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CodeGen: Respect function align attribute if less than preferred alignment. #149444

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CodeGen: Respect function align attribute if less than preferred alignment. #149444

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3 changes: 1 addition & 2 deletions llvm/lib/CodeGen/MachineFunction.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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))
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This will also disrespect getMinFunctionAlignment which is probably more of a problem

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Applying this in the function constructor also seems like the wrong place to do this

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I don't see why it doesn't respect getMinFunctionAlignment. getMinFunctionAlignment is read on line 212 and combined with the preferred alignment with std::max here, so the result will be at least getMinFunctionAlignment.

Alignment = std::max(Alignment,
STI->getTargetLowering()->getPrefFunctionAlignment());

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18 changes: 18 additions & 0 deletions llvm/test/CodeGen/X86/function-align.ll
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@@ -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
}
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