Move zext and sext casts fed by loads into the same block as the
load, to help SelectionDAG fold them into the loads, unless
conditions are unfavorable.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84271 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index a3e3fea..42209b8c 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -73,6 +73,7 @@
DenseMap<Value*,Value*> &SunkAddrs);
bool OptimizeInlineAsmInst(Instruction *I, CallSite CS,
DenseMap<Value*,Value*> &SunkAddrs);
+ bool MoveExtToFormExtLoad(Instruction *I);
bool OptimizeExtUses(Instruction *I);
void findLoopBackEdges(const Function &F);
};
@@ -731,6 +732,43 @@
return MadeChange;
}
+/// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
+/// basic block as the load, unless conditions are unfavorable. This allows
+/// SelectionDAG to fold the extend into the load.
+///
+bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
+ // Look for a load being extended.
+ LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
+ if (!LI) return false;
+
+ // If they're already in the same block, there's nothing to do.
+ if (LI->getParent() == I->getParent())
+ return false;
+
+ // If the load has other users and the truncate is not free, this probably
+ // isn't worthwhile.
+ if (!LI->hasOneUse() &&
+ TLI && !TLI->isTruncateFree(I->getType(), LI->getType()))
+ return false;
+
+ // Check whether the target supports casts folded into loads.
+ unsigned LType;
+ if (isa<ZExtInst>(I))
+ LType = ISD::ZEXTLOAD;
+ else {
+ assert(isa<SExtInst>(I) && "Unexpected ext type!");
+ LType = ISD::SEXTLOAD;
+ }
+ if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
+ return false;
+
+ // Move the extend into the same block as the load, so that SelectionDAG
+ // can fold it.
+ I->removeFromParent();
+ I->insertAfter(LI);
+ return true;
+}
+
bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
BasicBlock *DefBB = I->getParent();
@@ -846,8 +884,10 @@
MadeChange |= Change;
}
- if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I)))
+ if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I))) {
+ MadeChange |= MoveExtToFormExtLoad(I);
MadeChange |= OptimizeExtUses(I);
+ }
} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
MadeChange |= OptimizeCmpExpression(CI);
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {