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update maxIntAlignment for x86 to 16

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LLVMABIAlignmentOfType(i128) reports 16 on this target, however the C
ABI uses align(4).

Clang in LLVM 17 does this:

%struct.foo = type { i32, i128 }

Clang in LLVM 18 does this:

%struct.foo = type <{ i32, i128 }>

Clang is working around the 16-byte alignment to use align(4) for the C
ABI by making the LLVM struct packed.
This commit is contained in:
Andrew Kelley 2024-04-30 19:51:35 -07:00
parent 927f24a6ff
commit 200e06b239
2 changed files with 2 additions and 43 deletions
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6
src/type.zig
View file

@ -1572,11 +1572,6 @@ pub const Type = struct {
.wasm64, .wasm64,
=> 8, => 8,
.x86 => if (target.ofmt == .c) 16 else return switch (target.os.tag) {
.windows, .uefi => 8,
else => 4,
},
// For these, LLVMABIAlignmentOfType(i128) reports 8. Note that 16 // For these, LLVMABIAlignmentOfType(i128) reports 8. Note that 16
// is a relevant number in three cases: // is a relevant number in three cases:
// 1. Different machine code instruction when loading into SIMD register. // 1. Different machine code instruction when loading into SIMD register.
@ -1599,6 +1594,7 @@ pub const Type = struct {
}, },
// Even LLVMABIAlignmentOfType(i128) agrees on these targets. // Even LLVMABIAlignmentOfType(i128) agrees on these targets.
.x86,
.aarch64, .aarch64,
.aarch64_be, .aarch64_be,
.aarch64_32, .aarch64_32,

39
test/behavior/align.zig
View file

@ -114,44 +114,6 @@ test "alignment and size of structs with 128-bit fields" {
.u129_size = 24, .u129_size = 24,
}, },
.x86 => if (builtin.object_format == .c) .{
.a_align = 16,
.a_size = 16,
.b_align = 16,
.b_size = 32,
.u128_align = 16,
.u128_size = 16,
.u129_align = 16,
.u129_size = 32,
} else switch (builtin.os.tag) {
.windows => .{
.a_align = 8,
.a_size = 16,
.b_align = 16,
.b_size = 32,
.u128_align = 8,
.u128_size = 16,
.u129_align = 8,
.u129_size = 24,
},
else => .{
.a_align = 4,
.a_size = 16,
.b_align = 16,
.b_size = 32,
.u128_align = 4,
.u128_size = 16,
.u129_align = 4,
.u129_size = 20,
},
},
.mips64, .mips64,
.mips64el, .mips64el,
.powerpc64, .powerpc64,
@ -211,6 +173,7 @@ test "alignment and size of structs with 128-bit fields" {
}, },
}, },
.x86,
.aarch64, .aarch64,
.aarch64_be, .aarch64_be,
.aarch64_32, .aarch64_32,