[NewGVN] Add command-line option to control the generation of phi-of-ops (disable by default)

[mcrosier]

Summary

Useful for testing and debugging. Disabled by default, per Danny's request.

[• dberlin]

I think where i come down on this is: disabled by default , and modify the existing test arguments to enable it, so that you don't have to xfail or modify a ton of tests :)
(then when it's fixed we can just remove the test arguments again).
But i'm also not opposed to doing the test updating.

[mcrosier]

-Disable this feature by default.
-Update test RUN commands due to change.

[mcrosier]

r310594

lib/Transforms/Scalar/NewGVN.cpp

 static cl::opt<bool> EnableStoreRefinement("enable-store-refinement",
                                            cl::init(false), cl::Hidden);
 
+/// Currently, the generation "phi of ops" can result in correctness issues.
+static cl::opt<bool> EnablePhiOfOps("enable-phi-of-ops", cl::init(false),
+                                    cl::Hidden);
+
 //===----------------------------------------------------------------------===//
 //                                GVN Pass
 //===----------------------------------------------------------------------===//

 }
 
 static bool okayForPHIOfOps(const Instruction *I) {
+  if (!EnablePhiOfOps)
+    return false;
   return isa<BinaryOperator>(I) || isa<SelectInst>(I) || isa<CmpInst>(I) ||
          isa<LoadInst>(I);
 }

test/Transforms/NewGVN/completeness.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -basicaa -newgvn -S | FileCheck %s
+; RUN: opt < %s -basicaa -newgvn -enable-phi-of-ops=true -S | FileCheck %s
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 define i32 @test1(i32, i8**) {

test/Transforms/NewGVN/pr33461.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ;; Ensure the store verifier is not overzealous
-; RUN: opt -newgvn -S %s | FileCheck %s
+; RUN: opt -newgvn -enable-phi-of-ops=true -S %s | FileCheck %s
 @b = external global i16, align 2
 
 define void @patatino() {

test/Transforms/NewGVN/storeoverstore.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -newgvn -S < %s | FileCheck %s
-; RUN: opt -passes=newgvn -S -o - %s | FileCheck %s
+; RUN: opt -newgvn -enable-phi-of-ops=true -S < %s | FileCheck %s
+; RUN: opt -passes=newgvn -enable-phi-of-ops=true -S -o - %s | FileCheck %s
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"