[llvm] df308ca - fix some bad logic that was removing all successor phi nodes, not just

[John Regehr via llvm-commits]

Author: John Regehr
Date: 2022-08-13T19:15:26-06:00
New Revision: df308cab28bdf53bb159d2927fc25ffab5a79fe7

URL: https://github.com/llvm/llvm-project/commit/df308cab28bdf53bb159d2927fc25ffab5a79fe7
DIFF: https://github.com/llvm/llvm-project/commit/df308cab28bdf53bb159d2927fc25ffab5a79fe7.diff

LOG: fix some bad logic that was removing all successor phi nodes, not just
out of chunk ones. the non-default second argument to
removePredecessor() is necessary to avoid creating invalid IR on
examples like the one in the provided test case

Differential Revision: https://reviews.llvm.org/D131843

Added: 
    llvm/test/tools/llvm-reduce/remove-bbs-nocrash.ll

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

Removed: 
    


################################################################################
diff  --git a/llvm/test/tools/llvm-reduce/remove-bbs-nocrash.ll b/llvm/test/tools/llvm-reduce/remove-bbs-nocrash.ll
new file mode 100644
index 0000000000000..d4a64be3acc7b
--- /dev/null
+++ b/llvm/test/tools/llvm-reduce/remove-bbs-nocrash.ll
@@ -0,0 +1,29 @@
+; RUN: llvm-reduce -abort-on-invalid-reduction --delta-passes=basic-blocks --test FileCheck --test-arg --check-prefix=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+
+; CHECK-INTERESTINGNESS: ret
+
+
+
+define void @f(ptr nocapture %arg, ptr %arg1) {
+bb:
+  br i1 false, label %bb2, label %bb26
+
+bb2:                                              ; preds = %bb
+  br label %bb4
+
+bb4:                                              ; preds = %bb2
+  br label %bb5
+
+bb5:                                              ; preds = %bb5, %bb4
+  %i = phi i64 [ 0, %bb4 ], [ %i9, %bb5 ]
+  %i6 = getelementptr inbounds i64, ptr %arg, i64 %i
+  %i7 = load i64, ptr %i6, align 8
+  %i8 = getelementptr inbounds i64, ptr %arg1, i64 %i
+  store i64 0, ptr %i8, align 8
+  %i9 = add nuw nsw i64 %i, 1
+  %i10 = icmp eq i64 %i9, 0
+  br i1 %i10, label %bb26, label %bb5
+
+bb26:                                             ; preds = %bb5, %bb
+  ret void
+}

diff  --git a/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp b/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
index fdd5770cd988c..1cef2a162d797 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
@@ -147,11 +147,9 @@ static void extractBasicBlocksFromModule(Oracle &O, Module &Program) {
   }
 
   // Remove out-of-chunk BB from successor phi nodes
-  for (auto &F : Program) {
-    for (auto &BB : F) {
-      for (auto *Succ : successors(&BB))
-        Succ->removePredecessor(&BB);
-    }
+  for (auto &BB : BBsToDelete) {
+    for (auto *Succ : successors(BB))
+      Succ->removePredecessor(BB, /*KeepOneInputPHIs=*/true);
   }
 
   // Replace terminators that reference out-of-chunk BBs