[llvm] 9878ef3 - CodeGen: Respect function align attribute if less than preferred alignment.

[via llvm-commits]

Author: Peter Collingbourne
Date: 2025-07-18T13:33:46-07:00
New Revision: 9878ef3abd2a48fcfb81357d581dac292b52ddb3

URL: https://github.com/llvm/llvm-project/commit/9878ef3abd2a48fcfb81357d581dac292b52ddb3
DIFF: https://github.com/llvm/llvm-project/commit/9878ef3abd2a48fcfb81357d581dac292b52ddb3.diff

LOG: CodeGen: Respect function align attribute if less than preferred alignment.



Reviewers: arsenm, efriedma-quic

Reviewed By: arsenm

Pull Request: https://github.com/llvm/llvm-project/pull/149444

Added: 
    llvm/test/CodeGen/X86/function-align.ll

Modified: 
    llvm/lib/CodeGen/MachineFunction.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index 38ad582ba923c..429a17a9113d3 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -211,9 +211,8 @@ void MachineFunction::init() {
   ConstantPool = new (Allocator) MachineConstantPool(getDataLayout());
   Alignment = STI->getTargetLowering()->getMinFunctionAlignment();
 
-  // FIXME: Shouldn't use pref alignment if explicit alignment is set on F.
   // FIXME: Use Function::hasOptSize().
-  if (!F.hasFnAttribute(Attribute::OptimizeForSize))
+  if (!F.getAlign() && !F.hasFnAttribute(Attribute::OptimizeForSize))
     Alignment = std::max(Alignment,
                          STI->getTargetLowering()->getPrefFunctionAlignment());
 

diff  --git a/llvm/test/CodeGen/X86/function-align.ll b/llvm/test/CodeGen/X86/function-align.ll
new file mode 100644
index 0000000000000..11d0e99929927
--- /dev/null
+++ b/llvm/test/CodeGen/X86/function-align.ll
@@ -0,0 +1,18 @@
+; RUN: llc -function-sections < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: .section .text.f1
+; CHECK-NOT: .p2align
+; CHECK: f1:
+define void @f1() align 1 {
+  ret void
+}
+
+; CHECK: .section .text.f2
+; CHECK-NEXT: .globl f2
+; CHECK-NEXT: .p2align 1
+define void @f2() align 2 {
+  ret void
+}