[x86] add debug option for and-immediate shrinking

  
The commit that added this functionality:
rL322957

may be causing/exposing a miscompile in PR38648:
https://bugs.llvm.org/show_bug.cgi?id=38648

so allow enabling/disabling to make debugging easier.

llvm-svn: 340540

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 7236fdeb8be..1cca1f1e14b 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -41,6 +41,10 @@ using namespace llvm;
 
 STATISTIC(NumLoadMoved, "Number of loads moved below TokenFactor");
 
+static cl::opt<bool> AndImmShrink("x86-and-imm-shrink", cl::init(true),
+    cl::desc("Enable setting constant bits to reduce size of mask immediates"),
+    cl::Hidden);
+
 //===----------------------------------------------------------------------===//
 //                      Pattern Matcher Implementation
 //===----------------------------------------------------------------------===//
@@ -2927,7 +2931,7 @@ void X86DAGToDAGISel::Select(SDNode *Node) {
   case ISD::AND:
     if (matchBEXTRFromAnd(Node))
       return;
-    if (shrinkAndImmediate(Node))
+    if (AndImmShrink && shrinkAndImmediate(Node))
       return;
 
     LLVM_FALLTHROUGH;