ARM: do not add a regmask for TAILJUMPs

The jump doesn't really kill the registers, the following call does but
we never get back anyway.
This avoids some verify-machineinstrs problems when TAILJUMPs are
if-converted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191962 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 53 insertions, 16 deletions

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index a2c6f0c..c1ed4a6 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1779,24 +1779,26 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                                   RegsToPass[i].second.getValueType()));
 
   // Add a register mask operand representing the call-preserved registers.
-  const uint32_t *Mask;
-  const TargetRegisterInfo *TRI = getTargetMachine().getRegisterInfo();
-  const ARMBaseRegisterInfo *ARI = static_cast<const ARMBaseRegisterInfo*>(TRI);
-  if (isThisReturn) {
-    // For 'this' returns, use the R0-preserving mask if applicable
-    Mask = ARI->getThisReturnPreservedMask(CallConv);
-    if (!Mask) {
-      // Set isThisReturn to false if the calling convention is not one that
-      // allows 'returned' to be modeled in this way, so LowerCallResult does
-      // not try to pass 'this' straight through 
-      isThisReturn = false;
+  if (!isTailCall) {
+    const uint32_t *Mask;
+    const TargetRegisterInfo *TRI = getTargetMachine().getRegisterInfo();
+    const ARMBaseRegisterInfo *ARI = static_cast<const ARMBaseRegisterInfo*>(TRI);
+    if (isThisReturn) {
+      // For 'this' returns, use the R0-preserving mask if applicable
+      Mask = ARI->getThisReturnPreservedMask(CallConv);
+      if (!Mask) {
+        // Set isThisReturn to false if the calling convention is not one that
+        // allows 'returned' to be modeled in this way, so LowerCallResult does
+        // not try to pass 'this' straight through
+        isThisReturn = false;
+        Mask = ARI->getCallPreservedMask(CallConv);
+      }
+    } else
       Mask = ARI->getCallPreservedMask(CallConv);
-    }
-  } else
-    Mask = ARI->getCallPreservedMask(CallConv);
 
-  assert(Mask && "Missing call preserved mask for calling convention");
-  Ops.push_back(DAG.getRegisterMask(Mask));
+    assert(Mask && "Missing call preserved mask for calling convention");
+    Ops.push_back(DAG.getRegisterMask(Mask));
+  }
 
   if (InFlag.getNode())
     Ops.push_back(InFlag);
diff --git a/test/CodeGen/ARM/ifconv-regmask.ll b/test/CodeGen/ARM/ifconv-regmask.ll
new file mode 100644
index 0000000..d45f65f
--- /dev/null
+++ b/test/CodeGen/ARM/ifconv-regmask.ll
@@ -0,0 +1,35 @@
+; RUN: llc < %s -mtriple=thumbv7s-apple-ios6.0.0 -verify-machineinstrs
+
+%union.opcode = type { i32 }
+
+@opcode = external global %union.opcode, align 4
+
+; Function Attrs: nounwind ssp
+define i32 @sfu() {
+entry:
+  %bf.load = load i32* getelementptr inbounds (%union.opcode* @opcode, i32 0, i32 0), align 4
+  %bf.lshr = lshr i32 %bf.load, 26
+  %bf.clear = and i32 %bf.lshr, 7
+  switch i32 %bf.clear, label %return [
+    i32 0, label %sw.bb
+    i32 1, label %sw.bb1
+  ]
+
+sw.bb:                                            ; preds = %entry
+  %call = tail call i32 @func0()
+  br label %return
+
+sw.bb1:                                           ; preds = %entry
+  %call2 = tail call i32 @func1()
+  br label %return
+
+return:                                           ; preds = %sw.bb1, %sw.bb, %entry
+  %retval.0 = phi i32 [ %call2, %sw.bb1 ], [ %call, %sw.bb ], [ -1, %entry ]
+  ret i32 %retval.0
+}
+
+; Function Attrs: nounwind ssp
+declare i32 @func0()
+
+; Function Attrs: nounwind ssp
+declare i32 @func1()