[llvm] a5bb247 - [llvm-reduce] Create returns with undef values for non-void functions.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2020-08-31T16:33:46+01:00
New Revision: a5bb24758d02e1e42b72561d0ddbd682776d1a4d

URL: https://github.com/llvm/llvm-project/commit/a5bb24758d02e1e42b72561d0ddbd682776d1a4d
DIFF: https://github.com/llvm/llvm-project/commit/a5bb24758d02e1e42b72561d0ddbd682776d1a4d.diff

LOG: [llvm-reduce] Create returns with undef values for non-void functions.

Currently replaceBranchTerminator/removeUninterestingBBsFromSwitch
always creates `ret void` instructions if no successor is in the chunk.

This results in invalid IR for functions with non-void return types,
which makes those reductions unfeasible. Instead, create `ret ty undef`
for functions with non-void return types.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D86849

Added: 
    

Modified: 
    llvm/test/Reduce/remove-bbs-ret-nonvoid.ll
    llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/Reduce/remove-bbs-ret-nonvoid.ll b/llvm/test/Reduce/remove-bbs-ret-nonvoid.ll
index 198da95ad901..8a87064315a9 100644
--- a/llvm/test/Reduce/remove-bbs-ret-nonvoid.ll
+++ b/llvm/test/Reduce/remove-bbs-ret-nonvoid.ll
@@ -13,10 +13,7 @@ define i32 @main(i1 %c) {
 ; CHECK-NEXT:    br label %interesting2
 
 ; CHECK-LABEL: interesting2:
-; CHECK-NEXT:    br label %uninteresting1
-
-; CHECK-LABEL: uninteresting1:
-; CHECK-NEXT:    ret i32 10
+; CHECK-NEXT:    ret i32 undef
 
 interesting:
   br label %interesting2

diff  --git a/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp b/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
index 9dee738d4906..8c0832dd884a 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
@@ -45,7 +45,10 @@ static void replaceBranchTerminator(BasicBlock &BB,
   Term->eraseFromParent();
 
   if (ChunkSucessors.empty()) {
-    ReturnInst::Create(BB.getContext(), nullptr, &BB);
+    auto *FnRetTy = BB.getParent()->getReturnType();
+    ReturnInst::Create(BB.getContext(),
+                       FnRetTy->isVoidTy() ? nullptr : UndefValue::get(FnRetTy),
+                       &BB);
     return;
   }
 
@@ -66,7 +69,10 @@ static void replaceBranchTerminator(BasicBlock &BB,
 static void removeUninterestingBBsFromSwitch(SwitchInst &SwInst,
                                              std::set<BasicBlock *> BBsToKeep) {
   if (!BBsToKeep.count(SwInst.getDefaultDest())) {
-    ReturnInst::Create(SwInst.getContext(), nullptr, SwInst.getParent());
+    auto *FnRetTy = SwInst.getParent()->getParent()->getReturnType();
+    ReturnInst::Create(SwInst.getContext(),
+                       FnRetTy->isVoidTy() ? nullptr : UndefValue::get(FnRetTy),
+                       SwInst.getParent());
     SwInst.eraseFromParent();
   } else
     for (int I = 0, E = SwInst.getNumCases(); I != E; ++I) {