[llvm] ce05211 - [Reduce] Argument reduction: don't try to drop terminator instructions

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2020-07-21T00:06:03+03:00
New Revision: ce052110ac9c03f14e16a0f46697da2eabc7ac4c

URL: https://github.com/llvm/llvm-project/commit/ce052110ac9c03f14e16a0f46697da2eabc7ac4c
DIFF: https://github.com/llvm/llvm-project/commit/ce052110ac9c03f14e16a0f46697da2eabc7ac4c.diff

LOG: [Reduce] Argument reduction: don't try to drop terminator instructions

Newly-added test previously crashed.

While it is up for debate whether or not instruction reduction
should be indiscriminate in instruction dropping (there you can
just ensure that the test case is still -verify'ies), here
if we drop terminator, CloneFunctionInto() will immediately crash.

So let's not do that :)

Added: 
    llvm/test/Reduce/remove-args-used-by-ret.ll

Modified: 
    llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/Reduce/remove-args-used-by-ret.ll b/llvm/test/Reduce/remove-args-used-by-ret.ll
new file mode 100644
index 000000000000..13b7fe58e5f0
--- /dev/null
+++ b/llvm/test/Reduce/remove-args-used-by-ret.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-reduce --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 %s
+
+; We can't drop arguments if they are used by terminator instructions.
+
+define i32 @t(i32 %a0, i32 %a1, i32 %a2) {
+; CHECK-ALL-LABEL: @t
+; CHECK-FINAL-NOT: %a1
+;
+; CHECK-INTERESTINGNESS: ret i32
+; CHECK-FINAL: ret i32 undef
+
+  ret i32 %a1
+}

diff  --git a/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp b/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
index 88c3e326ff97..e0e1d1c22567 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp
@@ -73,7 +73,8 @@ static void extractArgumentsFromModule(std::vector<Chunk> ChunksToKeep,
         continue;
       auto *I = cast<Instruction>(V);
       I->replaceAllUsesWith(UndefValue::get(I->getType()));
-      I->eraseFromParent();
+      if (!I->isTerminator())
+        I->eraseFromParent();
     }
 
     // No arguments to reduce