add a cl::opt override for TargetLoweringBase's JumpIsExpensive

This patch is not intended to change existing codegen behavior for any target. 
It just exposes the JumpIsExpensive setting on the command-line to allow for
easier testing and emergency overrides.

Also, change the existing regression test to use FileCheck, explicitly specify
the jump-is-expensive option, and use more precise checks.

Differential Revision: http://reviews.llvm.org/D10846

llvm-svn: 241179

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 53f3b00789c..78492a6e881 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -38,6 +38,11 @@
 #include <cctype>
 using namespace llvm;
 
+static cl::opt<bool> JumpIsExpensiveOverride(
+    "jump-is-expensive", cl::init(false),
+    cl::desc("Do not create extra branches to split comparison logic."),
+    cl::Hidden);
+
 /// InitLibcallNames - Set default libcall names.
 ///
 static void InitLibcallNames(const char **Names, const Triple &TT) {
@@ -757,7 +762,7 @@ TargetLoweringBase::TargetLoweringBase(const TargetMachine &tm) : TM(tm) {
   IntDivIsCheap = false;
   FsqrtIsCheap = false;
   Pow2SDivIsCheap = false;
-  JumpIsExpensive = false;
+  JumpIsExpensive = JumpIsExpensiveOverride;
   PredictableSelectIsExpensive = false;
   MaskAndBranchFoldingIsLegal = false;
   EnableExtLdPromotion = false;
@@ -915,6 +920,12 @@ bool TargetLoweringBase::canOpTrap(unsigned Op, EVT VT) const {
   }
 }
 
+void TargetLoweringBase::setJumpIsExpensive(bool isExpensive) {
+  // If the command-line option was specified, ignore this request.
+  if (!JumpIsExpensiveOverride.getNumOccurrences())
+    JumpIsExpensive = isExpensive;
+}
+
 TargetLoweringBase::LegalizeKind
 TargetLoweringBase::getTypeConversion(LLVMContext &Context, EVT VT) const {
   // If this is a simple type, use the ComputeRegisterProp mechanism.