From 952becc0bdf814f194a42d34ea78fed792a1f760 Mon Sep 17 00:00:00 2001 From: beetrees Date: Tue, 2 Apr 2024 05:08:56 +0100 Subject: [PATCH] Ensure floats are returned losslessly by the Rust ABI on 32-bit x86 --- compiler/rustc_ty_utils/src/abi.rs | 34 ++ tests/assembly/x86-return-float.rs | 323 ++++++++++++++++++ .../ui/abi/numbers-arithmetic/return-float.rs | 57 ++++ 3 files changed, 414 insertions(+) create mode 100644 tests/assembly/x86-return-float.rs create mode 100644 tests/ui/abi/numbers-arithmetic/return-float.rs diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs index c5ea85c90dc5d..ca503dd16b998 100644 --- a/compiler/rustc_ty_utils/src/abi.rs +++ b/compiler/rustc_ty_utils/src/abi.rs @@ -744,6 +744,40 @@ fn fn_abi_adjust_for_abi<'tcx>( return; } + // Avoid returning floats in x87 registers on x86 as loading and storing from x87 + // registers will quiet signalling NaNs. + if cx.tcx.sess.target.arch == "x86" + && arg_idx.is_none() + // Intrinsics themselves are not actual "real" functions, so theres no need to + // change their ABIs. + && abi != SpecAbi::RustIntrinsic + { + match arg.layout.abi { + // Handle similar to the way arguments with an `Abi::Aggregate` abi are handled + // below, by returning arguments up to the size of a pointer (32 bits on x86) + // cast to an appropriately sized integer. + Abi::Scalar(s) if s.primitive() == Float(F32) => { + // Same size as a pointer, return in a register. + arg.cast_to(Reg::i32()); + return; + } + Abi::Scalar(s) if s.primitive() == Float(F64) => { + // Larger than a pointer, return indirectly. + arg.make_indirect(); + return; + } + Abi::ScalarPair(s1, s2) + if matches!(s1.primitive(), Float(F32 | F64)) + || matches!(s2.primitive(), Float(F32 | F64)) => + { + // Larger than a pointer, return indirectly. + arg.make_indirect(); + return; + } + _ => {} + }; + } + match arg.layout.abi { Abi::Aggregate { .. } => {} diff --git a/tests/assembly/x86-return-float.rs b/tests/assembly/x86-return-float.rs new file mode 100644 index 0000000000000..270aea2475f00 --- /dev/null +++ b/tests/assembly/x86-return-float.rs @@ -0,0 +1,323 @@ +//@ assembly-output: emit-asm +//@ only-x86 +// Force frame pointers to make ASM more consistent between targets +//@ compile-flags: -O -C force-frame-pointers +//@ filecheck-flags: --implicit-check-not fld --implicit-check-not fst +//@ revisions: unix windows +//@[unix] ignore-windows +//@[windows] only-windows + +#![crate_type = "lib"] +#![feature(f16, f128)] + +// Tests that returning `f32` and `f64` with the "Rust" ABI on 32-bit x86 doesn't use the x87 +// floating point stack, as loading and storing `f32`s and `f64`s to and from the x87 stack quietens +// signalling NaNs. + +// Returning individual floats + +// CHECK-LABEL: return_f32: +#[no_mangle] +pub fn return_f32(x: f32) -> f32 { + // CHECK: movl {{.*}}(%ebp), %eax + // CHECK-NOT: ax + // CHECK: retl + x +} + +// CHECK-LABEL: return_f64: +#[no_mangle] +pub fn return_f64(x: f64) -> f64 { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL:.*]] + // CHECK-NEXT: movsd %[[VAL]], (%[[PTR]]) + // CHECK: retl + x +} + +// Returning scalar pairs containing floats + +// CHECK-LABEL: return_f32_f32: +#[no_mangle] +pub fn return_f32_f32(x: (f32, f32)) -> (f32, f32) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 4(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_f64_f64: +#[no_mangle] +pub fn return_f64_f64(x: (f64, f64)) -> (f64, f64) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+12]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movsd %[[VAL2]], 8(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_f32_f64: +#[no_mangle] +pub fn return_f32_f64(x: (f32, f64)) -> (f32, f64) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movsd %[[VAL2]], {{4|8}}(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_f64_f32: +#[no_mangle] +pub fn return_f64_f32(x: (f64, f32)) -> (f64, f32) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+12]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 8(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_f32_other: +#[no_mangle] +pub fn return_f32_other(x: (f32, usize)) -> (f32, usize) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movl %[[VAL2]], 4(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_f64_other: +#[no_mangle] +pub fn return_f64_other(x: (f64, usize)) -> (f64, usize) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+12]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movl %[[VAL2]], 8(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_other_f32: +#[no_mangle] +pub fn return_other_f32(x: (usize, f32)) -> (usize, f32) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movl %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 4(%[[PTR]]) + // CHECK: retl + x +} + +// CHECK-LABEL: return_other_f64: +#[no_mangle] +pub fn return_other_f64(x: (usize, f64)) -> (usize, f64) { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movsd [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movl %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movsd %[[VAL2]], {{4|8}}(%[[PTR]]) + // CHECK: retl + x +} + +// Calling functions returning floats + +// CHECK-LABEL: call_f32: +#[no_mangle] +pub unsafe fn call_f32(x: &mut f32) { + extern "Rust" { + fn get_f32() -> f32; + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f32 + // CHECK-NEXT: movl %eax, (%[[PTR]]) + *x = get_f32(); +} + +// CHECK-LABEL: call_f64: +#[no_mangle] +pub unsafe fn call_f64(x: &mut f64) { + extern "Rust" { + fn get_f64() -> f64; + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f64 + // CHECK: movsd {{.*}}(%{{ebp|esp}}), %[[VAL:.*]] + // CHECK-NEXT: movsd %[[VAL:.*]], (%[[PTR]]) + *x = get_f64(); +} + +// Calling functions returning scalar pairs containing floats + +// CHECK-LABEL: call_f32_f32: +#[no_mangle] +pub unsafe fn call_f32_f32(x: &mut (f32, f32)) { + extern "Rust" { + fn get_f32_f32() -> (f32, f32); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f32_f32 + // CHECK: movss [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+4]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 4(%[[PTR]]) + *x = get_f32_f32(); +} + +// CHECK-LABEL: call_f64_f64: +#[no_mangle] +pub unsafe fn call_f64_f64(x: &mut (f64, f64)) { + extern "Rust" { + fn get_f64_f64() -> (f64, f64); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f64_f64 + // unix: movsd [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // unix-NEXT: movsd [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // windows: movsd (%esp), %[[VAL1:.*]] + // windows-NEXT: movsd 8(%esp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movsd %[[VAL2]], 8(%[[PTR]]) + *x = get_f64_f64(); +} + +// CHECK-LABEL: call_f32_f64: +#[no_mangle] +pub unsafe fn call_f32_f64(x: &mut (f32, f64)) { + extern "Rust" { + fn get_f32_f64() -> (f32, f64); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f32_f64 + // unix: movss [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // unix-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL2:.*]] + // windows: movss (%esp), %[[VAL1:.*]] + // windows-NEXT: movsd 8(%esp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // unix-NEXT: movsd %[[VAL2]], 4(%[[PTR]]) + // windows-NEXT: movsd %[[VAL2]], 8(%[[PTR]]) + *x = get_f32_f64(); +} + +// CHECK-LABEL: call_f64_f32: +#[no_mangle] +pub unsafe fn call_f64_f32(x: &mut (f64, f32)) { + extern "Rust" { + fn get_f64_f32() -> (f64, f32); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f64_f32 + // unix: movsd [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // unix-NEXT: movss [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // windows: movsd (%esp), %[[VAL1:.*]] + // windows-NEXT: movss 8(%esp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 8(%[[PTR]]) + *x = get_f64_f32(); +} + +// CHECK-LABEL: call_f32_other: +#[no_mangle] +pub unsafe fn call_f32_other(x: &mut (f32, usize)) { + extern "Rust" { + fn get_f32_other() -> (f32, usize); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f32_other + // CHECK: movss [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+4]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movss %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movl %[[VAL2]], 4(%[[PTR]]) + *x = get_f32_other(); +} + +// CHECK-LABEL: call_f64_other: +#[no_mangle] +pub unsafe fn call_f64_other(x: &mut (f64, usize)) { + extern "Rust" { + fn get_f64_other() -> (f64, usize); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_f64_other + // unix: movsd [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // unix-NEXT: movl [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // windows: movsd (%esp), %[[VAL1:.*]] + // windows-NEXT: movl 8(%esp), %[[VAL2:.*]] + // CHECK-NEXT: movsd %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movl %[[VAL2]], 8(%[[PTR]]) + *x = get_f64_other(); +} + +// CHECK-LABEL: call_other_f32: +#[no_mangle] +pub unsafe fn call_other_f32(x: &mut (usize, f32)) { + extern "Rust" { + fn get_other_f32() -> (usize, f32); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_other_f32 + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movss [[#%d,OFFSET+4]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movl %[[VAL1]], (%[[PTR]]) + // CHECK-NEXT: movss %[[VAL2]], 4(%[[PTR]]) + *x = get_other_f32(); +} + +// CHECK-LABEL: call_other_f64: +#[no_mangle] +pub unsafe fn call_other_f64(x: &mut (usize, f64)) { + extern "Rust" { + fn get_other_f64() -> (usize, f64); + } + // CHECK: movl {{.*}}(%ebp), %[[PTR:.*]] + // CHECK: calll {{()|_}}get_other_f64 + // unix: movl [[#%d,OFFSET:]](%ebp), %[[VAL1:.*]] + // unix-NEXT: movsd [[#%d,OFFSET+4]](%ebp), %[[VAL2:.*]] + // windows: movl (%esp), %[[VAL1:.*]] + // windows-NEXT: movsd 8(%esp), %[[VAL2:.*]] + // CHECK-NEXT: movl %[[VAL1]], (%[[PTR]]) + // unix-NEXT: movsd %[[VAL2]], 4(%[[PTR]]) + // windows-NEXT: movsd %[[VAL2]], 8(%[[PTR]]) + *x = get_other_f64(); +} + +// The "C" ABI for `f16` and `f128` on x86 has never used the x87 floating point stack. Do some +// basic checks to ensure this remains the case for the "Rust" ABI. + +// CHECK-LABEL: return_f16: +#[no_mangle] +pub fn return_f16(x: f16) -> f16 { + // CHECK: pinsrw $0, {{.*}}(%ebp), %xmm0 + // CHECK-NOT: xmm0 + // CHECK: retl + x +} + +// CHECK-LABEL: return_f128: +#[no_mangle] +pub fn return_f128(x: f128) -> f128 { + // CHECK: movl [[#%d,OFFSET:]](%ebp), %[[PTR:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+16]](%ebp), %[[VAL4:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+4]](%ebp), %[[VAL1:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+8]](%ebp), %[[VAL2:.*]] + // CHECK-NEXT: movl [[#%d,OFFSET+12]](%ebp), %[[VAL3:.*]] + // CHECK-NEXT: movl %[[VAL4:.*]] 12(%[[PTR]]) + // CHECK-NEXT: movl %[[VAL3:.*]] 8(%[[PTR]]) + // CHECK-NEXT: movl %[[VAL2:.*]] 4(%[[PTR]]) + // CHECK-NEXT: movl %[[VAL1:.*]] (%[[PTR]]) + // CHECK: retl + x +} diff --git a/tests/ui/abi/numbers-arithmetic/return-float.rs b/tests/ui/abi/numbers-arithmetic/return-float.rs new file mode 100644 index 0000000000000..3b025b763f138 --- /dev/null +++ b/tests/ui/abi/numbers-arithmetic/return-float.rs @@ -0,0 +1,57 @@ +//@ run-pass +//@ compile-flags: -Copt-level=0 + +// Test that floats (in particular signalling NaNs) are losslessly returned from functions. + +fn main() { + let bits_f32 = std::hint::black_box([ + 4.2_f32.to_bits(), + f32::INFINITY.to_bits(), + f32::NEG_INFINITY.to_bits(), + f32::NAN.to_bits(), + // These two masks cover all the mantissa bits. One of them is a signalling NaN, the other + // is quiet. + // Similar to the masks in `test_float_bits_conv` in library/std/src/f32/tests.rs + f32::NAN.to_bits() ^ 0x002A_AAAA, + f32::NAN.to_bits() ^ 0x0055_5555, + // Same as above but with the sign bit flipped. + f32::NAN.to_bits() ^ 0x802A_AAAA, + f32::NAN.to_bits() ^ 0x8055_5555, + ]); + for bits in bits_f32 { + assert_eq!(identity(f32::from_bits(bits)).to_bits(), bits); + // Test types that are returned as scalar pairs. + assert_eq!(identity((f32::from_bits(bits), 42)).0.to_bits(), bits); + assert_eq!(identity((42, f32::from_bits(bits))).1.to_bits(), bits); + let (a, b) = identity((f32::from_bits(bits), f32::from_bits(bits))); + assert_eq!((a.to_bits(), b.to_bits()), (bits, bits)); + } + + let bits_f64 = std::hint::black_box([ + 4.2_f64.to_bits(), + f64::INFINITY.to_bits(), + f64::NEG_INFINITY.to_bits(), + f64::NAN.to_bits(), + // These two masks cover all the mantissa bits. One of them is a signalling NaN, the other + // is quiet. + // Similar to the masks in `test_float_bits_conv` in library/std/src/f64/tests.rs + f64::NAN.to_bits() ^ 0x000A_AAAA_AAAA_AAAA, + f64::NAN.to_bits() ^ 0x0005_5555_5555_5555, + // Same as above but with the sign bit flipped. + f64::NAN.to_bits() ^ 0x800A_AAAA_AAAA_AAAA, + f64::NAN.to_bits() ^ 0x8005_5555_5555_5555, + ]); + for bits in bits_f64 { + assert_eq!(identity(f64::from_bits(bits)).to_bits(), bits); + // Test types that are returned as scalar pairs. + assert_eq!(identity((f64::from_bits(bits), 42)).0.to_bits(), bits); + assert_eq!(identity((42, f64::from_bits(bits))).1.to_bits(), bits); + let (a, b) = identity((f64::from_bits(bits), f64::from_bits(bits))); + assert_eq!((a.to_bits(), b.to_bits()), (bits, bits)); + } +} + +#[inline(never)] +fn identity(x: T) -> T { + x +}