[PATCH] D114590: [CodeGen] Emit alignment "Max Skip" operand for align directives

[Nicholas Guy via Phabricator via llvm-commits]

NickGuy updated this revision to Diff 391026.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D114590/new/

https://reviews.llvm.org/D114590

Files:
  llvm/include/llvm/CodeGen/AsmPrinter.h
  llvm/include/llvm/CodeGen/MachineBasicBlock.h
  llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp


Index: llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2447,7 +2447,7 @@
 // two boundary.  If a global value is specified, and if that global has
 // an explicit alignment requested, it will override the alignment request
 // if required for correctness.
-void AsmPrinter::emitAlignment(Align Alignment, const GlobalObject *GV) const {
+void AsmPrinter::emitAlignment(Align Alignment, const GlobalObject *GV, unsigned MaxBytesToEmit) const {
   if (GV)
     Alignment = getGVAlignment(GV, GV->getParent()->getDataLayout(), Alignment);
 
@@ -2460,7 +2460,7 @@
       STI = &getSubtargetInfo();
     else
       STI = TM.getMCSubtargetInfo();
-    OutStreamer->emitCodeAlignment(Alignment.value(), STI);
+    OutStreamer->emitCodeAlignment(Alignment.value(), STI, MaxBytesToEmit);
   } else
     OutStreamer->emitValueToAlignment(Alignment.value());
 }
@@ -3253,7 +3253,7 @@
   // Emit an alignment directive for this block, if needed.
   const Align Alignment = MBB.getAlignment();
   if (Alignment != Align(1))
-    emitAlignment(Alignment);
+    emitAlignment(Alignment, nullptr, MBB.getMaxBytesForAlignment());
 
   // Switch to a new section if this basic block must begin a section. The
   // entry block is always placed in the function section and is handled
Index: llvm/include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -136,6 +136,11 @@
   /// Alignment of the basic block. One if the basic block does not need to be
   /// aligned.
   Align Alignment;
+  /// Maximum amount of bytes that can be added to align the basic block.
+  /// Zero to represent no maximum.
+  /// Values greater than Alignment^2 are understood to be functionally useless,
+  /// and are equivalent to a value of Zero.
+  uint8_t MaxBytesForAlignment = 0;
 
   /// Indicate that this basic block is entered via an exception handler.
   bool IsEHPad = false;
@@ -521,6 +526,11 @@
   /// Set alignment of the basic block.
   void setAlignment(Align A) { Alignment = A; }
 
+  /// Return the maximum amount of padding allowed for aligning the basic block
+  uint8_t getMaxBytesForAlignment() const { return MaxBytesForAlignment; }
+  /// Set the maximum amount of padding allowed for aligning the basic block
+  void setMaxBytesForAlignment(uint8_t MaxBytes) { MaxBytesForAlignment = MaxBytes; }
+
   /// Returns true if the block is a landing pad. That is this basic block is
   /// entered via an exception handler.
   bool isEHPad() const { return IsEHPad; }
Index: llvm/include/llvm/CodeGen/AsmPrinter.h
===================================================================
--- llvm/include/llvm/CodeGen/AsmPrinter.h
+++ llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -432,7 +432,7 @@
   /// global value is specified, and if that global has an explicit alignment
   /// requested, it will override the alignment request if required for
   /// correctness.
-  void emitAlignment(Align Alignment, const GlobalObject *GV = nullptr) const;
+  void emitAlignment(Align Alignment, const GlobalObject *GV = nullptr, unsigned MaxBytesToEmit = 0) const;
 
   /// Lower the specified LLVM Constant to an MCExpr.
   virtual const MCExpr *lowerConstant(const Constant *CV);


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