[Hexagon] Clear the flow queue after visiting a single instruction

llvm-svn: 281339

2 files changed, 52 insertions, 0 deletions

diff --git a/llvm/lib/Target/Hexagon/BitTracker.cpp b/llvm/lib/Target/Hexagon/BitTracker.cpp
index 29b2d9f9429..c0591c332de 100644
--- a/llvm/lib/Target/Hexagon/BitTracker.cpp
+++ b/llvm/lib/Target/Hexagon/BitTracker.cpp
@@ -1054,6 +1054,11 @@ void BT::visit(const MachineInstr &MI) {
   assert(!MI.isBranch() && "Only non-branches are allowed");
   InstrExec.insert(&MI);
   visitNonBranch(MI);
+  // The call to visitNonBranch could propagate the changes until a branch
+  // is actually visited. This could result in adding CFG edges to the flow
+  // queue. Since the queue won't be processed, clear it.
+  while (!FlowQ.empty())
+    FlowQ.pop();
 }
 
 
diff --git a/llvm/test/CodeGen/Hexagon/bit-visit-flowq.ll b/llvm/test/CodeGen/Hexagon/bit-visit-flowq.ll
new file mode 100644
index 00000000000..b44847dee68
--- /dev/null
+++ b/llvm/test/CodeGen/Hexagon/bit-visit-flowq.ll
@@ -0,0 +1,47 @@
+; RUN: llc -march=hexagon < %s | FileCheck %s
+; REQUIRES: asserts
+
+; Check that we don't crash.
+; CHECK: call bar
+
+target triple = "hexagon"
+
+@debug = external hidden unnamed_addr global i1, align 4
+
+; Function Attrs: nounwind
+define void @foo() local_unnamed_addr #0 {
+entry:
+  br label %if.end5
+
+if.end5:                                          ; preds = %entry
+  br i1 undef, label %if.then12, label %if.end13
+
+if.then12:                                        ; preds = %if.end5
+  unreachable
+
+if.end13:                                         ; preds = %if.end5
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.end13
+  %or.cond288 = or i1 undef, undef
+  br i1 undef, label %if.then44, label %if.end51
+
+if.then44:                                        ; preds = %for.cond
+  tail call void @bar() #0
+  br label %if.end51
+
+if.end51:                                         ; preds = %if.then44, %for.cond
+  %.b433 = load i1, i1* @debug, align 4
+  %or.cond290 = and i1 %or.cond288, %.b433
+  br i1 %or.cond290, label %if.then55, label %if.end63
+
+if.then55:                                        ; preds = %if.end51
+  unreachable
+
+if.end63:                                         ; preds = %if.end51
+  unreachable
+}
+
+declare void @bar() local_unnamed_addr #0
+
+attributes #0 = { nounwind }