[PATCH] D113787: [llvm-reduce] keep terminator instructions during ReduceGlobalVars

[Dwight Guth via Phabricator via llvm-commits]

dwightguth created this revision.
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Previously we were deleting instructions that use a global variable when
we delete the global variable. However, this obviously does not work if
the instruction is a terminator instruction as the resulting basic block
will have no terminator, resulting in invalid IR. To fix this, we simply
ensure that terminator instructions are never added to the list of
instructions to delete.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113787

Files:
  llvm/test/tools/llvm-reduce/remove-global-vars-terminator.ll
  llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp


Index: llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
===================================================================
--- llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
+++ llvm/tools/llvm-reduce/deltas/ReduceGlobalVars.cpp
@@ -38,7 +38,8 @@
     if (!GVsToKeep.count(&GV)) {
       for (auto *U : GV.users())
         if (auto *Inst = dyn_cast<Instruction>(U))
-          InstToRemove.push_back(Inst);
+          if (!Inst->isTerminator())
+            InstToRemove.push_back(Inst);
 
       GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
       ToRemove.push_back(&GV);
Index: llvm/test/tools/llvm-reduce/remove-global-vars-terminator.ll
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-reduce/remove-global-vars-terminator.ll
@@ -0,0 +1,21 @@
+; Test that llvm-reduce does not create invalid IR when the global-variables
+; delta pass processes a global variable that is used by a basic block
+; terminator
+
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=global-variables --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL --implicit-check-not=uninteresting %s
+
+; CHECK-INTERESTINGNESS: @interesting = {{.*}}global i32{{.*}}, align 4
+
+; CHECK-FINAL: @interesting = global i32 0, align 4
+ at interesting = global i32 0, align 4
+
+ at uninteresting = global i32 1, align 4
+
+define i32* @foo() {
+entry:
+  ; CHECK-ALL: store i32 5, i32* @interesting, align 4
+  store i32 5, i32* @interesting, align 4
+
+  ret i32* @uninteresting
+}


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