[WebAssembly] Fix RegNumbering for the stack pointer

Previously it failed to add NumArgRegs to the offset and so clobbered an
already-used register. Now just start the numbering after the arg regs
and don't duplicate the add. Test coverage for this coming shortly with
the implementation of byval.

llvm-svn: 258597

1 files changed, 13 insertions, 5 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
index a583079..88c50a0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
@@ -74,6 +74,8 @@ bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
     case WebAssembly::ARGUMENT_I64:
     case WebAssembly::ARGUMENT_F32:
     case WebAssembly::ARGUMENT_F64:
+      DEBUG(dbgs() << "Arg VReg " << MI.getOperand(0).getReg() << " -> WAReg "
+                   << MI.getOperand(1).getImm() << "\n");
       MFI.setWAReg(MI.getOperand(0).getReg(), MI.getOperand(1).getImm());
       break;
     default:
@@ -84,26 +86,32 @@ bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
   // Then assign regular WebAssembly registers for all remaining used
   // virtual registers. TODO: Consider sorting the registers by frequency of
   // use, to maximize usage of small immediate fields.
-  unsigned NumArgRegs = MFI.getParams().size();
   unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
   unsigned NumStackRegs = 0;
-  unsigned CurReg = 0;
+  // Start the numbering for locals after the arg regs
+  unsigned CurReg = MFI.getParams().size();
   for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
     unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx);
     // Handle stackified registers.
     if (MFI.isVRegStackified(VReg)) {
+      DEBUG(dbgs() << "VReg " << VReg << " -> WAReg "
+                   << (INT32_MIN | NumStackRegs) << "\n");
       MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
       continue;
     }
     // Skip unused registers.
     if (MRI.use_empty(VReg))
       continue;
-    if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg)
-      MFI.setWAReg(VReg, NumArgRegs + CurReg++);
+    if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) {
+      DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n");
+      MFI.setWAReg(VReg, CurReg++);
+    }
   }
   // Allocate locals for used physical registers
-  if (FrameInfo.getStackSize() > 0)
+  if (FrameInfo.getStackSize() > 0) {
+    DEBUG(dbgs() << "PReg SP " << CurReg << "\n");
     MFI.addPReg(WebAssembly::SP32, CurReg++);
+  }
 
   return true;
 }