[llvm] r211331 - Don't build switch lookup tables for dllimport or TLS variables
Hans Wennborg
hans at hanshq.net
Thu Jun 19 17:38:12 PDT 2014
Author: hans
Date: Thu Jun 19 19:38:12 2014
New Revision: 211331
URL: http://llvm.org/viewvc/llvm-project?rev=211331&view=rev
Log:
Don't build switch lookup tables for dllimport or TLS variables
We would previously put dllimport variables in switch lookup tables, which
doesn't work because the address cannot be used in a constant initializer.
This is basically the same problem that we have in PR19955.
Putting TLS variables in switch tables also desn't work, because the
address of such a variable is not constant.
Differential Revision: http://reviews.llvm.org/D4220
Modified:
llvm/trunk/include/llvm/IR/Constant.h
llvm/trunk/lib/IR/Constants.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
Modified: llvm/trunk/include/llvm/IR/Constant.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Constant.h?rev=211331&r1=211330&r2=211331&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Constant.h (original)
+++ llvm/trunk/include/llvm/IR/Constant.h Thu Jun 19 19:38:12 2014
@@ -71,6 +71,9 @@ public:
/// isThreadDependent - Return true if the value can vary between threads.
bool isThreadDependent() const;
+ /// Return true if the value is dependent on a dllimport variable.
+ bool isDLLImportDependent() const;
+
/// isConstantUsed - Return true if the constant has users other than constant
/// exprs and other dangling things.
bool isConstantUsed() const;
Modified: llvm/trunk/lib/IR/Constants.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Constants.cpp?rev=211331&r1=211330&r2=211331&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Constants.cpp (original)
+++ llvm/trunk/lib/IR/Constants.cpp Thu Jun 19 19:38:12 2014
@@ -278,35 +278,48 @@ bool Constant::canTrap() const {
return canTrapImpl(this, NonTrappingOps);
}
-/// isThreadDependent - Return true if the value can vary between threads.
-bool Constant::isThreadDependent() const {
- SmallPtrSet<const Constant*, 64> Visited;
- SmallVector<const Constant*, 64> WorkList;
- WorkList.push_back(this);
- Visited.insert(this);
+/// Check if C contains a GlobalValue for which Predicate is true.
+static bool
+ConstHasGlobalValuePredicate(const Constant *C,
+ bool (*Predicate)(const GlobalValue *)) {
+ SmallPtrSet<const Constant *, 8> Visited;
+ SmallVector<const Constant *, 8> WorkList;
+ WorkList.push_back(C);
+ Visited.insert(C);
while (!WorkList.empty()) {
- const Constant *C = WorkList.pop_back_val();
-
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
- if (GV->isThreadLocal())
+ const Constant *WorkItem = WorkList.pop_back_val();
+ if (const auto *GV = dyn_cast<GlobalValue>(WorkItem))
+ if (Predicate(GV))
return true;
- }
-
- for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I) {
- const Constant *D = dyn_cast<Constant>(C->getOperand(I));
- if (!D)
+ for (const Value *Op : WorkItem->operands()) {
+ const Constant *ConstOp = dyn_cast<Constant>(Op);
+ if (!ConstOp)
continue;
- if (Visited.insert(D))
- WorkList.push_back(D);
+ if (Visited.insert(ConstOp))
+ WorkList.push_back(ConstOp);
}
}
-
return false;
}
-/// isConstantUsed - Return true if the constant has users other than constant
-/// exprs and other dangling things.
+/// Return true if the value can vary between threads.
+bool Constant::isThreadDependent() const {
+ auto DLLImportPredicate = [](const GlobalValue *GV) {
+ return GV->isThreadLocal();
+ };
+ return ConstHasGlobalValuePredicate(this, DLLImportPredicate);
+}
+
+bool Constant::isDLLImportDependent() const {
+ auto DLLImportPredicate = [](const GlobalValue *GV) {
+ return GV->hasDLLImportStorageClass();
+ };
+ return ConstHasGlobalValuePredicate(this, DLLImportPredicate);
+}
+
+/// Return true if the constant has users other than constant exprs and other
+/// dangling things.
bool Constant::isConstantUsed() const {
for (const User *U : users()) {
const Constant *UC = dyn_cast<Constant>(U);
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=211331&r1=211330&r2=211331&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Jun 19 19:38:12 2014
@@ -3313,6 +3313,10 @@ static bool ForwardSwitchConditionToPHI(
static bool ValidLookupTableConstant(Constant *C) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
return CE->isGEPWithNoNotionalOverIndexing();
+ if (C->isThreadDependent())
+ return false;
+ if (C->isDLLImportDependent())
+ return false;
return isa<ConstantFP>(C) ||
isa<ConstantInt>(C) ||
Modified: llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll?rev=211331&r1=211330&r2=211331&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll Thu Jun 19 19:38:12 2014
@@ -918,3 +918,55 @@ return:
; CHECK: switch i32
; CHECK-NOT: @switch.table
}
+
+; Don't build tables for switches with TLS variables.
+ at tls_a = thread_local global i32 0
+ at tls_b = thread_local global i32 0
+ at tls_c = thread_local global i32 0
+ at tls_d = thread_local global i32 0
+define i32* @tls(i32 %x) {
+entry:
+ switch i32 %x, label %sw.default [
+ i32 0, label %return
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ ]
+sw.bb1:
+ br label %return
+sw.bb2:
+ br label %return
+sw.default:
+ br label %return
+return:
+ %retval.0 = phi i32* [ @tls_d, %sw.default ], [ @tls_c, %sw.bb2 ], [ @tls_b, %sw.bb1 ], [ @tls_a, %entry ]
+ ret i32* %retval.0
+; CHECK-LABEL: @tls(
+; CHECK: switch i32
+; CHECK-NOT: @switch.table
+}
+
+; Don't build tables for switches with dllimport variables.
+ at dllimport_a = external dllimport global i32
+ at dllimport_b = external dllimport global i32
+ at dllimport_c = external dllimport global i32
+ at dllimport_d = external dllimport global i32
+define i32* @dllimport(i32 %x) {
+entry:
+ switch i32 %x, label %sw.default [
+ i32 0, label %return
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ ]
+sw.bb1:
+ br label %return
+sw.bb2:
+ br label %return
+sw.default:
+ br label %return
+return:
+ %retval.0 = phi i32* [ @dllimport_d, %sw.default ], [ @dllimport_c, %sw.bb2 ], [ @dllimport_b, %sw.bb1 ], [ @dllimport_a, %entry ]
+ ret i32* %retval.0
+; CHECK-LABEL: @dllimport(
+; CHECK: switch i32
+; CHECK-NOT: @switch.table
+}
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