[WebAssembly] Make returns variadic

Summary:
This is necessary and sufficient to get simple cases of multiple
return working with multivalue enabled. More complex cases will
require block and loop signatures to be generalized to potentially be
type indices as well.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68684

llvm-svn: 374235

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.cpp
index 94b2bac7e64..e4cc2389147 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.cpp
@@ -49,10 +49,12 @@ void llvm::computeSignatureVTs(const FunctionType *Ty, const Function &F,
   computeLegalValueVTs(F, TM, Ty->getReturnType(), Results);
 
   MVT PtrVT = MVT::getIntegerVT(TM.createDataLayout().getPointerSizeInBits());
-  if (Results.size() > 1) {
-    // WebAssembly currently can't lower returns of multiple values without
-    // demoting to sret (see WebAssemblyTargetLowering::CanLowerReturn). So
-    // replace multiple return values with a pointer parameter.
+  if (Results.size() > 1 &&
+      !TM.getSubtarget<WebAssemblySubtarget>(F).hasMultivalue()) {
+    // WebAssembly can't lower returns of multiple values without demoting to
+    // sret unless multivalue is enabled (see
+    // WebAssemblyTargetLowering::CanLowerReturn). So replace multiple return
+    // values with a poitner parameter.
     Results.clear();
     Params.push_back(PtrVT);
   }