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CodeGen: Emit .prefalign directives based on the prefalign attribute. #155529

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CodeGen: Emit .prefalign directives based on the prefalign attribute. #155529

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bbf59ae
[𝘀𝗽𝗿] initial version
pcc Aug 27, 2025
38615b9
Fix failing lld test
pcc Aug 27, 2025
64ff4bc
Address review comment
pcc Aug 27, 2025
7e7c37e
Split out #158368
pcc Sep 12, 2025
f5074c5
Rebase
pcc Oct 6, 2025
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2 changes: 1 addition & 1 deletion lld/test/ELF/lto/linker-script-symbols-ipo.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@
; NOIPO: <foo>:
; NOIPO-NEXT: movl $2, %eax
; NOIPO: <_start>:
; NOIPO-NEXT: jmp 0x201160 <foo>
; NOIPO-NEXT: jmp 0x201158 <foo>

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
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16 changes: 14 additions & 2 deletions llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -977,8 +977,20 @@ void AsmPrinter::emitFunctionHeader() {
emitVisibility(CurrentFnSym, F.getVisibility());

emitLinkage(&F, CurrentFnSym);
if (MAI->hasFunctionAlignment())
emitAlignment(MF->getPreferredAlignment(), &F);
if (MAI->hasFunctionAlignment()) {
// The preferred alignment directive will not have the intended effect
// unless function sections are enabled.
if (MAI->useIntegratedAssembler() && MAI->hasPreferredAlignment() &&
TM.getFunctionSections()) {
Align Alignment = MF->getAlignment();
Align PrefAlignment = MF->getPreferredAlignment();
emitAlignment(Alignment, &F);
if (Alignment != PrefAlignment)
OutStreamer->emitPrefAlign(PrefAlignment);
} else {
emitAlignment(MF->getPreferredAlignment(), &F);
}
}

if (MAI->hasDotTypeDotSizeDirective())
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_ELF_TypeFunction);
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27 changes: 27 additions & 0 deletions llvm/test/CodeGen/X86/prefalign.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
; RUN: llc < %s | FileCheck --check-prefixes=CHECK,NOFS %s
; RUN: llc -function-sections < %s | FileCheck --check-prefixes=CHECK,FS %s

target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; CHECK: .globl f1
; NOFS-NEXT: .p2align 4
; FS-NEXT: .prefalign 16
define void @f1() {
ret void
}

; CHECK: .globl f2
; CHECK-NOT: .prefalign
; CHECK-NOT: .p2align
define void @f2() prefalign 1 {
ret void
}

; CHECK: .globl f3
; NOFS-NEXT: .p2align 2
; FS-NEXT: .p2align 1
; FS-NEXT: .prefalign 4
define void @f3() align 2 prefalign 4 {
ret void
}
4 changes: 2 additions & 2 deletions llvm/test/Transforms/SampleProfile/pseudo-probe-emit.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -127,7 +127,7 @@ entry:
; CHECK-SEC-ELF: [Nr] Name Type {{.*}} ES Flg Lk Inf Al
; CHECK-SEC-ELF: [ 3] .text.foo PROGBITS {{.*}} 00 AX 0 0 16
; CHECK-SEC-ELF: [ 5] .text.foo2 PROGBITS {{.*}} 00 AX 0 0 16
; CHECK-SEC-ELF: [ 8] .text.foo3 PROGBITS {{.*}} 00 AXG 0 0 16
; CHECK-SEC-ELF: [ 8] .text.foo3 PROGBITS {{.*}} 00 AXG 0 0 1
; CHECK-SEC-ELF-COUNT-3: .pseudo_probe_desc PROGBITS
; CHECK-SEC-ELF: .pseudo_probe PROGBITS {{.*}} 00 L 3 0 1
; CHECK-SEC-ELF-NEXT: .pseudo_probe PROGBITS {{.*}} 00 L 5 0 1
Expand All @@ -154,7 +154,7 @@ entry:
; CHECK-SEC2-ELF: [Nr] Name Type {{.*}} ES Flg Lk Inf Al
; CHECK-SEC2-ELF: [ 3] .text PROGBITS {{.*}} 00 AX 0 0 16
; CHECK-SEC2-ELF: [ 5] .text PROGBITS {{.*}} 00 AX 0 0 16
; CHECK-SEC2-ELF: [ 8] .text PROGBITS {{.*}} 00 AXG 0 0 16
; CHECK-SEC2-ELF: [ 8] .text PROGBITS {{.*}} 00 AXG 0 0 1
; CHECK-SEC2-ELF-COUNT-3: .pseudo_probe_desc PROGBITS
; CHECK-SEC2-ELF: .pseudo_probe PROGBITS {{.*}} 00 L 3 0 1
; CHECK-SEC2-ELF-NEXT: .pseudo_probe PROGBITS {{.*}} 00 L 5 0 1
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