[PATCH] D21490: Print call preserved registers in comments at call site in assembly files.

[Vivek Pandya via llvm-commits]

vivekvpandya added a reviewer: MatzeB.
vivekvpandya updated this revision to Diff 61373.
vivekvpandya added a comment.

Updated patch to fetch latest changes in AsmPrinter.cpp. I also feel that it would be good to add an option similar to  -asm-show-inst  in llc to control this printing. So what are reviewer's thoughts ?


http://reviews.llvm.org/D21490

Files:
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp

Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -27,6 +27,7 @@
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
+#include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/Mangler.h"
@@ -623,6 +624,7 @@
 static void emitComments(const MachineInstr &MI, raw_ostream &CommentOS) {
   const MachineFunction *MF = MI.getParent()->getParent();
   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
 
   // Check for spills and reloads
   int FI;
@@ -653,6 +655,22 @@
   // Check for spill-induced copies
   if (MI.getAsmPrinterFlag(MachineInstr::ReloadReuse))
     CommentOS << " Reload Reuse\n";
+
+  if (MI.isCall()) {
+    const uint32_t *CalleeRegMask;
+    CommentOS << "Call Preserved Registers: ";
+
+    for (const MachineOperand &MO : MI.operands())
+      if (MO.isRegMask()) {
+        CalleeRegMask = MO.getRegMask();
+        break;
+      }
+
+    for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg)
+      if (!MachineOperand::clobbersPhysReg(CalleeRegMask, PReg))
+        CommentOS << TRI->getName(PReg) << " ";
+    CommentOS << "\n";
+  }
 }
 
 /// emitImplicitDef - This method emits the specified machine instruction


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