[WebAssembly] Fix p2align in assembler.

Summary:
- Match the syntax output by InstPrinter.
- Fix it always emitting 0 for align. Had to work around fact that
  opcode is not available for GetDefaultP2Align while parsing.
- Updated tests that were erroneously happy with a p2align=0

Fixes https://bugs.llvm.org/show_bug.cgi?id=40752

Reviewers: aheejin, sbc100

Subscribers: jgravelle-google, sunfish, jfb, llvm-commits, dschuff

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63633

llvm-svn: 364570

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 8790428b6c8..67532013afd 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -123,7 +123,7 @@ namespace llvm {
 namespace WebAssembly {
 
 /// Return the default p2align value for a load or store with the given opcode.
-inline unsigned GetDefaultP2Align(unsigned Opcode) {
+inline unsigned GetDefaultP2AlignAny(unsigned Opcode) {
   switch (Opcode) {
   case WebAssembly::LOAD8_S_I32:
   case WebAssembly::LOAD8_S_I32_S:
@@ -333,8 +333,16 @@ inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::STORE_v2f64_S:
     return 4;
   default:
+    return -1;
+  }
+}
+
+inline unsigned GetDefaultP2Align(unsigned Opcode) {
+  auto Align = GetDefaultP2AlignAny(Opcode);
+  if (Align == -1U) {
     llvm_unreachable("Only loads and stores have p2align values");
   }
+  return Align;
 }
 
 /// This is used to indicate block signatures.