1 files changed, 70 insertions, 0 deletions
diff --git a/llvm/pass/CombineZExtTrunc.cpp b/llvm/pass/CombineZExtTrunc.cpp
new file mode 100644
index 0000000..de9a87f
--- /dev/null
+++ b/llvm/pass/CombineZExtTrunc.cpp
@@ -0,0 +1,70 @@
+/*
+ *  (C) 2015 by Computer System Laboratory, IIS, Academia Sinica, Taiwan.
+ *      See COPYRIGHT in top-level directory.
+ */
+
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm-target.h"
+#include "llvm-opc.h"
+#include "llvm-pass.h"
+#include "utils.h"
+
+#define PASS_NAME "CombineZExtTrunc"
+
+/*
+ * CombineZExtTrunc Pass
+ */
+class CombineZExtTrunc : public FunctionPass {
+public:
+    static char ID;
+    explicit CombineZExtTrunc() : FunctionPass(ID) {}
+    bool runOnFunction(Function &F);
+};
+
+char CombineZExtTrunc::ID = 0;
+INITIALIZE_PASS(CombineZExtTrunc, "combinezet",
+        "Combine ZExt followed by Trunc", false, false)
+
+FunctionPass *llvm::createCombineZExtTrunc()
+{
+    return new CombineZExtTrunc;
+}
+
+bool CombineZExtTrunc::runOnFunction(Function &F)
+{
+    bool Changed = false;
+    IVec toErase;
+
+    SmallVector<Instruction*, 4> Worklist;
+    for (auto II = inst_begin(F), EE = inst_end(F); II != EE; II++) {
+        Instruction *I = &*II;
+        if (isa<TruncInst>(I))
+            Worklist.push_back(I);
+    }
+
+    for (auto I : Worklist) {
+        TruncInst *TI = cast<TruncInst>(I);
+        ZExtInst *ZI = dyn_cast<ZExtInst>(TI->getOperand(0));
+        if (!ZI)
+            continue;
+
+        Type *SrcTy = ZI->getOperand(0)->getType();
+        Type *DstTy = TI->getType();
+        if (SrcTy == DstTy) {
+            I->replaceAllUsesWith(ZI->getOperand(0));
+            if (TI->use_empty())
+                toErase.push_back(TI);
+            Changed = true;
+        }
+    }
+
+    if (toErase.size())
+        ProcessErase(toErase);
+
+    return Changed;
+}
+
+/*
+ * vim: ts=8 sts=4 sw=4 expandtab
+ */
+