Subzero: Improve handling of alloca instructions of constant size.

src/IceTargetLoweringARM32.cpp

Index: src/IceTargetLoweringARM32.cpp
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index d61d93cf0430b57ff316dd2ab95ce07b48f33acf..01d36495b3b26610b05580804b8d37c34d56d489 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -576,12 +576,15 @@ void TargetARM32::lowerArguments() {
 // to copy Arg into its assigned register if applicable.
 void TargetARM32::finishArgumentLowering(Variable *Arg, Variable *FramePtr,
                                          size_t BasicFrameOffset,
+                                         size_t StackAdjBytes,
                                          size_t &InArgsSizeBytes) {
   if (auto *Arg64On32 = llvm::dyn_cast<Variable64On32>(Arg)) {
     Variable *Lo = Arg64On32->getLo();
     Variable *Hi = Arg64On32->getHi();
-    finishArgumentLowering(Lo, FramePtr, BasicFrameOffset, InArgsSizeBytes);
-    finishArgumentLowering(Hi, FramePtr, BasicFrameOffset, InArgsSizeBytes);
+    finishArgumentLowering(Lo, FramePtr, BasicFrameOffset, StackAdjBytes,
+                           InArgsSizeBytes);
+    finishArgumentLowering(Hi, FramePtr, BasicFrameOffset, StackAdjBytes,
+                           InArgsSizeBytes);
     return;
   }
   Type Ty = Arg->getType();
@@ -777,8 +780,11 @@ void TargetARM32::addProlog(CfgNode *Node) {
       int32_t DummyReg;
       InRegs = CC.I32InReg(&DummyReg);
     }
-    if (!InRegs)
-      finishArgumentLowering(Arg, FramePtr, BasicFrameOffset, InArgsSizeBytes);
+    if (!InRegs) {
+      constexpr size_t StackAdjBytes = 0;
+      finishArgumentLowering(Arg, FramePtr, BasicFrameOffset, StackAdjBytes,
+                             InArgsSizeBytes);
+    }
   }
 
   // Fill in stack offsets for locals.