[CodeGen] Add -align-loops

to `lib/CodeGen/CommandFlags.cpp`. It can replace
-x86-experimental-pref-loop-alignment=.

The loop alignment is only used by MachineBlockPlacement.
The implementation uses a new `llvm::TargetOptions` for now, as
an IR function attribute/module flags metadata may be overkill.

This is the llvm part of D106701.

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 842280a..cfbbba6 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -52,6 +52,7 @@
 #include "llvm/Support/MachineValueType.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/Utils/SizeOpts.h"
 #include <algorithm>
 #include <cassert>
@@ -2018,6 +2019,12 @@ bool TargetLoweringBase::isJumpTableRelative() const {
   return getTargetMachine().isPositionIndependent();
 }
 
+Align TargetLoweringBase::getPrefLoopAlignment(MachineLoop *ML) const {
+  if (TM.Options.LoopAlignment)
+    return Align(TM.Options.LoopAlignment);
+  return PrefLoopAlignment;
+}
+
 //===----------------------------------------------------------------------===//
 //  Reciprocal Estimates
 //===----------------------------------------------------------------------===//