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Add more ARM helpers to compiler runtime #25542

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ce2223f
Add more ARM helpers to compiler runtime
sindrom91 Oct 10, 2025
1ab0e35
Disable __aeabi_cdcmpxx tests for Thumb and PAC
sindrom91 Oct 13, 2025
0254255
Use the same CPSR struct for LE and BE
sindrom91 Oct 13, 2025
19b16ff
Resolve endianess at compile time.
sindrom91 Oct 27, 2025
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195 changes: 195 additions & 0 deletions lib/compiler_rt/cmpdf2.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,20 @@
const common = @import("./common.zig");
const comparef = @import("./comparef.zig");

const std = @import("std");
const builtin = @import("builtin");

pub const panic = common.panic;

comptime {
if (common.want_aeabi) {
@export(&__aeabi_dcmpeq, .{ .name = "__aeabi_dcmpeq", .linkage = common.linkage, .visibility = common.visibility });
@export(&__aeabi_dcmplt, .{ .name = "__aeabi_dcmplt", .linkage = common.linkage, .visibility = common.visibility });
@export(&__aeabi_dcmple, .{ .name = "__aeabi_dcmple", .linkage = common.linkage, .visibility = common.visibility });
if (builtin.cpu.arch.isArm() and !builtin.cpu.arch.isThumb() and !builtin.cpu.has(.arm, .pacbti)) {
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@alexrp alexrp Oct 27, 2025

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Why these conditions?

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@sindrom91 sindrom91 Oct 27, 2025

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In LLVM, Thumb and PAC implementation details are behind flags and different macros (this, this, this, this). I assume this implementation wouldn't work for Thumb and PAC.

@export(&__aeabi_cdcmple, .{ .name = "__aeabi_cdcmple", .linkage = common.linkage, .visibility = common.visibility });
@export(&__aeabi_cdcmpeq, .{ .name = "__aeabi_cdcmpeq", .linkage = common.linkage, .visibility = common.visibility });
}
} else {
@export(&__eqdf2, .{ .name = "__eqdf2", .linkage = common.linkage, .visibility = common.visibility });
@export(&__nedf2, .{ .name = "__nedf2", .linkage = common.linkage, .visibility = common.visibility });
Expand Down Expand Up @@ -66,3 +73,191 @@ fn __aeabi_dcmplt(a: f64, b: f64) callconv(.{ .arm_aapcs = .{} }) i32 {
fn __aeabi_dcmple(a: f64, b: f64) callconv(.{ .arm_aapcs = .{} }) i32 {
return @intFromBool(comparef.cmpf2(f64, comparef.LE, a, b) != .Greater);
}

fn __aeabi_cdcmpeq_check_nan(a: f64, b: f64) callconv(.c) i32 {
return @intFromBool(std.math.isNan(a) or std.math.isNan(b));
}

// This function compares two doubles and returns the result in CPSR register.
//
// C code equivalent:
//
// void __aeabi_cdcmpeq(double a, double b) {
// if (isnan(a) || isnan(b)) {
// Z = 0; C = 1;
// } else {
// __aeabi_cdcmple(a, b);
// }
// }
//
// Code has been taken from LLVM implementation:
// https://github.com/llvm/llvm-project/blob/7eee67202378932d03331ad04e7d07ed4d988381/compiler-rt/lib/builtins/arm/aeabi_cdcmp.S
//
fn __aeabi_cdcmpeq(_: f64, _: f64) callconv(.naked) void {
const apsr_c = 0x20000000;
asm volatile (
\\ push {r0-r3, lr}
\\ bl %[__aeabi_cdcmpeq_check_nan]
\\ cmp r0, #1
\\ pop {r0-r3, lr}
\\ bne %[__aeabi_cdcmple]
\\ msr APSR_nzcvq, %[APSR_C]
\\ bx lr
:
: [__aeabi_cdcmple] "X" (&__aeabi_cdcmple),
[__aeabi_cdcmpeq_check_nan] "X" (&__aeabi_cdcmpeq_check_nan),
[APSR_C] "i" (apsr_c),
);
}

// This function compares two doubles and returns the result in CPSR register.
//
// C code equivalent:
//
// void __aeabi_cdcmple(double a, double b) {
// if (__aeabi_dcmplt(a, b)) {
// Z = 0; C = 0;
// } else if (__aeabi_dcmpeq(a, b)) {
// Z = 1; C = 1;
// } else {
// Z = 0; C = 1;
// }
// }
//
// Code has been taken from LLVM implementation:
// https://github.com/llvm/llvm-project/blob/7eee67202378932d03331ad04e7d07ed4d988381/compiler-rt/lib/builtins/arm/aeabi_cdcmp.S
//
fn __aeabi_cdcmple(_: f64, _: f64) callconv(.naked) void {
const apsr_c = 0x20000000;
const apsr_z = 0x40000000;
asm volatile (
\\ push {r0-r3, lr}
\\ bl %[__aeabi_dcmplt]
\\ cmp r0, #1
\\ moveq ip, #0
\\ beq 1f
\\ ldm sp, {r0-r3}
\\ bl %[__aeabi_dcmpeq]
\\ cmp r0, #1
\\ moveq ip, %[APSR_CZ]
\\ movne ip, %[APSR_C]
\\1:
\\ msr APSR_nzcvq, ip
\\ pop {r0-r3}
\\ pop {pc}
:
: [__aeabi_dcmplt] "X" (&__aeabi_dcmplt),
[__aeabi_dcmpeq] "X" (&__aeabi_dcmpeq),
[APSR_C] "i" (apsr_c),
[APSR_CZ] "i" (apsr_c | apsr_z),
);
}

const CPSRFlags = packed struct {
filler: u28,
v: u1,
c: u1,
z: u1,
n: u1,
};

const CPSR = packed union {
flags: CPSRFlags,
value: u32,
};

const __aeabi_cdcmpxx = *const fn (f64, f64) callconv(.naked) void;

fn call__aeabi_cdcmpxx(comptime func: __aeabi_cdcmpxx, a: f64, b: f64) CPSR {
const A: u64 = @bitCast(a);
const B: u64 = @bitCast(b);

const le = comptime builtin.cpu.arch.endian() == .little;
const a_lo: u32 = if (le) @truncate(A) else @truncate(A >> 32);
const a_hi: u32 = if (le) @truncate(A >> 32) else @truncate(A);
const b_lo: u32 = if (le) @truncate(B) else @truncate(B >> 32);
const b_hi: u32 = if (le) @truncate(B >> 32) else @truncate(B);

const result = asm volatile (
\\ bl %[func]
\\ mrs %[out], apsr
: [out] "=r" (-> u32),
: [r0] "{r0}" (a_lo),
[r1] "{r1}" (a_hi),
[r2] "{r2}" (b_lo),
[r3] "{r3}" (b_hi),
[func] "X" (func),
);
return .{ .value = result };
}

// This test has been copied from LLVM:
// https://github.com/llvm/llvm-project/blob/7eee67202378932d03331ad04e7d07ed4d988381/compiler-rt/test/builtins/Unit/arm/aeabi_cdcmpeq_test.c
//
test "test __aeabi_cdcmpeq" {
if (!builtin.cpu.arch.isArm() or builtin.cpu.arch.isThumb() or builtin.cpu.has(.arm, .pacbti)) return error.SkipZigTest;

const t = std.testing;
const nan = std.math.nan(f64);
const inf = std.math.inf(f64);

try t.expectEqual(@as(u1, 1), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 1.0, 1.0).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 1234.567, 765.4321).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, -123.0, -678.0).flags.z);
try t.expectEqual(@as(u1, 1), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 0.0, -0.0).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 1.0, nan).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, nan, 1.0).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, nan, nan).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, inf, 1.0).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 0.0, inf).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, -inf, 0.0).flags.z);
try t.expectEqual(@as(u1, 0), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, 0.0, -inf).flags.z);
try t.expectEqual(@as(u1, 1), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, inf, inf).flags.z);
try t.expectEqual(@as(u1, 1), call__aeabi_cdcmpxx(&__aeabi_cdcmpeq, -inf, -inf).flags.z);
}

// This test has been copied from LLVM:
// https://github.com/llvm/llvm-project/blob/7eee67202378932d03331ad04e7d07ed4d988381/compiler-rt/test/builtins/Unit/arm/aeabi_cdcmple_test.c
//
test "test __aeabi_cdcmple" {
if (!builtin.cpu.arch.isArm() or builtin.cpu.arch.isThumb() or builtin.cpu.has(.arm, .pacbti)) return error.SkipZigTest;

const t = std.testing;
const nan = std.math.nan(f64);

var cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, 1.0, 1.0);
try t.expectEqual(@as(u1, 1), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, 1234.567, 765.4321);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, 765.4321, 1234.567);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 0), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, -123.0, -678.0);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, -678.0, -123.0);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 0), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, 0.0, -0.0);
try t.expectEqual(@as(u1, 1), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, 1.0, nan);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, nan, 1.0);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);

cpsr = call__aeabi_cdcmpxx(&__aeabi_cdcmple, nan, nan);
try t.expectEqual(@as(u1, 0), cpsr.flags.z);
try t.expectEqual(@as(u1, 1), cpsr.flags.c);
}