zig

commit ef72b91ac2b96ba64a53b08a661e9ad83a828ee4 (tree)
parent d2f04e919c833288d5cf1efa97c25bbaae101168
Author: Alex Rønne Petersen <alex@alexrp.com>
Date:   Tue, 15 Oct 2024 21:28:42 +0200

compiler: Remove uses of defaultFunctionAlignment() in the frontend.

minFunctionAlignment() is something we can know ahead of time for any given
target because it's a matter of ABI. However, defaultFunctionAlignment() is a
matter of optimization and every backend can do it differently depending on any
number of factors. For example, LLVM will base the choice on the CPU model in
its aarch64 backend. So just don't use this value in the frontend.

Diffstat:
M
src/Sema.zig
 | 
8
++------
M
src/Type.zig
 | 
2
+-
M
src/target.zig
 | 
3
++-

3 files changed, 5 insertions(+), 8 deletions(-)
diff --git a/src/Sema.zig b/src/Sema.zig
@@ -26572,9 +26572,7 @@ fn zirFuncFancy(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!A
         if (val.isGenericPoison()) {
             break :blk null;
         }
-        const alignment = try sema.validateAlignAllowZero(block, align_src, try val.toUnsignedIntSema(pt));
-        const default = target_util.defaultFunctionAlignment(target);
-        break :blk if (alignment == default) .none else alignment;
+        break :blk try sema.validateAlignAllowZero(block, align_src, try val.toUnsignedIntSema(pt));
     } else if (extra.data.bits.has_align_ref) blk: {
         const align_ref: Zir.Inst.Ref = @enumFromInt(sema.code.extra[extra_index]);
         extra_index += 1;
@@ -26592,9 +26590,7 @@ fn zirFuncFancy(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!A
             error.GenericPoison => break :blk null,
             else => |e| return e,
         };
-        const alignment = try sema.validateAlignAllowZero(block, align_src, try align_val.toUnsignedIntSema(pt));
-        const default = target_util.defaultFunctionAlignment(target);
-        break :blk if (alignment == default) .none else alignment;
+        break :blk try sema.validateAlignAllowZero(block, align_src, try align_val.toUnsignedIntSema(pt));
     } else .none;
 
     const @"addrspace": ?std.builtin.AddressSpace = if (extra.data.bits.has_addrspace_body) blk: {
diff --git a/src/Type.zig b/src/Type.zig
@@ -1020,7 +1020,7 @@ pub fn abiAlignmentInner(
             },
 
             // represents machine code; not a pointer
-            .func_type => return .{ .scalar = target_util.defaultFunctionAlignment(target) },
+            .func_type => return .{ .scalar = target_util.minFunctionAlignment(target) },
 
             .simple_type => |t| switch (t) {
                 .bool,
diff --git a/src/target.zig b/src/target.zig
@@ -459,7 +459,8 @@ pub fn llvmMachineAbi(target: std.Target) ?[:0]const u8 {
     }
 }
 
-/// This function returns 1 if function alignment is not observable or settable.
+/// This function returns 1 if function alignment is not observable or settable. Note that this
+/// value will not necessarily match the backend's default function alignment (e.g. for LLVM).
 pub fn defaultFunctionAlignment(target: std.Target) Alignment {
     // Overrides of the minimum for performance.
     return switch (target.cpu.arch) {