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Diffstat (limited to 'clang/test/CodeGenCXX/bitfield.cpp')
| -rw-r--r-- | clang/test/CodeGenCXX/bitfield.cpp | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/clang/test/CodeGenCXX/bitfield.cpp b/clang/test/CodeGenCXX/bitfield.cpp new file mode 100644 index 00000000000..a737304c98d --- /dev/null +++ b/clang/test/CodeGenCXX/bitfield.cpp @@ -0,0 +1,195 @@ +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -verify -emit-llvm -o - %s | FileCheck %s +// +// Tests for bitfield access patterns in C++ with special attention to +// conformance to C++11 memory model requirements. + +namespace N1 { + // Ensure that neither loads nor stores to bitfields are not widened into + // other memory locations. (PR13691) + // + // NOTE: We could potentially widen loads based on their alignment if we are + // comfortable requiring that subsequent memory locations within the + // alignment-widened load are not volatile. + struct S { + char a; + unsigned b : 1; + char c; + }; + unsigned read(S* s) { + // CHECK: define i32 @_ZN2N14read + // CHECK: %[[ptr:.*]] = getelementptr inbounds %{{.*}}* %{{.*}}, i32 0, i32 1 + // CHECK: %[[val:.*]] = load i8* %[[ptr]] + // CHECK: %[[and:.*]] = and i8 %[[val]], 1 + // CHECK: %[[ext:.*]] = zext i8 %[[and]] to i32 + // CHECK: ret i32 %[[ext]] + return s->b; + } + void write(S* s, unsigned x) { + // CHECK: define void @_ZN2N15write + // CHECK: %[[ptr:.*]] = getelementptr inbounds %{{.*}}* %{{.*}}, i32 0, i32 1 + // CHECK: %[[x_trunc:.*]] = trunc i32 %{{.*}} to i8 + // CHECK: %[[old:.*]] = load i8* %[[ptr]] + // CHECK: %[[x_and:.*]] = and i8 %[[x_trunc]], 1 + // CHECK: %[[old_and:.*]] = and i8 %[[old]], -2 + // CHECK: %[[new:.*]] = or i8 %[[old_and]], %[[x_and]] + // CHECK: store i8 %[[new]], i8* %[[ptr]] + s->b = x; + } +} + +namespace N2 { + // Do widen loads and stores to bitfields when those bitfields have padding + // within the struct following them. + struct S { + unsigned b : 24; + void *p; + }; + unsigned read(S* s) { + // CHECK: define i32 @_ZN2N24read + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[val:.*]] = load i32* %[[ptr]] + // CHECK: %[[and:.*]] = and i32 %[[val]], 16777215 + // CHECK: ret i32 %[[and]] + return s->b; + } + void write(S* s, unsigned x) { + // CHECK: define void @_ZN2N25write + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[old:.*]] = load i32* %[[ptr]] + // CHECK: %[[x_and:.*]] = and i32 %{{.*}}, 16777215 + // CHECK: %[[old_and:.*]] = and i32 %[[old]], -16777216 + // CHECK: %[[new:.*]] = or i32 %[[old_and]], %[[x_and]] + // CHECK: store i32 %[[new]], i32* %[[ptr]] + s->b = x; + } +} + +namespace N3 { + // Do widen loads and stores to bitfields through the trailing padding at the + // end of a struct. + struct S { + unsigned b : 24; + }; + unsigned read(S* s) { + // CHECK: define i32 @_ZN2N34read + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[val:.*]] = load i32* %[[ptr]] + // CHECK: %[[and:.*]] = and i32 %[[val]], 16777215 + // CHECK: ret i32 %[[and]] + return s->b; + } + void write(S* s, unsigned x) { + // CHECK: define void @_ZN2N35write + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[old:.*]] = load i32* %[[ptr]] + // CHECK: %[[x_and:.*]] = and i32 %{{.*}}, 16777215 + // CHECK: %[[old_and:.*]] = and i32 %[[old]], -16777216 + // CHECK: %[[new:.*]] = or i32 %[[old_and]], %[[x_and]] + // CHECK: store i32 %[[new]], i32* %[[ptr]] + s->b = x; + } +} + +namespace N4 { + // Do NOT widen loads and stores to bitfields into padding at the end of + // a class which might end up with members inside of it when inside a derived + // class. + struct Base { + virtual ~Base() {} + + unsigned b : 24; + }; + // Imagine some other translation unit introduces: +#if 0 + struct Derived : public Base { + char c; + }; +#endif + unsigned read(Base* s) { + // FIXME: We should widen this load as long as the function isn't being + // instrumented by thread-sanitizer. + // + // CHECK: define i32 @_ZN2N44read + // CHECK: %[[ptr:.*]] = bitcast {{.*}}* %{{.*}} to i24* + // CHECK: %[[val:.*]] = load i24* %[[ptr]] + // CHECK: %[[ext:.*]] = zext i24 %[[val]] to i32 + // CHECK: ret i32 %[[ext]] + return s->b; + } + void write(Base* s, unsigned x) { + // CHECK: define void @_ZN2N45write + // CHECK: %[[ptr:.*]] = bitcast {{.*}}* %{{.*}} to i24* + // CHECK: %[[new:.*]] = trunc i32 %{{.*}} to i24 + // CHECK: store i24 %[[new]], i24* %[[ptr]] + s->b = x; + } +} + +namespace N5 { + // Widen through padding at the end of a struct even if that struct + // participates in a union with another struct which has a separate field in + // that location. The reasoning is that if the operation is storing to that + // member of the union, it must be the active member, and thus we can write + // through the padding. If it is a load, it might be a load of a common + // prefix through a non-active member, but in such a case the extra bits + // loaded are masked off anyways. + union U { + struct X { unsigned b : 24; char c; } x; + struct Y { unsigned b : 24; } y; + }; + unsigned read(U* u) { + // CHECK: define i32 @_ZN2N54read + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[val:.*]] = load i32* %[[ptr]] + // CHECK: %[[and:.*]] = and i32 %[[val]], 16777215 + // CHECK: ret i32 %[[and]] + return u->y.b; + } + void write(U* u, unsigned x) { + // CHECK: define void @_ZN2N55write + // CHECK: %[[ptr:.*]] = bitcast %{{.*}}* %{{.*}} to i32* + // CHECK: %[[old:.*]] = load i32* %[[ptr]] + // CHECK: %[[x_and:.*]] = and i32 %{{.*}}, 16777215 + // CHECK: %[[old_and:.*]] = and i32 %[[old]], -16777216 + // CHECK: %[[new:.*]] = or i32 %[[old_and]], %[[x_and]] + // CHECK: store i32 %[[new]], i32* %[[ptr]] + u->y.b = x; + } +} + +namespace N6 { + // Zero-length bitfields partition the memory locations of bitfields for the + // purposes of the memory model. That means stores must not span zero-length + // bitfields and loads may only span them when we are not instrumenting with + // thread sanitizer. + // FIXME: We currently don't widen loads even without thread sanitizer, even + // though we could. + struct S { + unsigned b1 : 24; + unsigned char : 0; + unsigned char b2 : 8; + }; + unsigned read(S* s) { + // CHECK: define i32 @_ZN2N64read + // CHECK: %[[ptr1:.*]] = bitcast {{.*}}* %{{.*}} to i24* + // CHECK: %[[val1:.*]] = load i24* %[[ptr1]] + // CHECK: %[[ext1:.*]] = zext i24 %[[val1]] to i32 + // CHECK: %[[ptr2:.*]] = getelementptr inbounds {{.*}}* %{{.*}}, i32 0, i32 1 + // CHECK: %[[val2:.*]] = load i8* %[[ptr2]] + // CHECK: %[[ext2:.*]] = zext i8 %[[val2]] to i32 + // CHECK: %[[add:.*]] = add nsw i32 %[[ext1]], %[[ext2]] + // CHECK: ret i32 %[[add]] + return s->b1 + s->b2; + } + void write(S* s, unsigned x) { + // CHECK: define void @_ZN2N65write + // CHECK: %[[ptr1:.*]] = bitcast {{.*}}* %{{.*}} to i24* + // CHECK: %[[new1:.*]] = trunc i32 %{{.*}} to i24 + // CHECK: store i24 %[[new1]], i24* %[[ptr1]] + // CHECK: %[[new2:.*]] = trunc i32 %{{.*}} to i8 + // CHECK: %[[ptr2:.*]] = getelementptr inbounds {{.*}}* %{{.*}}, i32 0, i32 1 + // CHECK: store i8 %[[new2]], i8* %[[ptr2]] + s->b1 = x; + s->b2 = x; + } +} |
