From fbbb6884e108419692a88e28eeeaa92cfbc08122 Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Sun, 5 Jul 2020 00:48:05 +0300
Subject: [PATCH] [llvm-reduce] extractArgumentsFromModule(): 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 arguments 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.
---
 ...-multiple-use-of-args-in-same-instruction.py | 13 +++++++++++++
 ...-multiple-use-of-args-in-same-instruction.ll | 17 +++++++++++++++++
 .../llvm-reduce/deltas/ReduceArguments.cpp      |  9 ++++++---
 3 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/Reduce/Inputs/remove-multiple-use-of-args-in-same-instruction.py
 create mode 100644 llvm/test/Reduce/remove-multiple-use-of-args-in-same-instruction.ll

diff --git a/llvm/test/Reduce/Inputs/remove-multiple-use-of-args-in-same-instruction.py b/llvm/test/Reduce/Inputs/remove-multiple-use-of-args-in-same-instruction.py
new file mode 100644
index 00000000000000..93fa5c0bc29e7d
--- /dev/null
+++ b/llvm/test/Reduce/Inputs/remove-multiple-use-of-args-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-args-in-same-instruction.ll b/llvm/test/Reduce/remove-multiple-use-of-args-in-same-instruction.ll
new file mode 100644
index 00000000000000..4d280bcf2f314b
--- /dev/null
+++ b/llvm/test/Reduce/remove-multiple-use-of-args-in-same-instruction.ll
@@ -0,0 +1,17 @@
+; 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-args-in-same-instruction.py %s -o %t
+; RUN: cat %t | FileCheck -implicit-check-not=uninteresting %s
+
+declare void @use(i32, i32, i32)
+
+; CHECK-LABEL: @interesting(i32 %uninteresting1, i32 %uninteresting2, i32 %uninteresting3
+define void @interesting(i32 %uninteresting1, i32 %uninteresting2, i32 %uninteresting3) {
+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/ReduceArguments.cpp b/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
index d5f60aad36bc87..b7d92049a67a27 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
@@ -60,7 +60,7 @@ static void extractArgumentsFromModule(std::vector<Chunk> ChunksToKeep,
 
   for (auto *F : Funcs) {
     ValueToValueMapTy VMap;
-    std::vector<Instruction *> InstToDelete;
+    std::vector<WeakVH> InstToDelete;
     for (auto &A : F->args())
       if (!ArgsToKeep.count(&A)) {
         // By adding undesired arguments to the VMap, CloneFunction will remove
@@ -70,8 +70,11 @@ static void extractArgumentsFromModule(std::vector<Chunk> ChunksToKeep,
           if (auto *I = dyn_cast<Instruction>(*&U))
             InstToDelete.push_back(I);
       }
-    // Delete any instruction that uses the argument
-    for (auto *I : InstToDelete) {
+    // Delete any (unique) instruction that uses the argument
+    for (Value *V : InstToDelete) {
+      if (!V)
+        continue;
+      auto *I = cast<Instruction>(V);
       I->replaceAllUsesWith(UndefValue::get(I->getType()));
       I->eraseFromParent();
     }