From f804bd586ee58199db4cfb2da8e9ef067425900b Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Sun, 5 Jul 2020 01:01:46 +0300
Subject: [PATCH] [llvm-reduce] extractGVsFromModule(): don't crash when
 deleting instr twice

As it can be seen in newly-added (previously-crashing) test-case,
there can be a situation where multiple GV's are used in instr,
and we would schedule the same instruction to be deleted several times,
crashing when trying to delete it the second time.

We could either store WeakVH (done here), or use something set-like.
I think using WeakVH is prevalent in these cases elsewhere.
---
 ...tiple-use-of-global-vars-in-same-instruction.py | 13 ++++++++++++
 ...tiple-use-of-global-vars-in-same-instruction.ll | 24 ++++++++++++++++++++++
 llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp |  9 +++++---
 3 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/Reduce/Inputs/remove-multiple-use-of-global-vars-in-same-instruction.py
 create mode 100644 llvm/test/Reduce/remove-multiple-use-of-global-vars-in-same-instruction.ll

diff --git a/llvm/test/Reduce/Inputs/remove-multiple-use-of-global-vars-in-same-instruction.py b/llvm/test/Reduce/Inputs/remove-multiple-use-of-global-vars-in-same-instruction.py
new file mode 100644
index 0000000..93fa5c0
--- /dev/null
+++ b/llvm/test/Reduce/Inputs/remove-multiple-use-of-global-vars-in-same-instruction.py
@@ -0,0 +1,13 @@
+import sys
+
+FunctionCallPresent = False
+
+input = open(sys.argv[1], "r")
+for line in input:
+  if "call void @use" in line:
+    FunctionCallPresent = True
+
+if FunctionCallPresent:
+  sys.exit(0) # Interesting!
+
+sys.exit(1)
diff --git a/llvm/test/Reduce/remove-multiple-use-of-global-vars-in-same-instruction.ll b/llvm/test/Reduce/remove-multiple-use-of-global-vars-in-same-instruction.ll
new file mode 100644
index 0000000..c8b6390
--- /dev/null
+++ b/llvm/test/Reduce/remove-multiple-use-of-global-vars-in-same-instruction.ll
@@ -0,0 +1,24 @@
+; Test that llvm-reduce can remove uninteresting function arguments from function definitions as well as their calls.
+;
+; RUN: rm -rf %t
+; RUN: llvm-reduce --test %python --test-arg %p/Inputs/remove-multiple-use-of-global-vars-in-same-instruction.py %s -o %t
+; RUN: cat %t | FileCheck -implicit-check-not=uninteresting %s
+
+; CHECK: @uninteresting1 = global
+; CHECK: @uninteresting2 = global
+; CHECK: @uninteresting3 = global
+@uninteresting1 = global i32 0, align 4
+@uninteresting2 = global i32 0, align 4
+@uninteresting3 = global i32 0, align 4
+
+declare void @use(i32*, i32*, i32*)
+
+; CHECK-LABEL: @interesting()
+define void @interesting() {
+entry:
+  ; CHECK: call void @use(i32* @uninteresting1, i32* @uninteresting2, i32* @uninteresting3)
+  call void @use(i32* @uninteresting1, i32* @uninteresting2, i32* @uninteresting3)
+  call void @use(i32* @uninteresting1, i32* @uninteresting2, i32* @uninteresting3)
+  call void @use(i32* @uninteresting1, i32* @uninteresting2, i32* @uninteresting3)
+  ret void
+}
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp b/llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
index 843ca46..55d732c 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
@@ -33,7 +33,7 @@ static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
 
   // Delete out-of-chunk GVs and their uses
   std::vector<GlobalVariable *> ToRemove;
-  std::vector<Instruction *> InstToRemove;
+  std::vector<WeakVH> InstToRemove;
   for (auto &GV : Program->globals())
     if (GV.hasInitializer() && !GVsToKeep.count(&GV)) {
       for (auto U : GV.users())
@@ -44,8 +44,11 @@ static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
       ToRemove.push_back(&GV);
     }
 
-  // Delete Instruction uses of unwanted GVs
-  for (auto *Inst : InstToRemove) {
+  // Delete (unique) Instruction uses of unwanted GVs
+  for (Value *V : InstToRemove) {
+    if (!V)
+      continue;
+    auto *Inst = cast<Instruction>(V);
     Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
     Inst->eraseFromParent();
   }
-- 
2.7.4