[AArch64] Enable AArch64 loop idiom transform pass (#77480)

Following on from

llvm/llvm-project#72273

which added the new AArch64 loop idiom transformation pass, this patch
enables the pass by default for AArch64.

Author: david-arm

llvm/lib/Target/AArch64/AArch64LoopIdiomTransform.cpp

@@ -53,7 +53,7 @@ using namespace PatternMatch;
 #define DEBUG_TYPE "aarch64-loop-idiom-transform"
 
 static cl::opt<bool>
-    DisableAll("disable-aarch64-lit-all", cl::Hidden, cl::init(true),
+    DisableAll("disable-aarch64-lit-all", cl::Hidden, cl::init(false),
                cl::desc("Disable AArch64 Loop Idiom Transform Pass."));
 
 static cl::opt<bool> DisableByteCmp(

llvm/test/Transforms/LoopIdiom/AArch64/byte-compare-index.ll

@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
-; RUN: opt -aarch64-lit -disable-aarch64-lit-all=false -aarch64-lit-verify -verify-dom-info -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s
-; RUN: opt -aarch64-lit -disable-aarch64-lit-all=false -simplifycfg -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=LOOP-DEL
-; RUN: opt -aarch64-lit -disable-aarch64-lit-all=false -mtriple aarch64-unknown-linux-gnu -S < %s | FileCheck %s --check-prefix=NO-TRANSFORM
+; RUN: opt -aarch64-lit -aarch64-lit-verify -verify-dom-info -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s
+; RUN: opt -aarch64-lit -simplifycfg -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=LOOP-DEL
+; RUN: opt -aarch64-lit -mtriple aarch64-unknown-linux-gnu -S < %s | FileCheck %s --check-prefix=NO-TRANSFORM
 
 define i32 @compare_bytes_simple(ptr %a, ptr %b, i32 %len, i32 %extra, i32 %n) {
 ; CHECK-LABEL: define i32 @compare_bytes_simple(