[clang] e18c6ef - [clang] improve diagnostics for misaligned and large atomics
JF Bastien via cfe-commits
cfe-commits at lists.llvm.org
Tue Aug 4 11:10:42 PDT 2020
Author: Thorsten Schuett
Date: 2020-08-04T11:10:29-07:00
New Revision: e18c6ef6b41a59af73bf5c3d7d52a8c53a471e5d
URL: https://github.com/llvm/llvm-project/commit/e18c6ef6b41a59af73bf5c3d7d52a8c53a471e5d
DIFF: https://github.com/llvm/llvm-project/commit/e18c6ef6b41a59af73bf5c3d7d52a8c53a471e5d.diff
LOG: [clang] improve diagnostics for misaligned and large atomics
"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.
Differential Revision: https://reviews.llvm.org/D85102
Added:
Modified:
clang/include/clang/Basic/DiagnosticFrontendKinds.td
clang/include/clang/Basic/DiagnosticGroups.td
clang/lib/CodeGen/CGAtomic.cpp
clang/test/CodeGen/atomics-sema-alignment.c
Removed:
################################################################################
diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
index b202d2abffa0..6434d92fd8fc 100644
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -270,8 +270,16 @@ def err_ifunc_resolver_return : Error<
"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 alignment (%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 "
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 1e829be4028e..be62461faef4 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -699,6 +699,7 @@ def ReorderInitList : DiagGroup<"reorder-init-list">;
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]>;
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index a58450ddd4c5..b7ada4ac7e3b 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -807,10 +807,20 @@ RValue CodeGenFunction::EmitAtomicExpr(AtomicExpr *E) {
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());
diff --git a/clang/test/CodeGen/atomics-sema-alignment.c b/clang/test/CodeGen/atomics-sema-alignment.c
index 9443af354ec5..d0058f1da8b0 100644
--- a/clang/test/CodeGen/atomics-sema-alignment.c
+++ b/clang/test/CodeGen/atomics-sema-alignment.c
@@ -12,10 +12,10 @@ typedef int __attribute__((aligned(1))) unaligned_int;
void func(IntPair *p) {
IntPair res;
- __atomic_load(p, &res, 0); // expected-warning {{misaligned atomic operation may incur significant performance penalty}}
- __atomic_store(p, &res, 0); // expected-warning {{misaligned atomic operation may incur significant performance penalty}}
- __atomic_fetch_add((unaligned_int *)p, 1, 2); // expected-warning {{misaligned atomic operation may incur significant performance penalty}}
- __atomic_fetch_sub((unaligned_int *)p, 1, 3); // expected-warning {{misaligned atomic operation may incur significant performance penalty}}
+ __atomic_load(p, &res, 0); // expected-warning {{misaligned atomic operation may incur significant performance penalty; the expected alignment (8 bytes) exceeds the actual alignment (4 bytes)}}
+ __atomic_store(p, &res, 0); // expected-warning {{misaligned atomic operation may incur significant performance penalty; the expected alignment (8 bytes) exceeds the actual alignment (4 bytes)}}
+ __atomic_fetch_add((unaligned_int *)p, 1, 2); // expected-warning {{misaligned atomic operation may incur significant performance penalty; the expected alignment (4 bytes) exceeds the actual alignment (1 bytes)}}
+ __atomic_fetch_sub((unaligned_int *)p, 1, 3); // expected-warning {{misaligned atomic operation may incur significant performance penalty; the expected alignment (4 bytes) exceeds the actual alignment (1 bytes)}}
}
void func1(LongStruct *p) {
@@ -25,3 +25,24 @@ void func1(LongStruct *p) {
__atomic_fetch_add((int *)p, 1, 2);
__atomic_fetch_sub((int *)p, 1, 3);
}
+
+typedef struct {
+ void *a;
+ void *b;
+} Foo;
+
+typedef struct {
+ void *a;
+ void *b;
+ void *c;
+ void *d;
+} __attribute__((aligned(32))) ThirtyTwo;
+
+void braz(Foo *foo, ThirtyTwo *braz) {
+ Foo bar;
+ __atomic_load(foo, &bar, __ATOMIC_RELAXED); // expected-warning {{misaligned atomic operation may incur significant performance penalty; the expected alignment (16 bytes) exceeds the actual alignment (8 bytes)}}
+
+ ThirtyTwo thirtyTwo1;
+ ThirtyTwo thirtyTwo2;
+ __atomic_load(&thirtyTwo1, &thirtyTwo2, __ATOMIC_RELAXED); // expected-warning {{large atomic operation may incur significant performance penalty; the access size (32 bytes) exceeds the max lock-free size (16 bytes)}}
+}
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