When lowering the 'resume' instruction, look to see if we can eliminate the

'insertvalue' instructions that recreate the structure returned by the
'landingpad' instruction. Because the 'insertvalue' instruction isn't supported
by FastISel, this can save a bit of time during -O0 compilation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148520 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp
index aa442233e5c4ef27688a59b69be21f528783e74d..f2b2977275197b0cca3b2364e0a7162d74186f02 100644 (file)
--- a/lib/CodeGen/DwarfEHPrepare.cpp
+++ b/lib/CodeGen/DwarfEHPrepare.cpp
@@ -101,10 +101,40 @@ bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
          I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
     ResumeInst *RI = *I;
     BranchInst::Create(UnwindBB, RI->getParent());
-    ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0),
-                                                        0, "exn.obj", RI);
+
+    Value *V = RI->getOperand(0);
+    Instruction *ExnObj = 0;
+    InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
+    LoadInst *SelLoad = 0;
+    InsertValueInst *ExcIVI = 0;
+    bool EraseIVIs = false;
+    if (SelIVI) {
+      if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
+        ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
+        if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
+            ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
+          ExnObj = cast<Instruction>(ExcIVI->getOperand(1));
+          SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
+          EraseIVIs = true;
+        }
+      }
+    }
+
+    if (!ExnObj)
+      ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
+
     PN->addIncoming(ExnObj, RI->getParent());
     RI->eraseFromParent();
+
+    if (EraseIVIs) {
+      if (SelIVI->getNumUses() == 0)
+        SelIVI->eraseFromParent();
+      if (ExcIVI->getNumUses() == 0)
+        ExcIVI->eraseFromParent();
+      if (SelLoad && SelLoad->getNumUses() == 0)
+        SelLoad->eraseFromParent();
+    }
+
     ++NumResumesLowered;
   }