Subzero: Improve handling of alloca instructions of constant size.

src/IceTargetLoweringARM32.cpp

 //===- subzero/src/IceTargetLoweringARM32.cpp - ARM32 lowering ------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 558 matching lines @@
 // Helper function for addProlog().
 //
 // This assumes Arg is an argument passed on the stack. This sets the frame
 // offset for Arg and updates InArgsSizeBytes according to Arg's width. For an
 // I64 arg that has been split into Lo and Hi components, it calls itself
 // recursively on the components, taking care to handle Lo first because of the
 // little-endian architecture. Lastly, this function generates an instruction
 // 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();
   InArgsSizeBytes = applyStackAlignmentTy(InArgsSizeBytes, Ty);
   Arg->setStackOffset(BasicFrameOffset + InArgsSizeBytes);
   InArgsSizeBytes += typeWidthInBytesOnStack(Ty);
   // If the argument variable has been assigned a register, we need to load the
   // value from the stack slot.
   if (Arg->hasReg()) {
     assert(Ty != IceType_i64);
@@ skipping 175 matching lines @@
       int32_t DummyReg;
       InRegs = CC.FPInReg(Ty, &DummyReg);
     } else if (Ty == IceType_i64) {
       std::pair<int32_t, int32_t> DummyRegs;
       InRegs = CC.I64InRegs(&DummyRegs);
     } else {
       assert(Ty == IceType_i32);
       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.
   assignVarStackSlots(SortedSpilledVariables, SpillAreaPaddingBytes,
                       SpillAreaSizeBytes, GlobalsAndSubsequentPaddingSize,
                       UsesFramePointer);
   this->HasComputedFrame = true;
 
   if (BuildDefs::dump() && Func->isVerbose(IceV_Frame)) {
     OstreamLocker L(Func->getContext());
@@ skipping 2562 matching lines @@
       << ".eabi_attribute 68, 1   @ Tag_Virtualization_use\n";
   if (CPUFeatures.hasFeature(TargetARM32Features::HWDivArm)) {
     Str << ".eabi_attribute 44, 2   @ Tag_DIV_use\n";
   }
   // Technically R9 is used for TLS with Sandboxing, and we reserve it.
   // However, for compatibility with current NaCl LLVM, don't claim that.
   Str << ".eabi_attribute 14, 3   @ Tag_ABI_PCS_R9_use: Not used\n";
 }
 
 } // end of namespace Ice