Make the 'shrink global to bool' optimization more self contained, and thus
easier to show that its safe. No functionality change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45946 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index c3c0530..4b01750 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1257,9 +1257,28 @@
return false;
}
-/// ShrinkGlobalToBoolean - At this point, we have learned that the only two
-/// values ever stored into GV are its initializer and OtherVal.
-static void ShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
+/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
+/// two values ever stored into GV are its initializer and OtherVal. See if we
+/// can shrink the global into a boolean and select between the two values
+/// whenever it is used. This exposes the values to other scalar optimizations.
+static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
+ const Type *GVElType = GV->getType()->getElementType();
+
+ // If GVElType is already i1, it is already shrunk. If the type of the GV is
+ // an FP value or vector, don't do this optimization because a select between
+ // them is very expensive and unlikely to lead to later simplification.
+ if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
+ isa<VectorType>(GVElType))
+ return false;
+
+ // Walk the use list of the global seeing if all the uses are load or store.
+ // If there is anything else, bail out.
+ for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
+ if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
+ return false;
+
+ DOUT << " *** SHRINKING TO BOOL: " << *GV;
+
// Create the new global, initializing it to false.
GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
GlobalValue::InternalLinkage, ConstantInt::getFalse(),
@@ -1307,7 +1326,7 @@
}
}
new StoreInst(StoreVal, NewGV, SI);
- } else if (!UI->use_empty()) {
+ } else {
// Change the load into a load of bool then a select.
LoadInst *LI = cast<LoadInst>(UI);
LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
@@ -1323,6 +1342,7 @@
}
GV->eraseFromParent();
+ return true;
}
@@ -1464,12 +1484,7 @@
// Otherwise, if the global was not a boolean, we can shrink it to be a
// boolean.
if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
- if (GV->getType()->getElementType() != Type::Int1Ty &&
- !GV->getType()->getElementType()->isFloatingPoint() &&
- !isa<VectorType>(GV->getType()->getElementType()) &&
- !GS.HasPHIUser && !GS.isNotSuitableForSRA) {
- DOUT << " *** SHRINKING TO BOOL: " << *GV;
- ShrinkGlobalToBoolean(GV, SOVConstant);
+ if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
++NumShrunkToBool;
return true;
}