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

Reviewers: arsenm, efriedma-quic

Reviewed By: arsenm

Pull Request: #149444

Author: pcc

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());
 

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
+}