Split the argument unscheduling loop in the WebAssembly register

coloring pass. Turn the logic into "look for an insert point and
then move things past the insert point".

No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253626 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp b/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp
index 7f27e7cede6ad12e9ece20e3bbcc91fa6e64e8ce..bf21024a731b0fd3103ad903d871938561b7fa5f 100644 (file)
--- a/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp
@@ -98,20 +98,30 @@ bool WebAssemblyRegColoring::runOnMachineFunction(MachineFunction &MF) {
 
   // FIXME: If scheduling has moved an ARGUMENT virtual register, move it back,
   // and recompute liveness. This is a temporary hack.
-  bool SawNonArg = false;
   bool MovedArg = false;
   MachineBasicBlock &EntryMBB = MF.front();
-  for (auto MII = EntryMBB.begin(); MII != EntryMBB.end(); ) {
-    MachineInstr *MI = &*MII++;
+  MachineBasicBlock::iterator InsertPt = EntryMBB.end();
+  // Look for the first NonArg instruction.
+  for (auto MII = EntryMBB.begin(), MIE = EntryMBB.end(); MII != MIE; ++MII) {
+    MachineInstr *MI = MII;
+    if (MI->getOpcode() != WebAssembly::ARGUMENT_I32 &&
+        MI->getOpcode() != WebAssembly::ARGUMENT_I64 &&
+        MI->getOpcode() != WebAssembly::ARGUMENT_F32 &&
+        MI->getOpcode() != WebAssembly::ARGUMENT_F64) {
+      InsertPt = MII;
+      break;
+    }
+  }
+  // Now move any argument instructions later in the block
+  // to before our first NonArg instruction.
+  for (auto I = InsertPt, E = EntryMBB.end(); I != E; ++I) {
+    MachineInstr *MI = I;
     if (MI->getOpcode() == WebAssembly::ARGUMENT_I32 ||
         MI->getOpcode() == WebAssembly::ARGUMENT_I64 ||
         MI->getOpcode() == WebAssembly::ARGUMENT_F32 ||
         MI->getOpcode() == WebAssembly::ARGUMENT_F64) {
-      EntryMBB.insert(EntryMBB.begin(), MI->removeFromParent());
-      if (SawNonArg)
-        MovedArg = true;
-    } else {
-      SawNonArg = true;
+      EntryMBB.insert(InsertPt, MI->removeFromParent());
+      MovedArg = true;
     }
   }
   if (MovedArg) {