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[Bitfield] Add an option to access bitfield in a fine-grained manner.
Currently all the consecutive bitfields are wrapped as a large integer unless there is unamed zero sized bitfield in between. The patch provides an alternative manner which makes the bitfield to be accessed as separate memory location if it has legal integer width and is naturally aligned. Such separate bitfield may split the original consecutive bitfields into subgroups of consecutive bitfields, and each subgroup will be wrapped as an integer. Now This is all controlled by an option -ffine-grained-bitfield-accesses. The alternative of bitfield access manner can improve the access efficiency of those bitfields with legal width and being aligned, but may reduce the chance of load/store combining of other bitfields, so it depends on how the bitfields are defined and actually accessed to choose when to use the option. For now the option is off by default. Differential revision: https://reviews.llvm.org/D36562 llvm-svn: 315915
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,162 @@ | ||
| // RUN: %clang_cc1 -triple x86_64-linux-gnu -ffine-grained-bitfield-accesses \ | ||
| // RUN: -emit-llvm -o - %s | FileCheck %s | ||
| // RUN: %clang_cc1 -triple x86_64-linux-gnu -ffine-grained-bitfield-accesses \ | ||
| // RUN: -emit-llvm -fsanitize=address -o - %s | FileCheck %s --check-prefix=SANITIZE | ||
| // Check -fsplit-bitfields will be ignored since sanitizer is enabled. | ||
|
|
||
| struct S1 { | ||
| unsigned f1:2; | ||
| unsigned f2:6; | ||
| unsigned f3:8; | ||
| unsigned f4:4; | ||
| unsigned f5:8; | ||
| }; | ||
|
|
||
| S1 a1; | ||
| unsigned read8_1() { | ||
| // CHECK-LABEL: @_Z7read8_1v | ||
| // CHECK: %bf.load = load i8, i8* getelementptr inbounds (%struct.S1, %struct.S1* @a1, i32 0, i32 1), align 1 | ||
| // CHECK-NEXT: %bf.cast = zext i8 %bf.load to i32 | ||
| // CHECK-NEXT: ret i32 %bf.cast | ||
| // SANITIZE-LABEL: @_Z7read8_1v | ||
| // SANITIZE: %bf.load = load i32, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE: %bf.lshr = lshr i32 %bf.load, 8 | ||
| // SANITIZE: %bf.clear = and i32 %bf.lshr, 255 | ||
| // SANITIZE: ret i32 %bf.clear | ||
| return a1.f3; | ||
| } | ||
| void write8_1() { | ||
| // CHECK-LABEL: @_Z8write8_1v | ||
| // CHECK: store i8 3, i8* getelementptr inbounds (%struct.S1, %struct.S1* @a1, i32 0, i32 1), align 1 | ||
| // CHECK-NEXT: ret void | ||
| // SANITIZE-LABEL: @_Z8write8_1v | ||
| // SANITIZE: %bf.load = load i32, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE-NEXT: %bf.clear = and i32 %bf.load, -65281 | ||
| // SANITIZE-NEXT: %bf.set = or i32 %bf.clear, 768 | ||
| // SANITIZE-NEXT: store i32 %bf.set, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE-NEXT: ret void | ||
| a1.f3 = 3; | ||
| } | ||
|
|
||
| unsigned read8_2() { | ||
| // CHECK-LABEL: @_Z7read8_2v | ||
| // CHECK: %bf.load = load i16, i16* getelementptr inbounds (%struct.S1, %struct.S1* @a1, i32 0, i32 2), align 2 | ||
| // CHECK-NEXT: %bf.lshr = lshr i16 %bf.load, 4 | ||
| // CHECK-NEXT: %bf.clear = and i16 %bf.lshr, 255 | ||
| // CHECK-NEXT: %bf.cast = zext i16 %bf.clear to i32 | ||
| // CHECK-NEXT: ret i32 %bf.cast | ||
| // SANITIZE-LABEL: @_Z7read8_2v | ||
| // SANITIZE: %bf.load = load i32, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE-NEXT: %bf.lshr = lshr i32 %bf.load, 20 | ||
| // SANITIZE-NEXT: %bf.clear = and i32 %bf.lshr, 255 | ||
| // SANITIZE-NEXT: ret i32 %bf.clear | ||
| return a1.f5; | ||
| } | ||
| void write8_2() { | ||
| // CHECK-LABEL: @_Z8write8_2v | ||
| // CHECK: %bf.load = load i16, i16* getelementptr inbounds (%struct.S1, %struct.S1* @a1, i32 0, i32 2), align 2 | ||
| // CHECK-NEXT: %bf.clear = and i16 %bf.load, -4081 | ||
| // CHECK-NEXT: %bf.set = or i16 %bf.clear, 48 | ||
| // CHECK-NEXT: store i16 %bf.set, i16* getelementptr inbounds (%struct.S1, %struct.S1* @a1, i32 0, i32 2), align 2 | ||
| // CHECK-NEXT: ret void | ||
| // SANITIZE-LABEL: @_Z8write8_2v | ||
| // SANITIZE: %bf.load = load i32, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE-NEXT: %bf.clear = and i32 %bf.load, -267386881 | ||
| // SANITIZE-NEXT: %bf.set = or i32 %bf.clear, 3145728 | ||
| // SANITIZE-NEXT: store i32 %bf.set, i32* getelementptr inbounds {{.*}}, align 4 | ||
| // SANITIZE-NEXT: ret void | ||
| a1.f5 = 3; | ||
| } | ||
|
|
||
| struct S2 { | ||
| unsigned long f1:16; | ||
| unsigned long f2:16; | ||
| unsigned long f3:6; | ||
| }; | ||
|
|
||
| S2 a2; | ||
| unsigned read16_1() { | ||
| // CHECK-LABEL: @_Z8read16_1v | ||
| // CHECK: %bf.load = load i16, i16* getelementptr inbounds (%struct.S2, %struct.S2* @a2, i32 0, i32 0), align 8 | ||
| // CHECK-NEXT: %bf.cast = zext i16 %bf.load to i64 | ||
| // CHECK-NEXT: %conv = trunc i64 %bf.cast to i32 | ||
| // CHECK-NEXT: ret i32 %conv | ||
| // SANITIZE-LABEL: @_Z8read16_1v | ||
| // SANITIZE: %bf.load = load i64, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.clear = and i64 %bf.load, 65535 | ||
| // SANITIZE-NEXT: %conv = trunc i64 %bf.clear to i32 | ||
| // SANITIZE-NEXT: ret i32 %conv | ||
| return a2.f1; | ||
| } | ||
| unsigned read16_2() { | ||
| // CHECK-LABEL: @_Z8read16_2v | ||
| // CHECK: %bf.load = load i16, i16* getelementptr inbounds (%struct.S2, %struct.S2* @a2, i32 0, i32 1), align 2 | ||
| // CHECK-NEXT: %bf.cast = zext i16 %bf.load to i64 | ||
| // CHECK-NEXT: %conv = trunc i64 %bf.cast to i32 | ||
| // CHECK-NEXT: ret i32 %conv | ||
| // SANITIZE-LABEL: @_Z8read16_2v | ||
| // SANITIZE: %bf.load = load i64, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.lshr = lshr i64 %bf.load, 16 | ||
| // SANITIZE-NEXT: %bf.clear = and i64 %bf.lshr, 65535 | ||
| // SANITIZE-NEXT: %conv = trunc i64 %bf.clear to i32 | ||
| // SANITIZE-NEXT: ret i32 %conv | ||
| return a2.f2; | ||
| } | ||
|
|
||
| void write16_1() { | ||
| // CHECK-LABEL: @_Z9write16_1v | ||
| // CHECK: store i16 5, i16* getelementptr inbounds (%struct.S2, %struct.S2* @a2, i32 0, i32 0), align 8 | ||
| // CHECK-NEXT: ret void | ||
| // SANITIZE-LABEL: @_Z9write16_1v | ||
| // SANITIZE: %bf.load = load i64, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.clear = and i64 %bf.load, -65536 | ||
| // SANITIZE-NEXT: %bf.set = or i64 %bf.clear, 5 | ||
| // SANITIZE-NEXT: store i64 %bf.set, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: ret void | ||
| a2.f1 = 5; | ||
| } | ||
| void write16_2() { | ||
| // CHECK-LABEL: @_Z9write16_2v | ||
| // CHECK: store i16 5, i16* getelementptr inbounds (%struct.S2, %struct.S2* @a2, i32 0, i32 1), align 2 | ||
| // CHECK-NEXT: ret void | ||
| // SANITIZE-LABEL: @_Z9write16_2v | ||
| // SANITIZE: %bf.load = load i64, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.clear = and i64 %bf.load, -4294901761 | ||
| // SANITIZE-NEXT: %bf.set = or i64 %bf.clear, 327680 | ||
| // SANITIZE-NEXT: store i64 %bf.set, i64* bitcast {{.*}}, align 8 | ||
| // SANITIZE-NEXT: ret void | ||
| a2.f2 = 5; | ||
| } | ||
|
|
||
| struct S3 { | ||
| unsigned long f1:14; | ||
| unsigned long f2:18; | ||
| unsigned long f3:32; | ||
| }; | ||
|
|
||
| S3 a3; | ||
| unsigned read32_1() { | ||
| // CHECK-LABEL: @_Z8read32_1v | ||
| // CHECK: %bf.load = load i32, i32* getelementptr inbounds (%struct.S3, %struct.S3* @a3, i32 0, i32 1), align 4 | ||
| // CHECK-NEXT: %bf.cast = zext i32 %bf.load to i64 | ||
| // CHECK-NEXT: %conv = trunc i64 %bf.cast to i32 | ||
| // CHECK-NEXT: ret i32 %conv | ||
| // SANITIZE-LABEL: @_Z8read32_1v | ||
| // SANITIZE: %bf.load = load i64, i64* getelementptr inbounds {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.lshr = lshr i64 %bf.load, 32 | ||
| // SANITIZE-NEXT: %conv = trunc i64 %bf.lshr to i32 | ||
| // SANITIZE-NEXT: ret i32 %conv | ||
| return a3.f3; | ||
| } | ||
| void write32_1() { | ||
| // CHECK-LABEL: @_Z9write32_1v | ||
| // CHECK: store i32 5, i32* getelementptr inbounds (%struct.S3, %struct.S3* @a3, i32 0, i32 1), align 4 | ||
| // CHECK-NEXT: ret void | ||
| // SANITIZE-LABEL: @_Z9write32_1v | ||
| // SANITIZE: %bf.load = load i64, i64* getelementptr inbounds {{.*}}, align 8 | ||
| // SANITIZE-NEXT: %bf.clear = and i64 %bf.load, 4294967295 | ||
| // SANITIZE-NEXT: %bf.set = or i64 %bf.clear, 21474836480 | ||
| // SANITIZE-NEXT: store i64 %bf.set, i64* getelementptr inbounds {{.*}}, align 8 | ||
| // SANITIZE-NEXT: ret void | ||
| a3.f3 = 5; | ||
| } |