GlobalISel: support 'undef' constant.

llvm-svn: 278174

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index ef83630..a5f62cf 100644 (file)
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -318,12 +318,14 @@ bool IRTranslator::translate(const Instruction &Inst) {
 }
 
 bool IRTranslator::translate(const Constant &C, unsigned Reg) {
-  if (auto CI = dyn_cast<ConstantInt>(&C)) {
+  if (auto CI = dyn_cast<ConstantInt>(&C))
     EntryBuilder.buildConstant(LLT{*CI->getType()}, Reg, CI->getZExtValue());
-    return true;
-  }
+  else if (isa<UndefValue>(C))
+    EntryBuilder.buildInstr(TargetOpcode::IMPLICIT_DEF).addDef(Reg);
+  else
+    llvm_unreachable("unhandled constant kind");
 
-  llvm_unreachable("unhandled constant kind");
+  return true;
 }
 
 

diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
index 7546cfa..e63b851 100644 (file)
--- a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
@@ -363,3 +363,10 @@ define i32 @constant_int_start() {
   %res = add i32 2, 42
   ret i32 %res
 }
+
+; CHECK-LABEL: name: test_undef
+; CHECK: [[UNDEF:%[0-9]+]](32) = IMPLICIT_DEF
+; CHECK: %w0 = COPY [[UNDEF]]
+define i32 @test_undef() {
+  ret i32 undef
+}