diff options
| -rw-r--r-- | lib/Transforms/IPO/GlobalOpt.cpp | 50 | ||||
| -rw-r--r-- | test/Transforms/GlobalOpt/2009-01-13-phi-user.ll | 35 |
2 files changed, 61 insertions, 24 deletions
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp index 53aa03d..b4a5634 100644 --- a/lib/Transforms/IPO/GlobalOpt.cpp +++ b/lib/Transforms/IPO/GlobalOpt.cpp @@ -733,44 +733,46 @@ static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { /// if the loaded value is dynamically null, then we know that they cannot be /// reachable with a null optimize away the load. static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { - std::vector<LoadInst*> Loads; bool Changed = false; + // Keep track of whether we are able to remove all the uses of the global + // other than the store that defines it. + bool AllNonStoreUsesGone = true; + // Replace all uses of loads with uses of uses of the stored value. - for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); - GUI != E; ++GUI) - if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { - Loads.push_back(LI); + for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){ + User *GlobalUser = *GUI++; + if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) { Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); + // If we were able to delete all uses of the loads + if (LI->use_empty()) { + LI->eraseFromParent(); + Changed = true; + } else { + AllNonStoreUsesGone = false; + } + } else if (isa<StoreInst>(GlobalUser)) { + // Ignore the store that stores "LV" to the global. + assert(GlobalUser->getOperand(1) == GV && + "Must be storing *to* the global"); } else { - // If we get here we could have stores, selects, or phi nodes whose values - // are loaded. - assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || - isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && - "Only expect load and stores!"); + AllNonStoreUsesGone = false; + + // If we get here we could have other crazy uses that are transitively + // loaded. + assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) || + isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!"); } + } if (Changed) { DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; ++NumGlobUses; } - // Delete all of the loads we can, keeping track of whether we nuked them all! - bool AllLoadsGone = true; - while (!Loads.empty()) { - LoadInst *L = Loads.back(); - if (L->use_empty()) { - L->eraseFromParent(); - Changed = true; - } else { - AllLoadsGone = false; - } - Loads.pop_back(); - } - // If we nuked all of the loads, then none of the stores are needed either, // nor is the global. - if (AllLoadsGone) { + if (AllNonStoreUsesGone) { DOUT << " *** GLOBAL NOW DEAD!\n"; CleanupConstantGlobalUsers(GV, 0); if (GV->use_empty()) { diff --git a/test/Transforms/GlobalOpt/2009-01-13-phi-user.ll b/test/Transforms/GlobalOpt/2009-01-13-phi-user.ll new file mode 100644 index 0000000..03ec3b6 --- /dev/null +++ b/test/Transforms/GlobalOpt/2009-01-13-phi-user.ll @@ -0,0 +1,35 @@ +; RUN: llvm-as < %s | opt -globalopt | llvm-dis | grep {phi.*@head} +; PR3321 +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128" +target triple = "x86_64-unknown-linux-gnu" + %struct.node = type { %struct.node*, i32 } +@head = internal global %struct.node* null ; <%struct.node**> [#uses=2] +@node = internal global %struct.node { %struct.node* null, i32 42 }, align 16 ; <%struct.node*> [#uses=1] + +define i32 @f() nounwind { +entry: + store %struct.node* @node, %struct.node** @head, align 8 + br label %bb1 + +bb: ; preds = %bb1 + %0 = getelementptr %struct.node* %t.0, i64 0, i32 1 ; <i32*> [#uses=1] + %1 = load i32* %0, align 4 ; <i32> [#uses=1] + %2 = getelementptr %struct.node* %t.0, i64 0, i32 0 ; <%struct.node**> [#uses=1] + br label %bb1 + +bb1: ; preds = %bb, %entry + %value.0 = phi i32 [ undef, %entry ], [ %1, %bb ] ; <i32> [#uses=1] + %t.0.in = phi %struct.node** [ @head, %entry ], [ %2, %bb ] ; <%struct.node**> [#uses=1] + %t.0 = load %struct.node** %t.0.in ; <%struct.node*> [#uses=3] + %3 = icmp eq %struct.node* %t.0, null ; <i1> [#uses=1] + br i1 %3, label %bb2, label %bb + +bb2: ; preds = %bb1 + ret i32 %value.0 +} + +define i32 @main() nounwind { +entry: + %0 = call i32 @f() nounwind ; <i32> [#uses=1] + ret i32 %0 +} |