macros: move debug_printf macro to separate mod

Author: Firestar99

crates/spirv-std/macros/src/debug_printf.rs

@@ -0,0 +1,249 @@
+use proc_macro::TokenStream;
+use proc_macro2::Span;
+use std::fmt::Write;
+
+pub struct DebugPrintfInput {
+    pub span: Span,
+    pub format_string: String,
+    pub variables: Vec<syn::Expr>,
+}
+
+impl syn::parse::Parse for DebugPrintfInput {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::parse::Result<Self> {
+        let span = input.span();
+
+        if input.is_empty() {
+            return Ok(Self {
+                span,
+                format_string: Default::default(),
+                variables: Default::default(),
+            });
+        }
+
+        let format_string = input.parse::<syn::LitStr>()?;
+        if !input.is_empty() {
+            input.parse::<syn::token::Comma>()?;
+        }
+        let variables =
+            syn::punctuated::Punctuated::<syn::Expr, syn::token::Comma>::parse_terminated(input)?;
+
+        Ok(Self {
+            span,
+            format_string: format_string.value(),
+            variables: variables.into_iter().collect(),
+        })
+    }
+}
+
+fn parsing_error(message: &str, span: Span) -> TokenStream {
+    syn::Error::new(span, message).to_compile_error().into()
+}
+
+enum FormatType {
+    Scalar {
+        ty: proc_macro2::TokenStream,
+    },
+    Vector {
+        ty: proc_macro2::TokenStream,
+        width: usize,
+    },
+}
+
+pub fn debug_printf_inner(input: DebugPrintfInput) -> TokenStream {
+    let DebugPrintfInput {
+        format_string,
+        variables,
+        span,
+    } = input;
+
+    fn map_specifier_to_type(
+        specifier: char,
+        chars: &mut std::str::Chars<'_>,
+    ) -> Option<proc_macro2::TokenStream> {
+        let mut peekable = chars.peekable();
+
+        Some(match specifier {
+            'd' | 'i' => quote::quote! { i32 },
+            'o' | 'x' | 'X' => quote::quote! { u32 },
+            'a' | 'A' | 'e' | 'E' | 'f' | 'F' | 'g' | 'G' => quote::quote! { f32 },
+            'u' => {
+                if matches!(peekable.peek(), Some('l')) {
+                    chars.next();
+                    quote::quote! { u64 }
+                } else {
+                    quote::quote! { u32 }
+                }
+            }
+            'l' => {
+                if matches!(peekable.peek(), Some('u' | 'x')) {
+                    chars.next();
+                    quote::quote! { u64 }
+                } else {
+                    return None;
+                }
+            }
+            _ => return None,
+        })
+    }
+
+    let mut chars = format_string.chars();
+    let mut format_arguments = Vec::new();
+
+    while let Some(mut ch) = chars.next() {
+        if ch == '%' {
+            ch = match chars.next() {
+                Some('%') => continue,
+                None => return parsing_error("Unterminated format specifier", span),
+                Some(ch) => ch,
+            };
+
+            let mut has_precision = false;
+
+            while ch.is_ascii_digit() {
+                ch = match chars.next() {
+                    Some(ch) => ch,
+                    None => {
+                        return parsing_error(
+                            "Unterminated format specifier: missing type after precision",
+                            span,
+                        );
+                    }
+                };
+
+                has_precision = true;
+            }
+
+            if has_precision && ch == '.' {
+                ch = match chars.next() {
+                    Some(ch) => ch,
+                    None => {
+                        return parsing_error(
+                            "Unterminated format specifier: missing type after decimal point",
+                            span,
+                        );
+                    }
+                };
+
+                while ch.is_ascii_digit() {
+                    ch = match chars.next() {
+                        Some(ch) => ch,
+                        None => {
+                            return parsing_error(
+                                "Unterminated format specifier: missing type after fraction precision",
+                                span,
+                            );
+                        }
+                    };
+                }
+            }
+
+            if ch == 'v' {
+                let width = match chars.next() {
+                    Some('2') => 2,
+                    Some('3') => 3,
+                    Some('4') => 4,
+                    Some(ch) => {
+                        return parsing_error(&format!("Invalid width for vector: {ch}"), span);
+                    }
+                    None => return parsing_error("Missing vector dimensions specifier", span),
+                };
+
+                ch = match chars.next() {
+                    Some(ch) => ch,
+                    None => return parsing_error("Missing vector type specifier", span),
+                };
+
+                let ty = match map_specifier_to_type(ch, &mut chars) {
+                    Some(ty) => ty,
+                    _ => {
+                        return parsing_error(
+                            &format!("Unrecognised vector type specifier: '{ch}'"),
+                            span,
+                        );
+                    }
+                };
+
+                format_arguments.push(FormatType::Vector { ty, width });
+            } else {
+                let ty = match map_specifier_to_type(ch, &mut chars) {
+                    Some(ty) => ty,
+                    _ => {
+                        return parsing_error(
+                            &format!("Unrecognised format specifier: '{ch}'"),
+                            span,
+                        );
+                    }
+                };
+
+                format_arguments.push(FormatType::Scalar { ty });
+            }
+        }
+    }
+
+    if format_arguments.len() != variables.len() {
+        return syn::Error::new(
+            span,
+            format!(
+                "{} % arguments were found, but {} variables were given",
+                format_arguments.len(),
+                variables.len()
+            ),
+        )
+        .to_compile_error()
+        .into();
+    }
+
+    let mut variable_idents = String::new();
+    let mut input_registers = Vec::new();
+    let mut op_loads = Vec::new();
+
+    for (i, (variable, format_argument)) in variables.into_iter().zip(format_arguments).enumerate()
+    {
+        let ident = quote::format_ident!("_{}", i);
+
+        let _ = write!(variable_idents, "%{ident} ");
+
+        let assert_fn = match format_argument {
+            FormatType::Scalar { ty } => {
+                quote::quote! { spirv_std::debug_printf_assert_is_type::<#ty> }
+            }
+            FormatType::Vector { ty, width } => {
+                quote::quote! { spirv_std::debug_printf_assert_is_vector::<#ty, _, #width> }
+            }
+        };
+
+        input_registers.push(quote::quote! {
+            #ident = in(reg) &#assert_fn(#variable),
+        });
+
+        let op_load = format!("%{ident} = OpLoad _ {{{ident}}}");
+
+        op_loads.push(quote::quote! {
+            #op_load,
+        });
+    }
+
+    let input_registers = input_registers
+        .into_iter()
+        .collect::<proc_macro2::TokenStream>();
+    let op_loads = op_loads.into_iter().collect::<proc_macro2::TokenStream>();
+    // Escapes the '{' and '}' characters in the format string.
+    // Since the `asm!` macro expects '{' '}' to surround its arguments, we have to use '{{' and '}}' instead.
+    // The `asm!` macro will then later turn them back into '{' and '}'.
+    let format_string = format_string.replace('{', "{{").replace('}', "}}");
+
+    let op_string = format!("%string = OpString {format_string:?}");
+
+    let output = quote::quote! {
+        ::core::arch::asm!(
+            "%void = OpTypeVoid",
+            #op_string,
+            "%debug_printf = OpExtInstImport \"NonSemantic.DebugPrintf\"",
+            #op_loads
+            concat!("%result = OpExtInst %void %debug_printf 1 %string ", #variable_idents),
+            #input_registers
+        )
+    };
+
+    output.into()
+}