efriedma updated this revision to Diff 466657.
efriedma added a comment.
Upload correct version of patch
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https://reviews.llvm.org/D135628/new/
https://reviews.llvm.org/D135628
Files:
clang/lib/CodeGen/ItaniumCXXABI.cpp
clang/test/CodeGenCXX/threadsafe-statics-no-atomic.cpp
Index: clang/test/CodeGenCXX/threadsafe-statics-no-atomic.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/threadsafe-statics-no-atomic.cpp
@@ -0,0 +1,21 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -emit-llvm -triple=thumbv6m-eabi -o - %s | FileCheck %s
+
+int f();
+
+// CHECK-LABEL: @_Z1gv(
+// CHECK-NEXT: entry:
+// CHECK-NEXT: [[TMP0:%.*]] = call i32 @__cxa_guard_acquire(ptr @_ZGVZ1gvE1a) #[[ATTR1:[0-9]+]]
+// CHECK-NEXT: [[TOBOOL:%.*]] = icmp ne i32 [[TMP0]], 0
+// CHECK-NEXT: br i1 [[TOBOOL]], label [[INIT:%.*]], label [[INIT_END:%.*]]
+// CHECK: init:
+// CHECK-NEXT: [[CALL:%.*]] = call noundef i32 @_Z1fv()
+// CHECK-NEXT: store i32 [[CALL]], ptr @_ZZ1gvE1a, align 4
+// CHECK-NEXT: call void @__cxa_guard_release(ptr @_ZGVZ1gvE1a) #[[ATTR1]]
+// CHECK-NEXT: br label [[INIT_END]]
+// CHECK: init.end:
+// CHECK-NEXT: ret void
+//
+void g() {
+ static int a = f();
+}
Index: clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2428,54 +2428,61 @@
// __cxa_guard_release (&obj_guard);
// }
// }
-
- // Load the first byte of the guard variable.
- llvm::LoadInst *LI =
- Builder.CreateLoad(Builder.CreateElementBitCast(guardAddr, CGM.Int8Ty));
-
- // Itanium ABI:
- // An implementation supporting thread-safety on multiprocessor
- // systems must also guarantee that references to the initialized
- // object do not occur before the load of the initialization flag.
//
- // In LLVM, we do this by marking the load Acquire.
- if (threadsafe)
- LI->setAtomic(llvm::AtomicOrdering::Acquire);
+ // If threadsafe statics are enabled, but we don't have inline atomics, just
+ // call __cxa_guard_acquire unconditionally. The "inline" check isn't
+ // actually inline, and the user might not expect calls to __atomic libcalls.
- // For ARM, we should only check the first bit, rather than the entire byte:
- //
- // ARM C++ ABI 3.2.3.1:
- // To support the potential use of initialization guard variables
- // as semaphores that are the target of ARM SWP and LDREX/STREX
- // synchronizing instructions we define a static initialization
- // guard variable to be a 4-byte aligned, 4-byte word with the
- // following inline access protocol.
- // #define INITIALIZED 1
- // if ((obj_guard & INITIALIZED) != INITIALIZED) {
- // if (__cxa_guard_acquire(&obj_guard))
- // ...
- // }
- //
- // and similarly for ARM64:
- //
- // ARM64 C++ ABI 3.2.2:
- // This ABI instead only specifies the value bit 0 of the static guard
- // variable; all other bits are platform defined. Bit 0 shall be 0 when the
- // variable is not initialized and 1 when it is.
- llvm::Value *V =
- (UseARMGuardVarABI && !useInt8GuardVariable)
- ? Builder.CreateAnd(LI, llvm::ConstantInt::get(CGM.Int8Ty, 1))
- : LI;
- llvm::Value *NeedsInit = Builder.CreateIsNull(V, "guard.uninitialized");
-
- llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
+ unsigned MaxInlineWidthInBits = CGF.getTarget().getMaxAtomicInlineWidth();
llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
-
- // Check if the first byte of the guard variable is zero.
- CGF.EmitCXXGuardedInitBranch(NeedsInit, InitCheckBlock, EndBlock,
- CodeGenFunction::GuardKind::VariableGuard, &D);
-
- CGF.EmitBlock(InitCheckBlock);
+ if (!threadsafe || MaxInlineWidthInBits) {
+ // Load the first byte of the guard variable.
+ llvm::LoadInst *LI =
+ Builder.CreateLoad(Builder.CreateElementBitCast(guardAddr, CGM.Int8Ty));
+
+ // Itanium ABI:
+ // An implementation supporting thread-safety on multiprocessor
+ // systems must also guarantee that references to the initialized
+ // object do not occur before the load of the initialization flag.
+ //
+ // In LLVM, we do this by marking the load Acquire.
+ if (threadsafe)
+ LI->setAtomic(llvm::AtomicOrdering::Acquire);
+
+ // For ARM, we should only check the first bit, rather than the entire byte:
+ //
+ // ARM C++ ABI 3.2.3.1:
+ // To support the potential use of initialization guard variables
+ // as semaphores that are the target of ARM SWP and LDREX/STREX
+ // synchronizing instructions we define a static initialization
+ // guard variable to be a 4-byte aligned, 4-byte word with the
+ // following inline access protocol.
+ // #define INITIALIZED 1
+ // if ((obj_guard & INITIALIZED) != INITIALIZED) {
+ // if (__cxa_guard_acquire(&obj_guard))
+ // ...
+ // }
+ //
+ // and similarly for ARM64:
+ //
+ // ARM64 C++ ABI 3.2.2:
+ // This ABI instead only specifies the value bit 0 of the static guard
+ // variable; all other bits are platform defined. Bit 0 shall be 0 when the
+ // variable is not initialized and 1 when it is.
+ llvm::Value *V =
+ (UseARMGuardVarABI && !useInt8GuardVariable)
+ ? Builder.CreateAnd(LI, llvm::ConstantInt::get(CGM.Int8Ty, 1))
+ : LI;
+ llvm::Value *NeedsInit = Builder.CreateIsNull(V, "guard.uninitialized");
+
+ llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
+
+ // Check if the first byte of the guard variable is zero.
+ CGF.EmitCXXGuardedInitBranch(NeedsInit, InitCheckBlock, EndBlock,
+ CodeGenFunction::GuardKind::VariableGuard, &D);
+
+ CGF.EmitBlock(InitCheckBlock);
+ }
// Variables used when coping with thread-safe statics and exceptions.
if (threadsafe) {
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