[RISCV] Add tune features of preferred function/loop align

D144048 has added preferred function and loop alignment to
RISCVSubtarget, but now we need to set them manually for
different processors.

Tune features that set preferred function/loop align to
[2, 64] bytes (align 1 is not here since the min align is 2)
are added. These features can be used in processor
definitions.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D157832

Author: wangpc-pp

llvm/lib/Target/RISCV/RISCVFeatures.td

@@ -925,3 +925,12 @@ def FeatureTaggedGlobals : SubtargetFeature<"tagged-globals",
     "AllowTaggedGlobals",
     "true", "Use an instruction sequence for taking the address of a global "
     "that allows a memory tag in the upper address bits">;
+
+foreach align = [2, 4, 8, 16, 32, 64] in {
+  def TunePrefFunctionAlignment # align :
+      SubtargetFeature<"pref-func-align-" # align, "PrefFunctionAlignment",
+                       "Align(" # align # ")", "Set preferred function alignment to " # align # " bytes">;
+  def TunePrefLoopAlignment # align :
+      SubtargetFeature<"pref-loop-align-" # align, "PrefLoopAlignment",
+                       "Align(" # align # ")", "Set preferred loop alignment to " # align # " bytes">;
+}

llvm/test/CodeGen/RISCV/align-loops.ll

@@ -1,6 +1,8 @@
 ; RUN: llc < %s -mtriple=riscv64 | FileCheck %s
 ; RUN: llc < %s -mtriple=riscv64 -align-loops=16 | FileCheck %s -check-prefix=ALIGN_16
 ; RUN: llc < %s -mtriple=riscv64 -align-loops=32 | FileCheck %s -check-prefix=ALIGN_32
+; RUN: llc < %s -mtriple=riscv64 -mattr=+pref-loop-align-16 | FileCheck %s -check-prefix=ALIGN_16
+; RUN: llc < %s -mtriple=riscv64 -mattr=+pref-loop-align-32 | FileCheck %s -check-prefix=ALIGN_32
 
 declare void @foo()
 

llvm/test/CodeGen/RISCV/align.ll

@@ -2,6 +2,8 @@
 ; RUN:   | FileCheck %s -check-prefix=RV32I
 ; RUN: llc -mtriple=riscv32 -mattr=+c -verify-machineinstrs < %s \
 ; RUN:   | FileCheck %s -check-prefix=RV32C
+; RUN: llc -mtriple=riscv32 -mattr=+pref-func-align-32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck %s -check-prefix=ALIGN-32
 ; RUN: llc -filetype=obj -mtriple=riscv32 < %s -o %t
 ; RUN: llvm-readelf -S %t | FileCheck %s --check-prefixes=SEC,SEC-I
 ; RUN: llc -filetype=obj -mtriple=riscv32 -mattr=+c < %s -o %t
@@ -16,6 +18,8 @@ define void @foo() {
 ;RV32I: foo:
 ;RV32C: .p2align 1
 ;RV32C: foo:
+;ALIGN-32: .p2align 5
+;ALIGN-32: foo:
 entry:
   ret void
 }