Index: include/clang/Basic/LangOptions.def =================================================================== --- include/clang/Basic/LangOptions.def +++ include/clang/Basic/LangOptions.def @@ -156,6 +156,7 @@ "default struct packing maximum alignment") VALUE_LANGOPT(MaxTypeAlign , 32, 0, "default maximum alignment for types") +VALUE_LANGOPT(AlignDouble , 1, 0, "Controls if doubles should be aligned to 8 bytes (x86 only)") COMPATIBLE_VALUE_LANGOPT(PICLevel , 2, 0, "__PIC__ level") COMPATIBLE_VALUE_LANGOPT(PIELevel , 2, 0, "__PIE__ level") COMPATIBLE_LANGOPT(GNUInline , 1, 0, "GNU inline semantics") Index: include/clang/Driver/Options.td =================================================================== --- include/clang/Driver/Options.td +++ include/clang/Driver/Options.td @@ -1320,6 +1320,8 @@ def mieee_fp : Flag<["-"], "mieee-fp">, Group; def minline_all_stringops : Flag<["-"], "minline-all-stringops">, Group; def mno_inline_all_stringops : Flag<["-"], "mno-inline-all-stringops">, Group; +def malign_double : Flag<["-"], "malign-double">, Group, Flags<[CC1Option]>, + HelpText<"Align doubles to two words in structs (x86 only)">; def mfloat_abi_EQ : Joined<["-"], "mfloat-abi=">, Group; def mfpmath_EQ : Joined<["-"], "mfpmath=">, Group; def mfpu_EQ : Joined<["-"], "mfpu=">, Group; Index: lib/Basic/TargetInfo.cpp =================================================================== --- lib/Basic/TargetInfo.cpp +++ lib/Basic/TargetInfo.cpp @@ -275,6 +275,10 @@ UseBitFieldTypeAlignment = false; if (Opts.ShortWChar) WCharType = UnsignedShort; + if (Opts.AlignDouble) { + DoubleAlign = LongLongAlign = 64; + LongDoubleAlign = 64; + } if (Opts.OpenCL) { // OpenCL C requires specific widths for types, irrespective of Index: lib/Frontend/CompilerInvocation.cpp =================================================================== --- lib/Frontend/CompilerInvocation.cpp +++ lib/Frontend/CompilerInvocation.cpp @@ -1758,6 +1758,7 @@ Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls); Opts.PackStruct = getLastArgIntValue(Args, OPT_fpack_struct_EQ, 0, Diags); Opts.MaxTypeAlign = getLastArgIntValue(Args, OPT_fmax_type_align_EQ, 0, Diags); + Opts.AlignDouble = Args.hasArg(OPT_malign_double); Opts.PICLevel = getLastArgIntValue(Args, OPT_pic_level, 0, Diags); Opts.PIELevel = getLastArgIntValue(Args, OPT_pie_level, 0, Diags); Opts.Static = Args.hasArg(OPT_static_define); Index: test/CodeGen/malign-double.cpp =================================================================== --- /dev/null +++ test/CodeGen/malign-double.cpp @@ -0,0 +1,115 @@ +// RUN: %clang_cc1 -malign-double -triple i386-unknown-linux -emit-llvm %s -o - \ +// RUN: | FileCheck --check-prefix=CHECK-ON --check-prefix=CHECK %s + +// RUN: %clang_cc1 -triple i386-unknown-linux -emit-llvm %s -o - \ +// RUN: | FileCheck --check-prefix=CHECK-OFF --check-prefix=CHECK %s + +/* Structs S1, S2, S3, S4, and union U5 are taken from Intel, "IA-64 + Software Conventions and Runtime Architecture Guide", version of + August 1999, Section 4.2, Figures 4-1 through 4-5. + A Union containing a double was also thrown in for good measure. */ + +struct S1 { + char c; +}; + +unsigned S1_align = __alignof(struct S1); +unsigned S1_size = sizeof(struct S1); +// CHECK: @S1_align = global i32 1, align 4 +// CHECK: @S1_size = global i32 1, align 4 + +unsigned S1_c_offset = (unsigned) &((struct S1*) 0)->c; +// CHECK: @S1_c_offset = global i32 0, align 4 + +struct S2{ + char c; + char d; + short s; + int n; +}; + +unsigned S2_align = __alignof(struct S2); +unsigned S2_size = sizeof(struct S2); +// CHECK: @S2_align = global i32 4, align 4 +// CHECK: @S2_size = global i32 8, align 4 + +unsigned S2_c_offset = (unsigned) &((struct S2*) 0)->c; +unsigned S2_d_offset = (unsigned) &((struct S2*) 0)->d; +unsigned S2_s_offset = (unsigned) &((struct S2*) 0)->s; +unsigned S2_n_offset = (unsigned) &((struct S2*) 0)->n; +// CHECK: @S2_c_offset = global i32 0, align 4 +// CHECK: @S2_d_offset = global i32 1, align 4 +// CHECK: @S2_s_offset = global i32 2, align 4 +// CHECK: @S2_n_offset = global i32 4, align 4 + +struct S3 { + char c; + short s; +}; + +unsigned S3_align = __alignof(struct S3); +unsigned S3_size = sizeof(struct S3); +// CHECK: @S3_align = global i32 2, align 4 +// CHECK: @S3_size = global i32 4, align 4 + +unsigned S3_c_offset = (unsigned) &((struct S3*) 0)->c; +unsigned S3_s_offset = (unsigned) &((struct S3*) 0)->s; +// CHECK: @S3_c_offset = global i32 0, align 4 +// CHECK: @S3_s_offset = global i32 2, align 4 + +struct S4 { + char c; + double d; + short s; +}; + +unsigned S4_align = __alignof(struct S4); +unsigned S4_size = sizeof(struct S4); +// CHECK-ON: @S4_align = global i32 8, align 4 +// CHECK-ON: @S4_size = global i32 24, align 4 +// CHECK-OFF: @S4_align = global i32 4, align 4 +// CHECK-OFF: @S4_size = global i32 16, align 4 + +unsigned S4_c_offset = (unsigned) &((struct S4*) 0)->c; +unsigned S4_d_offset = (unsigned) &((struct S4*) 0)->d; +unsigned S4_s_offset = (unsigned) &((struct S4*) 0)->s; +// CHECK: @S4_c_offset = global i32 0, align 4 +// CHECK-ON: @S4_d_offset = global i32 8, align 4 +// CHECK-ON: @S4_s_offset = global i32 16, align 4 +// CHECK-OFF: @S4_d_offset = global i32 4, align 4 +// CHECK-OFF: @S4_s_offset = global i32 12, align 4 + +union S5 { + char c; + short s; + int j; +}; + +unsigned S5_align = __alignof(union S5); +unsigned S5_size = sizeof(union S5); +// CHECK: @S5_align = global i32 4, align 4 +// CHECK: @S5_size = global i32 4, align 4 + +unsigned S5_c_offset = (unsigned) &((union S5*) 0)->c; +unsigned S5_s_offset = (unsigned) &((union S5*) 0)->s; +unsigned S5_j_offset = (unsigned) &((union S5*) 0)->j; +// CHECK: @S5_c_offset = global i32 0, align 4 +// CHECK: @S5_s_offset = global i32 0, align 4 +// CHECK: @S5_j_offset = global i32 0, align 4 + +union S6 { + char c; + double d; +}; + +unsigned S6_align = __alignof(union S6); +unsigned S6_size = sizeof(union S6); +// CHECK-ON: @S6_align = global i32 8, align 4 +// CHECK-ON: @S6_size = global i32 8, align 4 +// CHECK-OFF: @S6_align = global i32 4, align 4 +// CHECK-OFF: @S6_size = global i32 8, align 4 + +unsigned S6_c_offset = (unsigned) &((union S6*) 0)->c; +unsigned S6_d_offset = (unsigned) &((union S6*) 0)->d; +// CHECK: @S6_c_offset = global i32 0, align 4 +// CHECK: @S6_d_offset = global i32 0, align 4