Auto merge of rust-lang#131871 - RalfJung:x86-32-float, r=workingjubilee

x86-32 float return for 'Rust' ABI: treat all float types consistently This helps with rust-lang#131819: for our own ABI on x86-32, we want to *never* use the float registers. The previous logic only considered F32 and F64, but skipped F16 and F128. So I made the logic just apply to all float types.
rust-lang-ci · Oct 22, 2024 · 8b863d7 · 8b863d7
2 parents 814df6e + 57d5f86
commit 8b863d7
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Showing 3 changed files with 46 additions and 46 deletions.
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
@@ -1,6 +1,5 @@
 use std::iter;
 
-use rustc_abi::Float::*;
 use rustc_abi::Primitive::{Float, Pointer};
 use rustc_abi::{Abi, AddressSpace, PointerKind, Scalar, Size};
 use rustc_hir as hir;
@@ -695,37 +694,31 @@ fn fn_abi_adjust_for_abi<'tcx>(
  }
 
  // Avoid returning floats in x87 registers on x86 as loading and storing from x87
- // registers will quiet signalling NaNs.
+ // registers will quiet signalling NaNs. Also avoid using SSE registers since they
+ // are not always available (depending on target features).
  if 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;
+ let has_float = match arg.layout.abi {
+ Abi::Scalar(s) => matches!(s.primitive(), Float(_)),
+ Abi::ScalarPair(s1, s2) => {
+ matches!(s1.primitive(), Float(_)) || matches!(s2.primitive(), Float(_))
  }
- 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)) =>
- {
+ _ => false, // anyway not passed via registers on x86
+ };
+ if has_float {
+ if arg.layout.size <= Pointer(AddressSpace::DATA).size(cx) {
+ // Same size or smaller than pointer, return in a register.
+ arg.cast_to(Reg { kind: RegKind::Integer, size: arg.layout.size });
+ } else {
  // Larger than a pointer, return indirectly.
  arg.make_indirect();
- return;
  }
- _ => {}
- };
+ return;
+ }
  }
 
  if arg_idx.is_none() && arg.layout.size > Pointer(AddressSpace::DATA).size(cx) * 2 {

diff --git a/tests/codegen/float/f128.rs b/tests/codegen/float/f128.rs
@@ -1,4 +1,4 @@
-// 32-bit x86 returns `f32` and `f64` differently to avoid the x87 stack.
+// 32-bit x86 returns float types differently to avoid the x87 stack.
 // 32-bit systems will return 128bit values using a return area pointer.
 //@ revisions: x86 bit32 bit64
 //@[x86] only-x86
@@ -152,7 +152,9 @@ pub fn f128_rem_assign(a: &mut f128, b: f128) {
 
 /* float to float conversions */
 
-// CHECK-LABEL: half @f128_as_f16(
+// x86-LABEL: i16 @f128_as_f16(
+// bits32-LABEL: half @f128_as_f16(
+// bits64-LABEL: half @f128_as_f16(
 #[no_mangle]
 pub fn f128_as_f16(a: f128) -> f16 {
  // CHECK: fptrunc fp128 %{{.+}} to half

diff --git a/tests/codegen/float/f16.rs b/tests/codegen/float/f16.rs
@@ -1,4 +1,4 @@
-// 32-bit x86 returns `f32` and `f64` differently to avoid the x87 stack.
+// 32-bit x86 returns float types differently to avoid the x87 stack.
 // 32-bit systems will return 128bit values using a return area pointer.
 //@ revisions: x86 bit32 bit64
 //@[x86] only-x86
@@ -58,42 +58,44 @@ pub fn f16_le(a: f16, b: f16) -> bool {
  a <= b
 }
 
-// CHECK-LABEL: half @f16_neg(
+// This is where we check the argument and return ABI for f16.
+// other-LABEL: half @f16_neg(half
+// x86-LABEL: i16 @f16_neg(half
 #[no_mangle]
 pub fn f16_neg(a: f16) -> f16 {
  // CHECK: fneg half %{{.+}}
  -a
 }
 
-// CHECK-LABEL: half @f16_add(
+// CHECK-LABEL: @f16_add
 #[no_mangle]
 pub fn f16_add(a: f16, b: f16) -> f16 {
  // CHECK: fadd half %{{.+}}, %{{.+}}
  a + b
 }
 
-// CHECK-LABEL: half @f16_sub(
+// CHECK-LABEL: @f16_sub
 #[no_mangle]
 pub fn f16_sub(a: f16, b: f16) -> f16 {
  // CHECK: fsub half %{{.+}}, %{{.+}}
  a - b
 }
 
-// CHECK-LABEL: half @f16_mul(
+// CHECK-LABEL: @f16_mul
 #[no_mangle]
 pub fn f16_mul(a: f16, b: f16) -> f16 {
  // CHECK: fmul half %{{.+}}, %{{.+}}
  a * b
 }
 
-// CHECK-LABEL: half @f16_div(
+// CHECK-LABEL: @f16_div
 #[no_mangle]
 pub fn f16_div(a: f16, b: f16) -> f16 {
  // CHECK: fdiv half %{{.+}}, %{{.+}}
  a / b
 }
 
-// CHECK-LABEL: half @f16_rem(
+// CHECK-LABEL: @f16_rem
 #[no_mangle]
 pub fn f16_rem(a: f16, b: f16) -> f16 {
  // CHECK: frem half %{{.+}}, %{{.+}}
@@ -142,10 +144,13 @@ pub fn f16_rem_assign(a: &mut f16, b: f16) {
 
 /* float to float conversions */
 
-// CHECK-LABEL: half @f16_as_self(
+// other-LABEL: half @f16_as_self(
+// x86-LABEL: i16 @f16_as_self(
 #[no_mangle]
 pub fn f16_as_self(a: f16) -> f16 {
- // CHECK: ret half %{{.+}}
+ // other-CHECK: ret half %{{.+}}
+ // x86-CHECK: bitcast half
+ // x86-CHECK: ret i16
  a as f16
 }
 
@@ -176,21 +181,21 @@ pub fn f16_as_f128(a: f16) -> f128 {
  a as f128
 }
 
-// CHECK-LABEL: half @f32_as_f16(
+// CHECK-LABEL: @f32_as_f16
 #[no_mangle]
 pub fn f32_as_f16(a: f32) -> f16 {
  // CHECK: fptrunc float %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @f64_as_f16(
+// CHECK-LABEL: @f64_as_f16
 #[no_mangle]
 pub fn f64_as_f16(a: f64) -> f16 {
  // CHECK: fptrunc double %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @f128_as_f16(
+// CHECK-LABEL: @f128_as_f16
 #[no_mangle]
 pub fn f128_as_f16(a: f128) -> f16 {
  // CHECK: fptrunc fp128 %{{.+}} to half
@@ -273,70 +278,70 @@ pub fn f16_as_i128(a: f16) -> i128 {
 
 /* int to float conversions */
 
-// CHECK-LABEL: half @u8_as_f16(
+// CHECK-LABEL: @u8_as_f16
 #[no_mangle]
 pub fn u8_as_f16(a: u8) -> f16 {
  // CHECK: uitofp i8 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @u16_as_f16(
+// CHECK-LABEL: @u16_as_f16
 #[no_mangle]
 pub fn u16_as_f16(a: u16) -> f16 {
  // CHECK: uitofp i16 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @u32_as_f16(
+// CHECK-LABEL: @u32_as_f16
 #[no_mangle]
 pub fn u32_as_f16(a: u32) -> f16 {
  // CHECK: uitofp i32 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @u64_as_f16(
+// CHECK-LABEL: @u64_as_f16
 #[no_mangle]
 pub fn u64_as_f16(a: u64) -> f16 {
  // CHECK: uitofp i64 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @u128_as_f16(
+// CHECK-LABEL: @u128_as_f16
 #[no_mangle]
 pub fn u128_as_f16(a: u128) -> f16 {
  // CHECK: uitofp i128 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @i8_as_f16(
+// CHECK-LABEL: @i8_as_f16
 #[no_mangle]
 pub fn i8_as_f16(a: i8) -> f16 {
  // CHECK: sitofp i8 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @i16_as_f16(
+// CHECK-LABEL: @i16_as_f16
 #[no_mangle]
 pub fn i16_as_f16(a: i16) -> f16 {
  // CHECK: sitofp i16 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @i32_as_f16(
+// CHECK-LABEL: @i32_as_f16
 #[no_mangle]
 pub fn i32_as_f16(a: i32) -> f16 {
  // CHECK: sitofp i32 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @i64_as_f16(
+// CHECK-LABEL: @i64_as_f16
 #[no_mangle]
 pub fn i64_as_f16(a: i64) -> f16 {
  // CHECK: sitofp i64 %{{.+}} to half
  a as f16
 }
 
-// CHECK-LABEL: half @i128_as_f16(
+// CHECK-LABEL: @i128_as_f16
 #[no_mangle]
 pub fn i128_as_f16(a: i128) -> f16 {
  // CHECK: sitofp i128 %{{.+}} to half