[AArch64] Add option to enable/disable load-store renaming.

This patch adds a new option to enable/disable register renaming in the
load-store optimizer. Defaults to disabled, as there is a potential
mis-compile caused by this.

Author: fhahn

llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp

@@ -66,6 +66,10 @@ static cl::opt<unsigned> LdStLimit("aarch64-load-store-scan-limit",
 static cl::opt<unsigned> UpdateLimit("aarch64-update-scan-limit", cl::init(100),
                                      cl::Hidden);
 
+// Enable register renaming to find additional store pairing opportunities.
+static cl::opt<bool> EnableRenaming("aarch64-load-store-renaming",
+                                    cl::init(false), cl::Hidden);
+
 #define AARCH64_LOAD_STORE_OPT_NAME "AArch64 load / store optimization pass"
 
 namespace {
@@ -1446,6 +1450,9 @@ AArch64LoadStoreOpt::findMatchingInsn(MachineBasicBlock::iterator I,
   bool IsPromotableZeroStore = isPromotableZeroStoreInst(FirstMI);
 
   Optional<bool> MaybeCanRename = None;
+  if (!EnableRenaming)
+    MaybeCanRename = {false};
+
   SmallPtrSet<const TargetRegisterClass *, 5> RequiredClasses;
   LiveRegUnits UsedInBetween;
   UsedInBetween.init(*TRI);

llvm/test/CodeGen/AArch64/arm64-abi-varargs.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=arm64-apple-ios7.0.0 -mcpu=cyclone -enable-misched=false | FileCheck %s
+; RUN: llc -aarch64-load-store-renaming=true < %s -mtriple=arm64-apple-ios7.0.0 -mcpu=cyclone -enable-misched=false | FileCheck %s
 
 ; rdar://13625505
 ; Here we have 9 fixed integer arguments the 9th argument in on stack, the

llvm/test/CodeGen/AArch64/arm64-abi_align.ll

@@ -1,5 +1,5 @@
-; RUN: llc -fast-isel-sink-local-values < %s -mtriple=arm64-apple-darwin -mcpu=cyclone -enable-misched=false -frame-pointer=all | FileCheck %s
-; RUN: llc -fast-isel-sink-local-values < %s -mtriple=arm64-apple-darwin -O0 -frame-pointer=all -fast-isel | FileCheck -check-prefix=FAST %s
+; RUN: llc -fast-isel-sink-local-values -aarch64-load-store-renaming=true < %s -mtriple=arm64-apple-darwin -mcpu=cyclone -enable-misched=false -frame-pointer=all | FileCheck %s
+; RUN: llc -fast-isel-sink-local-values -aarch64-load-store-renaming=true  < %s -mtriple=arm64-apple-darwin -O0 -frame-pointer=all -fast-isel | FileCheck -check-prefix=FAST %s
 
 ; rdar://12648441
 ; Generated from arm64-arguments.c with -O2.

llvm/test/CodeGen/AArch64/arm64-variadic-aapcs.ll

@@ -1,4 +1,4 @@
-; RUN: llc -verify-machineinstrs -mtriple=arm64-linux-gnu -pre-RA-sched=linearize -enable-misched=false -disable-post-ra < %s | FileCheck %s
+; RUN: llc -aarch64-load-store-renaming=true -verify-machineinstrs -mtriple=arm64-linux-gnu -pre-RA-sched=linearize -enable-misched=false -disable-post-ra < %s | FileCheck %s
 
 %va_list = type {i8*, i8*, i8*, i32, i32}
 

llvm/test/CodeGen/AArch64/machine-outliner-remarks.ll

@@ -4,7 +4,7 @@
 ; CHECK-SAME: Bytes from outlining all occurrences (16) >=
 ; CHECK-SAME: Unoutlined instruction bytes (16)
 ; CHECK-SAME: (Also found at: <UNKNOWN LOCATION>)
-; CHECK: remark: <unknown>:0:0: Saved 36 bytes by outlining 11 instructions
+; CHECK: remark: <unknown>:0:0: Saved 48 bytes by outlining 14 instructions
 ; CHECK-SAME: from 2 locations. (Found at: <UNKNOWN LOCATION>,
 ; CHECK-SAME: <UNKNOWN LOCATION>)
 ; RUN: llc %s -enable-machine-outliner -mtriple=aarch64-unknown-unknown -o /dev/null -pass-remarks-missed=machine-outliner -pass-remarks-output=%t.yaml
@@ -38,10 +38,10 @@
 ; YAML-NEXT: Function:        OUTLINED_FUNCTION_0
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          'Saved '
-; YAML-NEXT:   - OutliningBenefit: '36'
+; YAML-NEXT:   - OutliningBenefit: '48'
 ; YAML-NEXT:   - String:          ' bytes by '
 ; YAML-NEXT:   - String:          'outlining '
-; YAML-NEXT:   - Length:          '11'
+; YAML-NEXT:   - Length:          '14'
 ; YAML-NEXT:   - String:          ' instructions '
 ; YAML-NEXT:   - String:          'from '
 ; YAML-NEXT:   - NumOccurrences:  '2'

llvm/test/CodeGen/AArch64/machine-outliner.ll

@@ -1,5 +1,5 @@
-; RUN: llc -verify-machineinstrs -enable-machine-outliner -mtriple=aarch64-apple-darwin < %s | FileCheck %s
-; RUN: llc -verify-machineinstrs -enable-machine-outliner -mtriple=aarch64-apple-darwin -mcpu=cortex-a53 -enable-misched=false < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs -enable-machine-outliner -aarch64-load-store-renaming=true -mtriple=aarch64-apple-darwin < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs -enable-machine-outliner -aarch64-load-store-renaming=true -mtriple=aarch64-apple-darwin -mcpu=cortex-a53 -enable-misched=false < %s | FileCheck %s
 ; RUN: llc -verify-machineinstrs -enable-machine-outliner -enable-linkonceodr-outlining -mtriple=aarch64-apple-darwin < %s | FileCheck %s -check-prefix=ODR
 ; RUN: llc -verify-machineinstrs -enable-machine-outliner -mtriple=aarch64-apple-darwin -stop-after=machine-outliner < %s | FileCheck %s -check-prefix=TARGET_FEATURES
 

llvm/test/CodeGen/AArch64/stp-opt-with-renaming-debug.mir

@@ -1,4 +1,4 @@
-# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -verify-machineinstrs -o - %s | FileCheck %s
+# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -aarch64-load-store-renaming=true -verify-machineinstrs -o - %s | FileCheck %s
 --- |
   define void @test_dbg_value1() #0 { ret void }
   define void @test_dbg_value2() #0 { ret void }

llvm/test/CodeGen/AArch64/stp-opt-with-renaming-reserved-regs.mir

@@ -1,9 +1,9 @@
-# RUN: llc -run-pass=aarch64-ldst-opt -mattr=+reserve-x10 -mattr=+reserve-x11 \
-# RUN:     -mattr=+reserve-x15 -mtriple=arm64-apple-iphoneos -verify-machineinstrs \
+# RUN: llc -run-pass=aarch64-ldst-opt -aarch64-load-store-renaming=true -mattr=+reserve-x10 \
+# RUN:     -mattr=+reserve-x11 -mattr=+reserve-x15 -mtriple=arm64-apple-iphoneos -verify-machineinstrs \
 # RUN:     -o - %s | FileCheck --check-prefix=CHECK --check-prefix=PRESERVED %s
 
-# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -verify-machineinstrs \
-# RUN:     -o - %s | FileCheck --check-prefix=CHECK --check-prefix=NOPRES %s
+# RUN: llc -run-pass=aarch64-ldst-opt -aarch64-load-store-renaming=true -mtriple=arm64-apple-iphoneos \
+# RUN:     -verify-machineinstrs -o - %s | FileCheck --check-prefix=CHECK --check-prefix=NOPRES %s
 
 
 # Make sure we do not pick reserved registers. For test1, we would pick x10,

llvm/test/CodeGen/AArch64/stp-opt-with-renaming.mir

@@ -1,5 +1,11 @@
-# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -verify-machineinstrs -o - %s | FileCheck %s
+# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -verify-machineinstrs -aarch64-load-store-renaming=true -o - %s | FileCheck %s
+# RUN: llc -run-pass=aarch64-ldst-opt -mtriple=arm64-apple-iphoneos -verify-machineinstrs -o - %s | FileCheck --check-prefix=NO-RENAME %s
 
+# NO-RENAME-NOT: STP
+# NO-RENAME:     test12
+# NO-RENAME:     STP
+# NO-RENAME-NOT: STP
+#
 ---
 # CHECK-LABEL: name: test1
 # CHECK: bb.0: