This revision was automatically updated to reflect the committed changes.
thegameg marked an inline comment as done.
Closed by commit rG143f6b837790: [IRGen] Emit lifetime markers for temporary
struct allocas (authored by thegameg).
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Repository:
rG LLVM Github Monorepo
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https://reviews.llvm.org/D68611/new/
https://reviews.llvm.org/D68611
Files:
clang/lib/CodeGen/CGCall.cpp
clang/test/CodeGen/aarch64-byval-temp.c
Index: clang/test/CodeGen/aarch64-byval-temp.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/aarch64-byval-temp.c
@@ -0,0 +1,89 @@
+// RUN: %clang_cc1 -emit-llvm -triple arm64-- -o - %s -O0 | FileCheck %s --check-prefix=CHECK-O0
+// RUN: %clang_cc1 -emit-llvm -disable-llvm-optzns -triple arm64-- -o - %s -O3 | FileCheck %s --check-prefix=CHECK-O3
+
+struct large {
+ void* pointers[8];
+};
+
+void pass_large(struct large);
+
+// For arm64, we don't use byval to pass structs but instead we create
+// temporary allocas.
+//
+// Make sure we generate the appropriate lifetime markers for the temporary
+// allocas so that the optimizer can re-use stack slots if possible.
+void example() {
+ struct large l = {0};
+ pass_large(l);
+ pass_large(l);
+}
+// CHECK-O0-LABEL: define void @example(
+// The alloca for the struct on the stack.
+// CHECK-O0: %[[l:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+// The alloca for the temporary stack space that we use to pass the argument.
+// CHECK-O0-NEXT: %[[byvaltemp:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+// Another one to pass the argument to the second function call.
+// CHECK-O0-NEXT: %[[byvaltemp1:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+// First, memset `l` to 0.
+// CHECK-O0-NEXT: %[[bitcastl:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O0-NEXT: call void @llvm.memset.p0i8.i64(i8* align 8 %[[bitcastl]], i8 0, i64 64, i1 false)
+// Then, memcpy `l` to the temporary stack space.
+// CHECK-O0-NEXT: %[[src:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp]] to i8*
+// CHECK-O0-NEXT: %[[dst:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O0-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 %[[src]], i8* align 8 %[[dst]], i64 64, i1 false)
+// Finally, call using a pointer to the temporary stack space.
+// CHECK-O0-NEXT: call void @pass_large(%struct.large* %[[byvaltemp]])
+// Now, do the same for the second call, using the second temporary alloca.
+// CHECK-O0-NEXT: %[[src:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp1]] to i8*
+// CHECK-O0-NEXT: %[[dst:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O0-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 %[[src]], i8* align 8 %[[dst]], i64 64, i1 false)
+// CHECK-O0-NEXT: call void @pass_large(%struct.large* %[[byvaltemp1]])
+// CHECK-O0-NEXT: ret void
+//
+// At O3, we should have lifetime markers to help the optimizer re-use the temporary allocas.
+//
+// CHECK-O3-LABEL: define void @example(
+// The alloca for the struct on the stack.
+// CHECK-O3: %[[l:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+// The alloca for the temporary stack space that we use to pass the argument.
+// CHECK-O3-NEXT: %[[byvaltemp:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+// Another one to pass the argument to the second function call.
+// CHECK-O3-NEXT: %[[byvaltemp1:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
+//
+// Mark the start of the lifetime for `l`
+// CHECK-O3-NEXT: %[[bitcastl:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0i8(i64 64, i8* %[[bitcastl]])
+//
+// First, memset `l` to 0.
+// CHECK-O3-NEXT: %[[bitcastl:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O3-NEXT: call void @llvm.memset.p0i8.i64(i8* align 8 %[[bitcastl]], i8 0, i64 64, i1 false)
+//
+// Lifetime of the first temporary starts here and ends right after the call.
+// CHECK-O3-NEXT: %[[bitcastbyvaltemp:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp]] to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0i8(i64 64, i8* %[[bitcastbyvaltemp]])
+//
+// Then, memcpy `l` to the temporary stack space.
+// CHECK-O3-NEXT: %[[src:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp]] to i8*
+// CHECK-O3-NEXT: %[[dst:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O3-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 %[[src]], i8* align 8 %[[dst]], i64 64, i1 false)
+// Finally, call using a pointer to the temporary stack space.
+// CHECK-O3-NEXT: call void @pass_large(%struct.large* %[[byvaltemp]])
+//
+// The lifetime of the temporary used to pass a pointer to the struct ends here.
+// CHECK-O3-NEXT: %[[bitcastbyvaltemp:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp]] to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0i8(i64 64, i8* %[[bitcastbyvaltemp]])
+//
+// Now, do the same for the second call, using the second temporary alloca.
+// CHECK-O3-NEXT: %[[bitcastbyvaltemp:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp1]] to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0i8(i64 64, i8* %[[bitcastbyvaltemp]])
+// CHECK-O3-NEXT: %[[src:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp1]] to i8*
+// CHECK-O3-NEXT: %[[dst:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[l]] to i8*
+// CHECK-O3-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 %[[src]], i8* align 8 %[[dst]], i64 64, i1 false)
+// CHECK-O3-NEXT: call void @pass_large(%struct.large* %[[byvaltemp1]])
+// CHECK-O3-NEXT: %[[bitcastbyvaltemp:[0-9A-Za-z-]+]] = bitcast %struct.large* %[[byvaltemp1]] to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0i8(i64 64, i8* %[[bitcastbyvaltemp]])
+//
+// Mark the end of the lifetime of `l`.
+// CHECK-O3-NEXT: %[[bitcastl:[0-9A-Za-z-]+]] = bitcast %struct.large* %l to i8*
+// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0i8(i64 64, i8* %[[bitcastl]])
+// CHECK-O3-NEXT: ret void
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -3878,6 +3878,11 @@
Address swiftErrorTemp = Address::invalid();
Address swiftErrorArg = Address::invalid();
+ // When passing arguments using temporary allocas, we need to add the
+ // appropriate lifetime markers. This vector keeps track of all the lifetime
+ // markers that need to be ended right after the call.
+ SmallVector<CallLifetimeEnd, 2> CallLifetimeEndAfterCall;
+
// Translate all of the arguments as necessary to match the IR lowering.
assert(CallInfo.arg_size() == CallArgs.size() &&
"Mismatch between function signature & arguments.");
@@ -3994,6 +3999,18 @@
Address AI = CreateMemTempWithoutCast(
I->Ty, ArgInfo.getIndirectAlign(), "byval-temp");
IRCallArgs[FirstIRArg] = AI.getPointer();
+
+ // Emit lifetime markers for the temporary alloca.
+ uint64_t ByvalTempElementSize =
+ CGM.getDataLayout().getTypeAllocSize(AI.getElementType());
+ llvm::Value *LifetimeSize =
+ EmitLifetimeStart(ByvalTempElementSize, AI.getPointer());
+
+ // Add cleanup code to emit the end lifetime marker after the call.
+ if (LifetimeSize) // In case we disabled lifetime markers.
+ CallLifetimeEndAfterCall.emplace_back(AI, LifetimeSize);
+
+ // Generate the copy.
I->copyInto(*this, AI);
} else {
// Skip the extra memcpy call.
@@ -4562,6 +4579,11 @@
}
}
+ // Explicitly call CallLifetimeEnd::Emit just to re-use the code even though
+ // we can't use the full cleanup mechanism.
+ for (CallLifetimeEnd &LifetimeEnd : CallLifetimeEndAfterCall)
+ LifetimeEnd.Emit(*this, /*Flags=*/{});
+
return Ret;
}
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