SIL: let the function entry block be the parent block of SILUndefs in the function.

Author: eeckstein

lib/SIL/IR/SILValue.cpp

@@ -209,6 +209,10 @@ SILBasicBlock *SILNode::getParentBlock() const {
   if (auto *MVR = dyn_cast<MultipleValueInstructionResult>(this)) {
     return MVR->getParent()->getParent();
   }
+  if (auto *undef = dyn_cast<SILUndef>(this)) {
+    // By convention, undefs are considered to be defined at the entry of the function.
+    return undef->getParent()->getEntryBlock();
+  }
   return nullptr;
 }
 

test/SILOptimizer/simplify_cfg_args.sil

@@ -745,14 +745,14 @@ enum ThreeWay {
 
 // CHECK-LABEL: sil hidden [noinline] @testUnwrapEnumArg : $@convention(thin) () -> () {
 // CHECK: bb0:
-// CHECK:   br bb1(undef : $Builtin.Int64, %{{.*}} : $Payload)
-// CHECK: bb1(%{{.*}} : $Builtin.Int64, %{{.*}} : $Payload):
+// CHECK:   br bb1(%{{.*}} : $Payload)
+// CHECK: bb1(%{{.*}} : $Payload):
 // CHECK:   alloc_stack $Payload
 // CHECK:   switch_enum undef : $ThreeWay, case #ThreeWay.one!enumelt: bb4, case #ThreeWay.two!enumelt: bb2, case #ThreeWay.three!enumelt: bb3
 // CHECK: bb2:
 // CHECK:   [[P2:%.*]] = load %{{.*}} : $*Payload
 // CHECK:   dealloc_stack %{{.*}} : $*Payload
-// CHECK:   br bb1(undef : $Builtin.Int64, [[P2]] : $Payload)
+// CHECK:   br bb1([[P2]] : $Payload)
 // CHECK: bb3:
 // CHECK:   [[P3:%.*]] = load %{{.*}} : $*Payload
 // CHECK:   dealloc_stack %{{.*}} : $*Payload
@@ -764,7 +764,7 @@ enum ThreeWay {
 // CHECK: bb5:
 // CHECK:   br bb7
 // CHECK: bb6:
-// CHECK:   br bb1(undef : $Builtin.Int64, [[P4]] : $Payload)
+// CHECK:   br bb1([[P4]] : $Payload)
 // CHECK: bb7:
 // CHECK:   return %{{.*}} : $()
 // CHECK-LABEL: } // end sil function 'testUnwrapEnumArg'

test/SILOptimizer/simplify_cfg_args_ossa.sil

@@ -723,14 +723,14 @@ enum ThreeWay {
 
 // CHECK-LABEL: sil hidden [noinline] [ossa] @testUnwrapEnumArg : $@convention(thin) () -> () {
 // CHECK: bb0:
-// CHECK:   br bb1(undef : $Builtin.Int64, %{{.*}} : $Payload)
-// CHECK: bb1(%{{.*}} : $Builtin.Int64, %{{.*}} : $Payload):
+// CHECK:   br bb1(%{{.*}} : $Payload)
+// CHECK: bb1(%{{.*}} : $Payload):
 // CHECK:   alloc_stack $Payload
 // CHECK:   switch_enum undef : $ThreeWay, case #ThreeWay.one!enumelt: bb4, case #ThreeWay.two!enumelt: bb2, case #ThreeWay.three!enumelt: bb3
 // CHECK: bb2:
 // CHECK:   [[P2:%.*]] = load [trivial] %{{.*}} : $*Payload
 // CHECK:   dealloc_stack %{{.*}} : $*Payload
-// CHECK:   br bb1(undef : $Builtin.Int64, [[P2]] : $Payload)
+// CHECK:   br bb1([[P2]] : $Payload)
 // CHECK: bb3:
 // CHECK:   [[P3:%.*]] = load [trivial] %{{.*}} : $*Payload
 // CHECK:   dealloc_stack %{{.*}} : $*Payload
@@ -740,7 +740,7 @@ enum ThreeWay {
 // CHECK:   dealloc_stack %{{.*}} : $*Payload
 // CHECK:   cond_br undef, bb6, bb5
 // CHECK: bb5:
-// CHECK:   br bb1(undef : $Builtin.Int64, [[P4]] : $Payload)
+// CHECK:   br bb1([[P4]] : $Payload)
 // CHECK: bb6:
 // CHECK:   br bb7
 // CHECK: bb7: