool later in
// optimizeGlobalAddressOfMalloc for the global variable.
} else {
//cerr << "NONTRAPPING USE: " << *U;
return false;
@ -940,9 +950,13 @@ OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, CallInst *CI, Type *AllocTy,
// Loop over all uses of GV, processing them in turn.
while (!GV->use_empty()) {
if (StoreInst *SI = dyn_cast<StoreInst>(GV->user_back())) {
// The global is initialized when the store to it occurs.
new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false,
Align(1), SI->getOrdering(), SI->getSyncScopeID(), SI);
// The global is initialized when the store to it occurs. If the stored
// value is null value, the global bool is set to false, otherwise true.
new StoreInst(ConstantInt::getBool(
GV->getContext(),
!isa<ConstantPointerNull>(SI->getValueOperand())),
InitBool, false, Align(1), SI->getOrdering(),
SI->getSyncScopeID(), SI);
SI->eraseFromParent();
continue;
}
@ -957,28 +971,24 @@ OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, CallInst *CI, Type *AllocTy,
}
// Replace the cmp X, 0 with a use of the bool value.
// Sink the load to where the compare was, if atomic rules allow us to.
Value *LV = new LoadInst(InitBool->getValueType(), InitBool,
InitBool->getName() + ".val", false, Align(1),
LI->getOrdering(), LI->getSyncScopeID(),
LI->isUnordered() ? (Instruction *)ICI : LI);
LI->getOrdering(), LI->getSyncScopeID(), LI);
InitBoolUsed = true;
switch (ICI->getPredicate()) {
default: llvm_unreachable("Unknown ICmp Predicate!");
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT: // X < null -> always false
case ICmpInst::ICMP_ULT: // X < null -> always false
LV = ConstantInt::getFalse(GV->getContext());
break;
case ICmpInst::ICMP_UGE: // X >= null -> always true
LV = ConstantInt::getTrue(GV->getContext());
break;
case ICmpInst::ICMP_ULE:
case ICmpInst::ICMP_SLE:
case ICmpInst::ICMP_EQ:
LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
break;
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_UGE:
case ICmpInst::ICMP_SGE:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
break; // no change.
}
ICI->replaceAllUsesWith(LV);

51
test/Transforms/GlobalOpt/malloc-promote-4.ll Normal file
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@ -0,0 +1,51 @@
; RUN: opt -S -globalopt -o - < %s | FileCheck %s
; CHECK: [[G_INIT:@.*]] = internal unnamed_addr global i1 false
@g = internal global i32* null, align 8
; CHECK-LABEL: define {{.*}} @f1(
; CHECK-NEXT: [[G_INIT_VAL:%.*]] = load i1, i1* [[G_INIT]], align 1
; CHECK-NEXT: call fastcc void @f2()
; CHECK-NEXT: [[NOTINIT:%.*]] = xor i1 [[G_INIT_VAL]], true
; CHECK-NEXT: br i1 [[NOTINIT]], label [[TMP1:%.*]], label [[TMP2:%.*]]
;
define internal i32 @f1() {
%1 = load i32*, i32** @g, align 8
call void @f2();
%2 = icmp eq i32* %1, null
br i1 %2, label %3, label %4
3: ; preds = %0
br label %5
4: ; preds = %0
br label %5
5: ; preds = %3, %4
%6 = phi i32 [ -1, %3 ], [ 1, %4 ]
ret i32 %6
}
; CHECK-LABEL: define {{.*}} @f2(
; CHECK-NEXT: store i1 true, i1* [[G_INIT]], align 1
; CHECK-NEXT: ret void
;
define internal void @f2() {
%1 = call noalias i8* @malloc(i64 4)
%2 = bitcast i8* %1 to i32*
store i32* %2, i32** @g, align 8
ret void
}
; CHECK-LABEL: define {{.*}} @main(
; CHECK-NEXT: store i1 false, i1* [[G_INIT]], align 1
; CHECK-NEXT: [[TMP1:%.*]] = call fastcc i32 @f1()
; CHECK-NEXT: ret i32 [[TMP1]]
;
define dso_local i32 @main() {
store i32* null, i32** @g, align 8
%1 = call i32 @f1()
ret i32 %1
}
declare dso_local noalias i8* @malloc(i64)

10
test/Transforms/GlobalOpt/null-check-is-use-pr35760.ll
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@ -3,10 +3,13 @@
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; CHECK: [[_ZL3G_I_INIT:@.*]] = internal unnamed_addr global i1 false
@_ZL3g_i = internal global i32* null, align 8
@.str = private unnamed_addr constant [2 x i8] c"0\00", align 1
@.str.1 = private unnamed_addr constant [2 x i8] c"1\00", align 1
; CHECK-LABEL: define {{.*}} @main(
; CHECK-NEXT: store i1 false, i1* [[_ZL3G_I_INIT]], align 1
define dso_local i32 @main() {
store i32* null, i32** @_ZL3g_i, align 8
call void @_ZL13PutsSomethingv()
@ -14,8 +17,11 @@ define dso_local i32 @main() {
}
; CHECK-LABEL: define {{.*}} @_ZL13PutsSomethingv()
; CHECK: [[gvLoad:%.*]] = load i32*, i32** @_ZL3g_i
; CHECK-NEXT: icmp eq i32* [[gvLoad]], null
; CHECK-NEXT: [[_ZL3G_I_INIT_VAL:%.*]] = load i1, i1* [[_ZL3G_I_INIT]], align 1
; CHECK-NEXT: [[NOTINIT:%.*]] = xor i1 [[_ZL3G_I_INIT_VAL]], true
; CHECK-NEXT: br i1 [[NOTINIT]], label %[[TMP1:.*]], label %[[TMP3:.*]]
; CHECK: [[TMP1]]:
; CHECK-NEXT: store i1 true, i1* [[_ZL3G_I_INIT]], align 1
define internal void @_ZL13PutsSomethingv() {
%1 = load i32*, i32** @_ZL3g_i, align 8
%2 = icmp eq i32* %1, null

46
test/Transforms/GlobalOpt/null-check-not-use-pr35760.ll Normal file
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@ -0,0 +1,46 @@
; RUN: opt -S -globalopt -o - < %s | FileCheck %s
; No malloc promotion with non-null check.
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@_ZL3g_i = internal global i32* null, align 8
@_ZL3g_j = global i32* null, align 8
@.str = private unnamed_addr constant [2 x i8] c"0\00", align 1
@.str.1 = private unnamed_addr constant [2 x i8] c"1\00", align 1
define dso_local i32 @main() {
store i32* null, i32** @_ZL3g_i, align 8
call void @_ZL13PutsSomethingv()
ret i32 0
}
; CHECK-LABEL: define {{.*}} @_ZL13PutsSomethingv()
; CHECK-NEXT: [[TMP1:%.*]] = load i32*, i32** @_ZL3g_i, align 8
; CHECK-NEXT: [[TMP2:%.*]] = load i32*, i32** @_ZL3g_j, align 8
; CHECK-NEXT: icmp eq i32* [[TMP1]], [[TMP2]]
define internal void @_ZL13PutsSomethingv() {
%1 = load i32*, i32** @_ZL3g_i, align 8
%2 = load i32*, i32** @_ZL3g_j, align 8
%cmp = icmp eq i32* %1, %2
br i1 %cmp, label %3, label %7
3: ; preds = %0
%4 = call noalias i8* @malloc(i64 4) #3
%5 = bitcast i8* %4 to i32*
store i32* %5, i32** @_ZL3g_i, align 8
%6 = call i32 @puts(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i64 0, i64 0))
br label %9
7: ; preds = %0
%8 = call i32 @puts(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str.1, i64 0, i64 0))
br label %9
9: ; preds = %7, %3
ret void
}
declare dso_local noalias i8* @malloc(i64)
declare dso_local i32 @puts(i8* nocapture readonly)