tschuett created this revision.
tschuett added a reviewer: rsmith.
Herald added a reviewer: jfb.
Herald added subscribers: cfe-commits, jfb.
Herald added a project: clang.
tschuett requested review of this revision.
Herald added a subscriber: dexonsmith.
"Listing the alignment and access size (== expected alignment) in the warning
seems like a good idea."
solves PR 46947
struct Foo {
struct Bar {
void * a;
void * b;
};
Bar bar;
};
struct ThirtyTwo {
struct Large {
void * a;
void * b;
void * c;
void * d;
};
Large bar;
};
void braz(Foo *foo, ThirtyTwo *braz) {
Foo::Bar bar;
__atomic_load(&foo->bar, &bar, __ATOMIC_RELAXED);
ThirtyTwo::Large foobar;
__atomic_load(&braz->bar, &foobar, __ATOMIC_RELAXED);
}
repro.cpp:21:3: warning: misaligned atomic operation may incur significant
performance penalty (the expected (16 bytes) exceeds the actual alignment (8
bytes) [-Watomic-alignment]
__atomic_load(&foo->bar, &bar, __ATOMIC_RELAXED);
^
repro.cpp:24:3: warning: misaligned atomic operation may incur significant
performance penalty (the expected (32 bytes) exceeds the actual alignment (8
bytes) [-Watomic-alignment]
__atomic_load(&braz->bar, &foobar, __ATOMIC_RELAXED);
^
repro.cpp:24:3: warning: large atomic operation may incur significant
performance penalty (the access size (32 bytes) exceeds the max lock-free size
(16 bytes)) [-Watomic-alignment]
3 warnings generated.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D85102
Files:
clang/include/clang/Basic/DiagnosticFrontendKinds.td
clang/include/clang/Basic/DiagnosticGroups.td
clang/lib/CodeGen/CGAtomic.cpp
Index: clang/lib/CodeGen/CGAtomic.cpp
===================================================================
--- clang/lib/CodeGen/CGAtomic.cpp
+++ clang/lib/CodeGen/CGAtomic.cpp
@@ -807,10 +807,20 @@
bool Oversized = getContext().toBits(sizeChars) > MaxInlineWidthInBits;
bool Misaligned = (Ptr.getAlignment() % sizeChars) != 0;
bool UseLibcall = Misaligned | Oversized;
+ CharUnits MaxInlineWidth =
+ getContext().toCharUnitsFromBits(MaxInlineWidthInBits);
- if (UseLibcall) {
- CGM.getDiags().Report(E->getBeginLoc(), diag::warn_atomic_op_misaligned)
- << !Oversized;
+ DiagnosticsEngine &Diags = CGM.getDiags();
+
+ if (Misaligned) {
+ Diags.Report(E->getBeginLoc(), diag::warn_atomic_op_misaligned)
+ << (int)sizeChars.getQuantity()
+ << (int)Ptr.getAlignment().getQuantity();
+ }
+
+ if (Oversized) {
+ Diags.Report(E->getBeginLoc(), diag::warn_atomic_op_oversized)
+ << (int)sizeChars.getQuantity() << (int)MaxInlineWidth.getQuantity();
}
llvm::Value *Order = EmitScalarExpr(E->getOrder());
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -699,6 +699,7 @@
def Reorder : DiagGroup<"reorder", [ReorderCtor, ReorderInitList]>;
def UndeclaredSelector : DiagGroup<"undeclared-selector">;
def ImplicitAtomic : DiagGroup<"implicit-atomic-properties">;
+def AtomicAlignment : DiagGroup<"atomic-alignment">;
def CustomAtomic : DiagGroup<"custom-atomic-properties">;
def AtomicProperties : DiagGroup<"atomic-properties",
[ImplicitAtomic, CustomAtomic]>;
Index: clang/include/clang/Basic/DiagnosticFrontendKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -270,8 +270,16 @@
"ifunc resolver function must return a pointer">;
def warn_atomic_op_misaligned : Warning<
- "%select{large|misaligned}0 atomic operation may incur "
- "significant performance penalty">, InGroup<DiagGroup<"atomic-alignment">>;
+ "misaligned atomic operation may incur "
+ "significant performance penalty "
+ "(the expected (%0 bytes) exceeds the actual alignment (%1 bytes)">,
+ InGroup<AtomicAlignment>;
+
+def warn_atomic_op_oversized : Warning<
+ "large atomic operation may incur "
+ "significant performance penalty "
+ "(the access size (%0 bytes) exceeds the max lock-free size (%1 bytes))">,
+InGroup<AtomicAlignment>;
def warn_alias_with_section : Warning<
"%select{alias|ifunc}1 will not be in section '%0' but in the same section "
Index: clang/lib/CodeGen/CGAtomic.cpp
===================================================================
--- clang/lib/CodeGen/CGAtomic.cpp
+++ clang/lib/CodeGen/CGAtomic.cpp
@@ -807,10 +807,20 @@
bool Oversized = getContext().toBits(sizeChars) > MaxInlineWidthInBits;
bool Misaligned = (Ptr.getAlignment() % sizeChars) != 0;
bool UseLibcall = Misaligned | Oversized;
+ CharUnits MaxInlineWidth =
+ getContext().toCharUnitsFromBits(MaxInlineWidthInBits);
- if (UseLibcall) {
- CGM.getDiags().Report(E->getBeginLoc(), diag::warn_atomic_op_misaligned)
- << !Oversized;
+ DiagnosticsEngine &Diags = CGM.getDiags();
+
+ if (Misaligned) {
+ Diags.Report(E->getBeginLoc(), diag::warn_atomic_op_misaligned)
+ << (int)sizeChars.getQuantity()
+ << (int)Ptr.getAlignment().getQuantity();
+ }
+
+ if (Oversized) {
+ Diags.Report(E->getBeginLoc(), diag::warn_atomic_op_oversized)
+ << (int)sizeChars.getQuantity() << (int)MaxInlineWidth.getQuantity();
}
llvm::Value *Order = EmitScalarExpr(E->getOrder());
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -699,6 +699,7 @@
def Reorder : DiagGroup<"reorder", [ReorderCtor, ReorderInitList]>;
def UndeclaredSelector : DiagGroup<"undeclared-selector">;
def ImplicitAtomic : DiagGroup<"implicit-atomic-properties">;
+def AtomicAlignment : DiagGroup<"atomic-alignment">;
def CustomAtomic : DiagGroup<"custom-atomic-properties">;
def AtomicProperties : DiagGroup<"atomic-properties",
[ImplicitAtomic, CustomAtomic]>;
Index: clang/include/clang/Basic/DiagnosticFrontendKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -270,8 +270,16 @@
"ifunc resolver function must return a pointer">;
def warn_atomic_op_misaligned : Warning<
- "%select{large|misaligned}0 atomic operation may incur "
- "significant performance penalty">, InGroup<DiagGroup<"atomic-alignment">>;
+ "misaligned atomic operation may incur "
+ "significant performance penalty "
+ "(the expected (%0 bytes) exceeds the actual alignment (%1 bytes)">,
+ InGroup<AtomicAlignment>;
+
+def warn_atomic_op_oversized : Warning<
+ "large atomic operation may incur "
+ "significant performance penalty "
+ "(the access size (%0 bytes) exceeds the max lock-free size (%1 bytes))">,
+InGroup<AtomicAlignment>;
def warn_alias_with_section : Warning<
"%select{alias|ifunc}1 will not be in section '%0' but in the same section "
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