[PATCH] D65937: [AArch64] Set pref. func. align to 8 bytes on Neoverse E1 & Cortex-A65

[Pablo Barrio via Phabricator via llvm-commits]

pbarrio created this revision.
pbarrio added reviewers: dmgreen, fhahn, samparker.
Herald added subscribers: hiraditya, kristof.beyls, javed.absar.
Herald added a project: LLVM.

The Arm Neoverse E1 and Cortex-A65 Software Optimization Guide [1][2],
Section "4.7 Branch instruction alignment" state:

"It is preferable for branch targets, including subroutine entry points,
to be placed on aligned 64-bit boundaries to maximize instruction fetch
efficiency."

This patch sets the preferred function alignment on Neoverse E1 and
Cortex-A65 to 2^3=8B. This was already the case in some Cortex-A CPUs
such as Cortex-A53.

[1] https://developer.arm.com/docs/swog466751/latest/arm-neoversetm-e1-core-software-optimization-guide
[2] https://developer.arm.com/docs/swog010045/latest/arm-cortex-a65-core-software-optimization-guide


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65937

Files:
  llvm/lib/Target/AArch64/AArch64Subtarget.cpp
  llvm/test/CodeGen/AArch64/preferred-function-alignment.ll


Index: llvm/test/CodeGen/AArch64/preferred-function-alignment.ll
===================================================================
--- llvm/test/CodeGen/AArch64/preferred-function-alignment.ll
+++ llvm/test/CodeGen/AArch64/preferred-function-alignment.ll
@@ -2,6 +2,8 @@
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a35 < %s | FileCheck --check-prefixes=ALIGN2,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a53 < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a57 < %s | FileCheck --check-prefixes=ALIGN4,CHECK %s
+; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a65 < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
+; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a65ae < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a72 < %s | FileCheck --check-prefixes=ALIGN4,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a73 < %s | FileCheck --check-prefixes=ALIGN4,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cortex-a75 < %s | FileCheck --check-prefixes=ALIGN4,CHECK %s
@@ -9,6 +11,7 @@
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=cyclone < %s | FileCheck --check-prefixes=ALIGN2,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=falkor < %s | FileCheck --check-prefixes=ALIGN2,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=kryo < %s | FileCheck --check-prefixes=ALIGN2,CHECK %s
+; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=neoverse-e1 < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=neoverse-n1 < %s | FileCheck --check-prefixes=ALIGN4,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=thunderx < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
 ; RUN: llc -mtriple=aarch64-unknown-linux -mcpu=thunderxt81 < %s | FileCheck --check-prefixes=ALIGN3,CHECK %s
Index: llvm/lib/Target/AArch64/AArch64Subtarget.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64Subtarget.cpp
+++ llvm/lib/Target/AArch64/AArch64Subtarget.cpp
@@ -80,6 +80,7 @@
     PrefFunctionAlignment = 4;
     break;
   case CortexA65:
+    PrefFunctionAlignment = 3;
     break;
   case CortexA72:
   case CortexA73:
@@ -125,6 +126,7 @@
     MinVectorRegisterBitWidth = 128;
     break;
   case NeoverseE1:
+    PrefFunctionAlignment = 3;
     break;
   case NeoverseN1:
     PrefFunctionAlignment = 4;


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