Cleanup asm a bit

* Use a shared header file to deduplicate some directives * Guarantee hidden visibility for functions * Enable gc-sections on macOS x86_64 * Add `.type` annotations for ARM
bytecodealliance · Feb 5, 2021 · 67d34f5 · 67d34f5
1 parent 013d0c1
commit 67d34f5
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Showing 5 changed files with 77 additions and 51 deletions.
diff --git a/crates/fiber/src/arch/aarch64.S b/crates/fiber/src/arch/aarch64.S
@@ -8,12 +8,10 @@
 // Also at this time this file is heavily based off the x86_64 file, so you'll
 // probably want to read that one as well.
 
-#define GLOBL(fnname) .globl fnname
-#define TYPE(fnname) .type fnname,@function
-#define FUNCTION(fnname) fnname
-#define SIZE(fnname) .size fnname,.-fnname
+#include "header.h"
 
 // fn(top_of_stack(%x0): *mut u8)
+HIDDEN(wasmtime_fiber_switch)
 GLOBL(wasmtime_fiber_switch)
 .p2align 2
 TYPE(wasmtime_fiber_switch)
@@ -58,11 +56,12 @@ SIZE(wasmtime_fiber_switch)
 //    entry_point(%x1): extern fn(*mut u8, *mut u8),
 //    entry_arg0(%x2): *mut u8,
 // )
+HIDDEN(wasmtime_fiber_init)
 GLOBL(wasmtime_fiber_init)
 .p2align 2
 TYPE(wasmtime_fiber_init)
 FUNCTION(wasmtime_fiber_init):
-    adr x8, wasmtime_fiber_start
+    adr x8, FUNCTION(wasmtime_fiber_start)
     stp x0, x8, [x0, -0x28] // x0 => x19, x8 => lr
     stp x2, x1, [x0, -0x38] // x1 => x20, x2 => x21
 
@@ -114,5 +113,10 @@ FUNCTION(wasmtime_fiber_start):
     .cfi_endproc
 SIZE(wasmtime_fiber_start)
 
-.section .note.GNU-stack,"",%progbits
-
+// This omits the `.subsections_via_symbols` directive on macOS which means we
+// can't GC specific intrinsics from this file, but it enables usage of the
+// `adr` instruction above in lieu of figuring out a slightly more complicated
+// way of implementing that.
+#ifndef CFG_TARGET_OS_macos
+FOOTER
+#endif
diff --git a/crates/fiber/src/arch/arm.S b/crates/fiber/src/arch/arm.S
@@ -8,11 +8,13 @@
 // Also at this time this file is heavily based off the x86_64 file, so you'll
 // probably want to read that one as well.
 
-#define SIZE(fnname) .size fnname,.-fnname
+#include "header.h"
 
 // fn(top_of_stack(%r0): *mut u8)
-.globl wasmtime_fiber_switch
-wasmtime_fiber_switch:
+HIDDEN(wasmtime_fiber_switch)
+GLOBL(wasmtime_fiber_switch)
+TYPE(wasmtime_fiber_switch)
+FUNCTION(wasmtime_fiber_switch):
     // Save callee-saved registers
     push {r4-r11,lr}
 
@@ -31,9 +33,11 @@ SIZE(wasmtime_fiber_switch)
 //    entry_point(%r1): extern fn(*mut u8, *mut u8),
 //    entry_arg0(%r2): *mut u8,
 // )
-.globl wasmtime_fiber_init
-wasmtime_fiber_init:
-    adr r3, wasmtime_fiber_start
+HIDDEN(wasmtime_fiber_init)
+GLOBL(wasmtime_fiber_init)
+TYPE(wasmtime_fiber_init)
+FUNCTION(wasmtime_fiber_init):
+    adr r3, FUNCTION(wasmtime_fiber_start)
     str r3, [r0, #-0x0c] // => lr
     str r0, [r0, #-0x10] // => r11
     str r1, [r0, #-0x14] // => r10
@@ -44,7 +48,7 @@ wasmtime_fiber_init:
     bx lr
 SIZE(wasmtime_fiber_init)
 
-wasmtime_fiber_start:
+FUNCTION(wasmtime_fiber_start):
 .cfi_startproc simple
     // See the x86_64 file for more commentary on what these CFI directives are
     // doing. Like over there note that the relative offsets to registers here
@@ -76,4 +80,4 @@ wasmtime_fiber_start:
     .cfi_endproc
 SIZE(wasmtime_fiber_start)
 
-.section .note.GNU-stack,"",%progbits
+FOOTER
diff --git a/crates/fiber/src/arch/header.h b/crates/fiber/src/arch/header.h
@@ -0,0 +1,36 @@
+#ifndef __wasmtime_common_h
+#define __wasmtime_common_h
+
+#if CFG_TARGET_OS_macos
+
+.section __TEXT,__text,regular,pure_instructions
+
+#define GLOBL(fnname) .globl _##fnname
+#define HIDDEN(fnname) .private_extern _##fnname
+#define TYPE(fnname)
+#define FUNCTION(fnname) _##fnname
+#define SIZE(fnname)
+
+// Tells the linker it's safe to gc symbols away if not used.
+#define FOOTER .subsections_via_symbols
+
+#else
+
+.text
+
+#define GLOBL(fnname) .globl fnname
+#define HIDDEN(fnname) .hidden fnname
+#ifdef CFG_TARGET_ARCH_arm
+#define TYPE(fnname) .type fnname,%function
+#else
+#define TYPE(fnname) .type fnname,@function
+#endif
+#define FUNCTION(fnname) fnname
+#define SIZE(fnname) .size fnname,.-fnname
+
+// Mark that we don't need executable stack.
+#define FOOTER .section .note.GNU-stack,"",%progbits
+
+#endif
+
+#endif // __wasmtime_common_h
diff --git a/crates/fiber/src/arch/x86.S b/crates/fiber/src/arch/x86.S
@@ -10,14 +10,13 @@
 // different so the reserved space at the top of the stack is 8 bytes, not 16
 // bytes. Still two pointers though.
 
-.text
-
-#define SIZE(fnname) .size fnname,.-fnname
+#include "header.h"
 
 // fn(top_of_stack: *mut u8)
-.globl wasmtime_fiber_switch
-.type wasmtime_fiber_switch,@function
-wasmtime_fiber_switch:
+HIDDEN(wasmtime_fiber_switch)
+GLOBL(wasmtime_fiber_switch)
+TYPE(wasmtime_fiber_switch)
+FUNCTION(wasmtime_fiber_switch):
     // Load our stack-to-use
     mov 0x4(%esp), %eax
     mov -0x8(%eax), %ecx
@@ -45,9 +44,10 @@ SIZE(wasmtime_fiber_switch)
 //    entry_point: extern fn(*mut u8, *mut u8),
 //    entry_arg0: *mut u8,
 // )
-.globl wasmtime_fiber_init
-.type wasmtime_fiber_init,@function
-wasmtime_fiber_init:
+HIDDEN(wasmtime_fiber_init)
+GLOBL(wasmtime_fiber_init)
+TYPE(wasmtime_fiber_init)
+FUNCTION(wasmtime_fiber_init):
     mov 4(%esp), %eax
 
     // move top_of_stack to the 2nd argument
@@ -59,7 +59,7 @@ wasmtime_fiber_init:
 
     // Move our start function to the return address which the `ret` in
     // `wasmtime_fiber_start` will return to.
-    lea wasmtime_fiber_start, %ecx
+    lea FUNCTION(wasmtime_fiber_start), %ecx
     mov %ecx, -0x14(%eax)
 
     // And move `entry_point` to get loaded into `%ebp` through the context
@@ -82,8 +82,8 @@ wasmtime_fiber_init:
     ret
 SIZE(wasmtime_fiber_init)
 
-.type wasmtime_fiber_start,@function
-wasmtime_fiber_start:
+TYPE(wasmtime_fiber_start)
+FUNCTION(wasmtime_fiber_start):
 .cfi_startproc simple
     .cfi_escape 0x0f, /* DW_CFA_def_cfa_expression */ \
         5,            /* the byte length of this expression */ \
@@ -104,6 +104,4 @@ wasmtime_fiber_start:
     .cfi_endproc
 SIZE(wasmtime_fiber_start)
 
-// Mark that we don't need executable stack.
-.section .note.GNU-stack,"",%progbits
-
+FOOTER
diff --git a/crates/fiber/src/arch/x86_64.S b/crates/fiber/src/arch/x86_64.S
@@ -5,25 +5,10 @@
 // all the other bits. Documentation tries to reference various bits here and
 // there but try to make sure to read over everything before tweaking things!
 
-.text
-
-#if CFG_TARGET_OS_macos
-
-#define GLOBL(fnname) .globl _##fnname
-#define TYPE(fnname)
-#define FUNCTION(fnname) _##fnname
-#define SIZE(fnname)
-
-#else
-
-#define GLOBL(fnname) .globl fnname
-#define TYPE(fnname) .type fnname,@function
-#define FUNCTION(fnname) fnname
-#define SIZE(fnname) .size fnname,.-fnname
-
-#endif
+#include "header.h"
 
 // fn(top_of_stack(%rdi): *mut u8)
+HIDDEN(wasmtime_fiber_switch)
 GLOBL(wasmtime_fiber_switch)
 .align 16
 TYPE(wasmtime_fiber_switch)
@@ -63,6 +48,7 @@ SIZE(wasmtime_fiber_switch)
 //    entry_point(%rsi): extern fn(*mut u8, *mut u8),
 //    entry_arg0(%rdx): *mut u8,
 // )
+HIDDEN(wasmtime_fiber_init)
 GLOBL(wasmtime_fiber_init)
 .align 16
 TYPE(wasmtime_fiber_init)
@@ -169,7 +155,5 @@ FUNCTION(wasmtime_fiber_start):
     .cfi_endproc
 SIZE(wasmtime_fiber_start)
 
-// Mark that we don't need executable stack.
-#if defined(__ELF__)
-.section .note.GNU-stack,"",%progbits
-#endif
+FOOTER
+