[WebAssembly] Convert the remaining unit tests to the new wasm-object-file target.

To facilitate this, add a new hidden command-line option to disable
the explicit-locals pass. That causes llc to emit invalid code that doesn't
have all locals converted to get_local/set_local, however it simplifies
testwriting in many cases.

llvm-svn: 296540

2 files changed, 28 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/README.txt b/llvm/lib/Target/WebAssembly/README.txt
index 3be7007a57f..3433b1553e8 100644
--- a/llvm/lib/Target/WebAssembly/README.txt
+++ b/llvm/lib/Target/WebAssembly/README.txt
@@ -150,3 +150,19 @@ Add support for mergeable sections in the Wasm writer, such as for strings and
 floating-point constants.
 
 //===---------------------------------------------------------------------===//
+
+The function @dynamic_alloca_redzone in test/CodeGen/WebAssembly/userstack.ll
+ends up with a tee_local in its prolog which has an unused result, requiring
+an extra drop:
+
+    get_global  $push8=, 0
+    tee_local   $push9=, 1, $pop8
+    drop        $pop9
+    [...]
+
+The prologue code initially thinks it needs an FP register, but later it
+turns out to be unneeded, so one could either approach this by being more
+clever about not inserting code for an FP in the first place, or optimizing
+away the copy later.
+
+//===---------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 50ee79b7079..41249117ae0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -31,6 +31,14 @@ using namespace llvm;
 
 #define DEBUG_TYPE "wasm-explicit-locals"
 
+// A command-line option to disable this pass. Note that this produces output
+// which is not valid WebAssembly, though it may be more convenient for writing
+// LLVM unit tests with.
+static cl::opt<bool> DisableWebAssemblyExplicitLocals(
+    "disable-wasm-explicit-locals", cl::ReallyHidden,
+    cl::desc("WebAssembly: Disable emission of get_local/set_local."),
+    cl::init(false));
+
 namespace {
 class WebAssemblyExplicitLocals final : public MachineFunctionPass {
   StringRef getPassName() const override {
@@ -164,6 +172,10 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
                   "********** Function: "
                << MF.getName() << '\n');
 
+  // Disable this pass if directed to do so.
+  if (DisableWebAssemblyExplicitLocals)
+    return false;
+
   // Disable this pass if we aren't doing direct wasm object emission.
   if (MF.getSubtarget<WebAssemblySubtarget>()
         .getTargetTriple().isOSBinFormatELF())