[X86] Enable LEA optimization pass by default

[aturetsk]

Summary

Enable LEA optimization pass by default.

[qcolombet]

lib/Target/X86/X86OptimizeLEAs.cpp

40

I would have been fine just replacing the cl::init by true :).

[aturetsk]

PR26575 was fixed in r260959.
I committed these changes again in r260979.

lib/Target/X86/X86OptimizeLEAs.cpp

 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetInstrInfo.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "x86-optimize-LEAs"
 
-static cl::opt<bool> EnableX86LEAOpt("enable-x86-lea-opt", cl::Hidden,
-                                     cl::desc("X86: Enable LEA optimizations."),
-                                     cl::init(false));
+static cl::opt<bool>
+    DisableX86LEAOpt("disable-x86-lea-opt", cl::Hidden,
+                     cl::desc("X86: Disable LEA optimizations."),
 
 STATISTIC(NumSubstLEAs, "Number of LEA instruction substitutions");
 STATISTIC(NumRedundantLEAs, "Number of redundant LEA instructions removed");
 
 class MemOpKey;
 
 /// \brief Returns a hash table key based on memory operands of \p MI. The
 /// number of the first memory operand of \p MI is specified through \p N.
bool OptimizeLEAPass::removeRedundantLEAs(MemOpMap &LEAs) {
 
   return Changed;
 }
 
 bool OptimizeLEAPass::runOnMachineFunction(MachineFunction &MF) {
   bool Changed = false;
 
   // Perform this optimization only if we care about code size.
-  if (!EnableX86LEAOpt || !MF.getFunction()->optForSize())
+  if (DisableX86LEAOpt || !MF.getFunction()->optForSize())
     return false;
 
   MRI = &MF.getRegInfo();
   TII = MF.getSubtarget<X86Subtarget>().getInstrInfo();
   TRI = MF.getSubtarget<X86Subtarget>().getRegisterInfo();
 
   // Process all basic blocks.
   for (auto &MBB : MF) {

test/CodeGen/X86/lea-opt.ll

-; RUN: llc < %s -mtriple=x86_64-linux -enable-x86-lea-opt | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-linux | FileCheck %s
 
 %struct.anon1 = type { i32, i32, i32 }
 %struct.anon2 = type { i32, [32 x i32], i32 }
 
 @arr1 = external global [65 x %struct.anon1], align 16
 @arr2 = external global [65 x %struct.anon2], align 16
 
 define void @test1(i64 %x) nounwind {