[MemoryBuiltins] Handle phi nodes without operands (PR63013)

Conservatively return unknown in this degenerate case. This is
hard to hit in practice, because such phis are usually optimized
away before they reach a getObjectSize() call.

Fixes https://github.com/llvm/llvm-project/issues/63013.

diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index 9fabca2..6ff7aed 100644 (file)
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -984,6 +984,8 @@ SizeOffsetType ObjectSizeOffsetVisitor::combineSizeOffset(SizeOffsetType LHS,
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PN) {
+  if (PN.getNumIncomingValues() == 0)
+    return unknown();
   auto IncomingValues = PN.incoming_values();
   return std::accumulate(IncomingValues.begin() + 1, IncomingValues.end(),
                          compute(*IncomingValues.begin()),

diff --git a/llvm/test/Transforms/JumpThreading/pr63013.ll b/llvm/test/Transforms/JumpThreading/pr63013.ll
new file mode 100644 (file)
index 0000000..f7f60b4
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/pr63013.ll
@@ -0,0 +1,90 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -S -passes=jump-threading < %s | FileCheck %s
+
+; Make sure we don't crash while trying to calculate the object size of an
+; empty phi node.
+
+define void @test(i16 %arg) {
+; CHECK-LABEL: define void @test
+; CHECK-SAME: (i16 [[ARG:%.*]]) {
+; CHECK-NEXT:  start:
+; CHECK-NEXT:    br label [[BB8THREAD_PRE_SPLIT1:%.*]]
+; CHECK:       bb8thread-pre-split1:
+; CHECK-NEXT:    [[LOAD_PR_PR:%.*]] = load i16, ptr null, align 2
+; CHECK-NEXT:    br label [[BB8:%.*]]
+; CHECK:       bb8:
+; CHECK-NEXT:    [[LOAD_PR:%.*]] = phi i16 [ [[LOAD_PR_PR]], [[BB8THREAD_PRE_SPLIT1]] ], [ [[LOAD_PR]], [[BB8]] ]
+; CHECK-NEXT:    [[I:%.*]] = icmp eq i16 [[LOAD_PR]], 0
+; CHECK-NEXT:    br i1 [[I]], label [[BB10:%.*]], label [[BB8]]
+; CHECK:       bb10:
+; CHECK-NEXT:    [[I1:%.*]] = getelementptr { i128, i8 }, ptr null, i64 0, i32 1
+; CHECK-NEXT:    store i8 0, ptr [[I1]], align 8
+; CHECK-NEXT:    [[I2:%.*]] = load i128, ptr null, align 8
+; CHECK-NEXT:    [[I3:%.*]] = icmp eq i128 [[I2]], 0
+; CHECK-NEXT:    br i1 [[I3]], label [[BB8THREAD_PRE_SPLIT1]], label [[BB8THREAD_PRE_SPLIT1]]
+;
+start:
+  br label %bb5
+
+bb20:                                             ; preds = %bb19, %bb17, %bb17, %bb14, %bb13
+  ret void
+
+bb5:                                              ; preds = %bb16, %bb10, %bb10, %bb8, %start
+  %_11.0 = phi ptr [ %_11.5, %bb16 ], [ null, %bb10 ], [ null, %bb8 ], [ null, %bb10 ], [ null, %start ]
+  br label %bb8
+
+bb8:                                              ; preds = %bb15, %bb9, %bb5
+  %load = load i16, ptr null, align 2
+  %i = icmp eq i16 %load, 0
+  br i1 %i, label %bb9, label %bb5
+
+bb9:                                              ; preds = %bb8
+  switch i16 %load, label %bb8 [
+  i16 1, label %bb10
+  i16 0, label %bb13
+  ]
+
+bb10:                                             ; preds = %bb14, %bb13, %bb9
+  %_2.7 = phi ptr [ %_11.0, %bb14 ], [ %_11.0, %bb13 ], [ null, %bb9 ]
+  %i1 = getelementptr { i128, i8 }, ptr %_11.0, i64 0, i32 1
+  store i8 0, ptr %i1, align 8
+  %i2 = load i128, ptr %_2.7, align 8
+  %i3 = icmp eq i128 %i2, 0
+  br i1 %i3, label %bb5, label %bb5
+
+bb13:                                             ; preds = %bb14, %bb9
+  switch i128 0, label %bb20 [
+  i128 0, label %bb10
+  i128 1, label %bb14
+  ]
+
+bb14:                                             ; preds = %bb19, %bb13
+  switch i16 %arg, label %bb20 [
+  i16 0, label %bb13
+  i16 2, label %bb10
+  i16 1, label %bb15
+  ]
+
+bb15:                                             ; preds = %bb14
+  switch i16 %arg, label %bb16 [
+  i16 1, label %bb8
+  i16 0, label %bb17
+  ]
+
+bb16:                                             ; preds = %bb19, %bb15
+  %_11.5 = phi ptr [ null, %bb15 ], [ null, %bb19 ]
+  br label %bb5
+
+bb17:                                             ; preds = %bb19, %bb15
+  switch i16 %arg, label %bb20 [
+  i16 0, label %bb20
+  i16 1, label %bb19
+  ]
+
+bb19:                                             ; preds = %bb17
+  switch i16 %arg, label %bb16 [
+  i16 0, label %bb14
+  i16 1, label %bb20
+  i16 6570, label %bb17
+  ]
+}