implement floor and ceil with global assembly on i586

Author: folkertdev

libm/src/math/arch/i586.rs

@@ -6,31 +6,8 @@
 ///
 /// Based on https://github.com/NetBSD/src/blob/trunk/lib/libm/arch/i387/s_ceil.S
 /// (written by J.T. Conklin <[email protected]>).
-#[unsafe(naked)]
-pub extern "C" fn ceil(_: f64) -> f64 {
-    core::arch::naked_asm!(
-        "pushl  %ebp",
-        "movl   %esp,%ebp",
-        "subl   $8,%esp",
-        // Store fpu control word.
-        "fstcw   -4(%ebp)",
-        "movw    -4(%ebp),%dx",
-        // Round towards +oo.
-        "orw $0x0800,%dx",
-        "andw    $0xfbff,%dx",
-        "movw    %dx,-8(%ebp)",
-        // Load modified control word
-        "fldcw   -8(%ebp)",
-        // Round.
-        "fldl    8(%ebp)",
-        "frndint",
-        // Restore original control word.
-        "fldcw   -4(%ebp)",
-        // Restore esp and ebp and return
-        "leave",
-        "ret",
-        options(att_syntax)
-    )
+pub fn ceil(x: f64) -> f64 {
+    unsafe { ceil_helper(x) }
 }
 
 /// Use an alternative implementation on x86, because the
@@ -39,29 +16,73 @@ pub extern "C" fn ceil(_: f64) -> f64 {
 ///
 /// Based on https://github.com/NetBSD/src/blob/trunk/lib/libm/arch/i387/s_floor.S
 /// (written by J.T. Conklin <[email protected]>).
-#[unsafe(naked)]
-pub extern "C" fn floor(_: f64) -> f64 {
-    core::arch::naked_asm!(
-        "pushl  %ebp",
-        "movl   %esp,%ebp",
-        "subl   $8,%esp",
-        // Store fpu control word.
-        "fstcw   -4(%ebp)",
-        "movw    -4(%ebp),%dx",
-        // Round towards -oo.
-        "orw	$0x0400,%dx",
-        "andw	$0xf7ff,%dx",
-        "movw   %dx,-8(%ebp)",
-        // Load modified control word
-        "fldcw   -8(%ebp)",
-        // Round.
-        "fldl    8(%ebp)",
-        "frndint",
-        // Restore original control word.
-        "fldcw   -4(%ebp)",
-        // Restore esp and ebp and return
-        "leave",
-        "ret",
-        options(att_syntax)
-    )
+pub fn floor(x: f64) -> f64 {
+    unsafe { floor_helper(x) }
 }
+
+extern "cdecl" {
+    fn ceil_helper(_: f64) -> f64;
+    fn floor_helper(_: f64) -> f64;
+}
+
+core::arch::global_asm!(
+    ".pushsection .text.{ceil},\"ax\",@progbits",
+    ".p2align 2",
+    ".global {ceil}",
+    ".type {ceil}, @function",
+    "{ceil}:",
+    "pushl  %ebp",
+    "movl   %esp,%ebp",
+    "subl   $8,%esp",
+    // Store fpu control word.
+    "fstcw   -4(%ebp)",
+    "movw    -4(%ebp),%dx",
+    // Round towards +oo.
+    "orw $0x0800,%dx",
+    "andw    $0xfbff,%dx",
+    "movw    %dx,-8(%ebp)",
+    // Load modified control word
+    "fldcw   -8(%ebp)",
+    // Round.
+    "fldl    8(%ebp)",
+    "frndint",
+    // Restore original control word.
+    "fldcw   -4(%ebp)",
+    // Restore esp and ebp and return
+    "leave",
+    "ret",
+    ".size {ceil}, . - {ceil}",
+    options(att_syntax),
+    ceil = sym ceil_helper,
+);
+
+core::arch::global_asm!(
+    ".pushsection .text.{floor},\"ax\",@progbits",
+    ".p2align 2",
+    ".global {floor}",
+    ".type {floor}, @function",
+    "{floor}:",
+    "pushl  %ebp",
+    "movl   %esp,%ebp",
+    "subl   $8,%esp",
+    // Store fpu control word.
+    "fstcw   -4(%ebp)",
+    "movw    -4(%ebp),%dx",
+    // Round towards -oo.
+    "orw	$0x0400,%dx",
+    "andw	$0xf7ff,%dx",
+    "movw   %dx,-8(%ebp)",
+    // Load modified control word
+    "fldcw   -8(%ebp)",
+    // Round.
+    "fldl    8(%ebp)",
+    "frndint",
+    // Restore original control word.
+    "fldcw   -4(%ebp)",
+    // Restore esp and ebp and return
+    "leave",
+    "ret",
+    ".size {floor}, . - {floor}",
+    options(att_syntax),
+    floor = sym floor_helper,
+);