Auto merge of #127001 - beetrees:f16-debuginfo, r=michaelwoerister

Add Natvis visualiser and debuginfo tests for `f16`

To render `f16`s in debuggers on MSVC targets, this PR changes the compiler to output `f16`s as `struct f16 { bits: u16 }`, and includes a Natvis visualiser that manually converts the `f16`'s bits to a `float` which is can then be displayed by debuggers. `gdb`, `lldb` and `cdb` tests are also included for `f16` .

`f16`/`f128` MSVC debug info issue: #121837
Tracking issue: #116909

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -705,17 +705,51 @@ impl MsvcBasicName for ty::UintTy {
 
 impl MsvcBasicName for ty::FloatTy {
     fn msvc_basic_name(self) -> &'static str {
-        // FIXME: f16 and f128 have no MSVC representation. We could improve the debuginfo.
-        // See: <https://github.com/rust-lang/rust/pull/114607/files#r1454683264>
+        // FIXME(f16_f128): `f16` and `f128` have no MSVC representation. We could improve the
+        // debuginfo. See: <https://github.com/rust-lang/rust/issues/121837>
         match self {
-            ty::FloatTy::F16 => "half",
+            ty::FloatTy::F16 => {
+                bug!("`f16` should have been handled in `build_basic_type_di_node`")
+            }
             ty::FloatTy::F32 => "float",
             ty::FloatTy::F64 => "double",
             ty::FloatTy::F128 => "fp128",
         }
     }
 }
 
+fn build_cpp_f16_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) -> DINodeCreationResult<'ll> {
+    // MSVC has no native support for `f16`. Instead, emit `struct f16 { bits: u16 }` to allow the
+    // `f16`'s value to be displayed using a Natvis visualiser in `intrinsic.natvis`.
+    let float_ty = cx.tcx.types.f16;
+    let bits_ty = cx.tcx.types.u16;
+    type_map::build_type_with_children(
+        cx,
+        type_map::stub(
+            cx,
+            Stub::Struct,
+            UniqueTypeId::for_ty(cx.tcx, float_ty),
+            "f16",
+            cx.size_and_align_of(float_ty),
+            NO_SCOPE_METADATA,
+            DIFlags::FlagZero,
+        ),
+        // Fields:
+        |cx, float_di_node| {
+            smallvec![build_field_di_node(
+                cx,
+                float_di_node,
+                "bits",
+                cx.size_and_align_of(bits_ty),
+                Size::ZERO,
+                DIFlags::FlagZero,
+                type_di_node(cx, bits_ty),
+            )]
+        },
+        NO_GENERICS,
+    )
+}
+
 fn build_basic_type_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     t: Ty<'tcx>,
@@ -739,6 +773,9 @@ fn build_basic_type_di_node<'ll, 'tcx>(
         ty::Char => ("char", DW_ATE_UTF),
         ty::Int(int_ty) if cpp_like_debuginfo => (int_ty.msvc_basic_name(), DW_ATE_signed),
         ty::Uint(uint_ty) if cpp_like_debuginfo => (uint_ty.msvc_basic_name(), DW_ATE_unsigned),
+        ty::Float(ty::FloatTy::F16) if cpp_like_debuginfo => {
+            return build_cpp_f16_di_node(cx);
+        }
         ty::Float(float_ty) if cpp_like_debuginfo => (float_ty.msvc_basic_name(), DW_ATE_float),
         ty::Int(int_ty) => (int_ty.name_str(), DW_ATE_signed),
         ty::Uint(uint_ty) => (uint_ty.name_str(), DW_ATE_unsigned),

src/etc/natvis/intrinsic.natvis

@@ -33,6 +33,32 @@
       </ArrayItems>
     </Expand>
   </Type>
+  <Type Name="f16">
+    <Intrinsic Name="sign_mask" Expression="(unsigned __int16) 0x8000" />
+    <Intrinsic Name="exponent_mask" Expression="(unsigned __int16) 0x7c00" />
+    <Intrinsic Name="significand_mask" Expression="(unsigned __int16) 0x03ff" />
+    <Intrinsic Name="sign_bit" Expression="(unsigned __int16) (bits &amp; sign_mask())" />
+    <Intrinsic Name="exponent_bits" Expression="(unsigned __int16) (bits &amp; exponent_mask())" />
+    <Intrinsic Name="significand_bits" Expression="(unsigned __int16) (bits &amp; significand_mask())" />
+
+    <Intrinsic Name="if_set" Expression="(bits &amp; mask) != 0 ? value : 1.0">
+      <Parameter Name="mask" Type="unsigned __int16" />
+      <Parameter Name="value" Type="float" />
+    </Intrinsic>
+    <!-- Calculates 2**exp without needing a pow function. Each float in if_set() is the square of the previous float. 32768 == 2.pow(bias), bias == 15 -->
+    <Intrinsic Name="two_pow_exponent" Expression="if_set(0x0400, 2.0) * if_set(0x0800, 4.0) * if_set(0x1000, 16.0) * if_set(0x2000, 256.0) * if_set(0x4000, 65536.0) / 32768.0" />
+    <!-- Calculates 0.significand, without any implicit bit. 1024 == 2.pow(explicit significand width), explicit significand width == 10 -->
+    <Intrinsic Name="raw_significand" Expression="((float) significand_bits()) / 1024.0" />
+    <Intrinsic Name="sign" Expression="sign_bit() == 0 ? 1.0 : -1.0" />
+
+    <DisplayString Condition="bits == 0x7c00">inf</DisplayString>
+    <DisplayString Condition="bits == 0xfc00">-inf</DisplayString>
+    <DisplayString Condition="exponent_bits() == exponent_mask()">NaN</DisplayString>
+    <!-- Subnormal or zero (16384 == 2.pow(bias - 1), bias - 1 == 14) -->
+    <DisplayString Condition="exponent_bits() == 0">{(float) (sign() * raw_significand() / 16384.0)}</DisplayString>
+    <!-- Normal -->
+    <DisplayString>{(float) (sign() * (raw_significand() + 1.0) * two_pow_exponent())}</DisplayString>
+  </Type>
   <Type Name="tuple$&lt;&gt;">
     <DisplayString>()</DisplayString>
   </Type>

tests/debuginfo/basic-types-globals-metadata.rs

@@ -39,6 +39,9 @@
 // gdbg-command:whatis 'basic_types_globals_metadata::U64'
 // gdbr-command:whatis basic_types_globals_metadata::U64
 // gdb-check:type = u64
+// gdbg-command:whatis 'basic_types_globals_metadata::F16'
+// gdbr-command:whatis basic_types_globals_metadata::F16
+// gdb-check:type = f16
 // gdbg-command:whatis 'basic_types_globals_metadata::F32'
 // gdbr-command:whatis basic_types_globals_metadata::F32
 // gdb-check:type = f32
@@ -51,6 +54,7 @@
 #![allow(dead_code)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 // N.B. These are `mut` only so they don't constant fold away.
 static mut B: bool = false;
@@ -65,13 +69,14 @@ static mut U8: u8 = 100;
 static mut U16: u16 = 16;
 static mut U32: u32 = 32;
 static mut U64: u64 = 64;
+static mut F16: f16 = 1.5;
 static mut F32: f32 = 2.5;
 static mut F64: f64 = 3.5;
 
 fn main() {
     _zzz(); // #break
 
-    let a = unsafe { (B, I, C, I8, I16, I32, I64, U, U8, U16, U32, U64, F32, F64) };
+    let a = unsafe { (B, I, C, I8, I16, I32, I64, U, U8, U16, U32, U64, F16, F32, F64) };
 }
 
 fn _zzz() {()}

tests/debuginfo/basic-types-globals.rs

@@ -49,17 +49,21 @@
 // gdbg-command:print 'basic_types_globals::U64'
 // gdbr-command:print U64
 // gdb-check:$12 = 64
+// gdbg-command:print 'basic_types_globals::F16'
+// gdbr-command:print F16
+// gdb-check:$13 = 1.5
 // gdbg-command:print 'basic_types_globals::F32'
 // gdbr-command:print F32
-// gdb-check:$13 = 2.5
+// gdb-check:$14 = 2.5
 // gdbg-command:print 'basic_types_globals::F64'
 // gdbr-command:print F64
-// gdb-check:$14 = 3.5
+// gdb-check:$15 = 3.5
 // gdb-command:continue
 
 #![allow(unused_variables)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 // N.B. These are `mut` only so they don't constant fold away.
 static mut B: bool = false;
@@ -74,13 +78,14 @@ static mut U8: u8 = 100;
 static mut U16: u16 = 16;
 static mut U32: u32 = 32;
 static mut U64: u64 = 64;
+static mut F16: f16 = 1.5;
 static mut F32: f32 = 2.5;
 static mut F64: f64 = 3.5;
 
 fn main() {
     _zzz(); // #break
 
-    let a = unsafe { (B, I, C, I8, I16, I32, I64, U, U8, U16, U32, U64, F32, F64) };
+    let a = unsafe { (B, I, C, I8, I16, I32, I64, U, U8, U16, U32, U64, F16, F32, F64) };
 }
 
 fn _zzz() {()}

tests/debuginfo/basic-types-metadata.rs

@@ -29,6 +29,8 @@
 // gdb-check:type = u32
 // gdb-command:whatis u64
 // gdb-check:type = u64
+// gdb-command:whatis f16
+// gdb-check:type = f16
 // gdb-command:whatis f32
 // gdb-check:type = f32
 // gdb-command:whatis f64
@@ -66,6 +68,7 @@
 #![allow(unused_variables)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 fn main() {
     let unit: () = ();
@@ -81,6 +84,7 @@ fn main() {
     let u16: u16 = 16;
     let u32: u32 = 32;
     let u64: u64 = 64;
+    let f16: f16 = 1.5;
     let f32: f32 = 2.5;
     let f64: f64 = 3.5;
     let fnptr : fn() = _zzz;

tests/debuginfo/basic-types-mut-globals.rs

@@ -5,7 +5,6 @@
 // its numerical value.
 
 //@ min-lldb-version: 310
-//@ ignore-gdb // Test temporarily ignored due to debuginfo tests being disabled, see PR 47155
 
 //@ compile-flags:-g
 
@@ -49,62 +48,69 @@
 // gdbg-command:print 'basic_types_mut_globals::U64'
 // gdbr-command:print U64
 // gdb-check:$12 = 64
+// gdbg-command:print 'basic_types_mut_globals::F16'
+// gdbr-command:print F16
+// gdb-check:$13 = 1.5
 // gdbg-command:print 'basic_types_mut_globals::F32'
 // gdbr-command:print F32
-// gdb-check:$13 = 2.5
+// gdb-check:$14 = 2.5
 // gdbg-command:print 'basic_types_mut_globals::F64'
 // gdbr-command:print F64
-// gdb-check:$14 = 3.5
+// gdb-check:$15 = 3.5
 // gdb-command:continue
 
 // Check new values
 // gdbg-command:print 'basic_types_mut_globals'::B
 // gdbr-command:print B
-// gdb-check:$15 = true
+// gdb-check:$16 = true
 // gdbg-command:print 'basic_types_mut_globals'::I
 // gdbr-command:print I
-// gdb-check:$16 = 2
+// gdb-check:$17 = 2
 // gdbg-command:print/d 'basic_types_mut_globals'::C
 // gdbr-command:print C
-// gdbg-check:$17 = 102
-// gdbr-check:$17 = 102 'f'
+// gdbg-check:$18 = 102
+// gdbr-check:$18 = 102 'f'
 // gdbg-command:print/d 'basic_types_mut_globals'::I8
 // gdbr-command:print/d I8
-// gdb-check:$18 = 78
+// gdb-check:$19 = 78
 // gdbg-command:print 'basic_types_mut_globals'::I16
 // gdbr-command:print I16
-// gdb-check:$19 = -26
+// gdb-check:$20 = -26
 // gdbg-command:print 'basic_types_mut_globals'::I32
 // gdbr-command:print I32
-// gdb-check:$20 = -12
+// gdb-check:$21 = -12
 // gdbg-command:print 'basic_types_mut_globals'::I64
 // gdbr-command:print I64
-// gdb-check:$21 = -54
+// gdb-check:$22 = -54
 // gdbg-command:print 'basic_types_mut_globals'::U
 // gdbr-command:print U
-// gdb-check:$22 = 5
+// gdb-check:$23 = 5
 // gdbg-command:print/d 'basic_types_mut_globals'::U8
 // gdbr-command:print/d U8
-// gdb-check:$23 = 20
+// gdb-check:$24 = 20
 // gdbg-command:print 'basic_types_mut_globals'::U16
 // gdbr-command:print U16
-// gdb-check:$24 = 32
+// gdb-check:$25 = 32
 // gdbg-command:print 'basic_types_mut_globals'::U32
 // gdbr-command:print U32
-// gdb-check:$25 = 16
+// gdb-check:$26 = 16
 // gdbg-command:print 'basic_types_mut_globals'::U64
 // gdbr-command:print U64
-// gdb-check:$26 = 128
+// gdb-check:$27 = 128
+// gdbg-command:print 'basic_types_mut_globals'::F16
+// gdbr-command:print F16
+// gdb-check:$28 = 2.25
 // gdbg-command:print 'basic_types_mut_globals'::F32
 // gdbr-command:print F32
-// gdb-check:$27 = 5.75
+// gdb-check:$29 = 5.75
 // gdbg-command:print 'basic_types_mut_globals'::F64
 // gdbr-command:print F64
-// gdb-check:$28 = 9.25
+// gdb-check:$30 = 9.25
 
 #![allow(unused_variables)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 static mut B: bool = false;
 static mut I: isize = -1;
@@ -118,6 +124,7 @@ static mut U8: u8 = 100;
 static mut U16: u16 = 16;
 static mut U32: u32 = 32;
 static mut U64: u64 = 64;
+static mut F16: f16 = 1.5;
 static mut F32: f32 = 2.5;
 static mut F64: f64 = 3.5;
 
@@ -137,6 +144,7 @@ fn main() {
         U16 = 32;
         U32 = 16;
         U64 = 128;
+        F16 = 2.25;
         F32 = 5.75;
         F64 = 9.25;
     }

tests/debuginfo/basic-types.rs

@@ -39,13 +39,15 @@
 // gdb-check:$11 = 32
 // gdb-command:print u64
 // gdb-check:$12 = 64
+// gdb-command:print f16
+// gdb-check:$13 = 1.5
 // gdb-command:print f32
-// gdb-check:$13 = 2.5
+// gdb-check:$14 = 2.5
 // gdb-command:print f64
-// gdb-check:$14 = 3.5
+// gdb-check:$15 = 3.5
 // gdb-command:print s
-// gdbg-check:$15 = {data_ptr = [...] "Hello, World!", length = 13}
-// gdbr-check:$15 = "Hello, World!"
+// gdbg-check:$16 = {data_ptr = [...] "Hello, World!", length = 13}
+// gdbr-check:$16 = "Hello, World!"
 
 // === LLDB TESTS ==================================================================================
 
@@ -122,6 +124,8 @@
 // cdb-check:u32              : 0x20 [Type: unsigned int]
 // cdb-command:dx u64
 // cdb-check:u64              : 0x40 [Type: unsigned __int64]
+// cdb-command:dx f16
+// cdb-check:f16              : 1.500000 [Type: f16]
 // cdb-command:dx f32
 // cdb-check:f32              : 2.500000 [Type: float]
 // cdb-command:dx f64
@@ -134,6 +138,7 @@
 #![allow(unused_variables)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 fn main() {
     let b: bool = false;
@@ -148,6 +153,7 @@ fn main() {
     let u16: u16 = 16;
     let u32: u32 = 32;
     let u64: u64 = 64;
+    let f16: f16 = 1.5;
     let f32: f32 = 2.5;
     let f64: f64 = 3.5;
     let s: &str = "Hello, World!";

tests/debuginfo/borrowed-basic.rs

@@ -42,11 +42,14 @@
 // gdb-command:print *u64_ref
 // gdb-check:$12 = 64
 
+// gdb-command:print *f16_ref
+// gdb-check:$13 = 1.5
+
 // gdb-command:print *f32_ref
-// gdb-check:$13 = 2.5
+// gdb-check:$14 = 2.5
 
 // gdb-command:print *f64_ref
-// gdb-check:$14 = 3.5
+// gdb-check:$15 = 3.5
 
 
 // === LLDB TESTS ==================================================================================
@@ -100,6 +103,10 @@
 // lldbg-check:[...] 64
 // lldbr-check:(u64) *u64_ref = 64
 
+// lldb-command:v *f16_ref
+// lldbg-check:[...] 1.5
+// lldbr-check:(f16) *f16_ref = 1.5
+
 // lldb-command:v *f32_ref
 // lldbg-check:[...] 2.5
 // lldbr-check:(f32) *f32_ref = 2.5
@@ -111,6 +118,7 @@
 #![allow(unused_variables)]
 #![feature(omit_gdb_pretty_printer_section)]
 #![omit_gdb_pretty_printer_section]
+#![feature(f16)]
 
 fn main() {
     let bool_val: bool = true;
@@ -149,6 +157,9 @@ fn main() {
     let u64_val: u64 = 64;
     let u64_ref: &u64 = &u64_val;
 
+    let f16_val: f16 = 1.5;
+    let f16_ref: &f16 = &f16_val;
+
     let f32_val: f32 = 2.5;
     let f32_ref: &f32 = &f32_val;