[PATCH] D21395: Fix for Bug 28144

[Vivek Pandya via llvm-commits]

vivekvpandya created this revision.
vivekvpandya added reviewers: mehdi_amini, qcolombet, hfinkel, MatzeB.
vivekvpandya added subscribers: llvm-commits, mcrosier, karthikthecool.

This patch contains fix for the bug https://llvm.org/bugs/show_bug.cgi?id=28144 related to register usage calculation, previously it was not considering callee RegMasks at callsites in the Machinefunction thus generating wrong register usage information.
This patch also makes AsmPrinter print call preserved registers as comment at call sites in generated assembly.

http://reviews.llvm.org/D21395

Files:
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  lib/CodeGen/RegUsageInfoCollector.cpp

Index: lib/CodeGen/RegUsageInfoCollector.cpp
===================================================================
--- lib/CodeGen/RegUsageInfoCollector.cpp
+++ lib/CodeGen/RegUsageInfoCollector.cpp
@@ -86,8 +86,7 @@
 
 bool RegUsageInfoCollector::runOnMachineFunction(MachineFunction &MF) {
   MachineRegisterInfo *MRI = &MF.getRegInfo();
-  TargetRegisterInfo *TRI =
-      (TargetRegisterInfo *)MF.getSubtarget().getRegisterInfo();
+  const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
   const TargetMachine &TM = MF.getTarget();
 
   DEBUG(dbgs() << " -------------------- " << getPassName()
@@ -107,17 +106,31 @@
   PRUI->setTargetMachine(&TM);
 
   DEBUG(dbgs() << "Clobbered Registers: ");
-  for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg) {
+  for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg)
     if (!MRI->reg_nodbg_empty(PReg) && MRI->isPhysRegUsed(PReg))
       markRegClobbered(TRI, &RegMask[0], PReg);
-  }
 
   const uint32_t *CallPreservedMask =
       TRI->getCallPreservedMask(MF, MF.getFunction()->getCallingConv());
   // Set callee saved register as preserved.
-  for (unsigned index = 0; index < regMaskSize; index++) {
+  for (unsigned index = 0; index < regMaskSize; index++)
     RegMask[index] = RegMask[index] | CallPreservedMask[index];
+
+  for (MachineBasicBlock &MBB : MF) {
+    for (MachineInstr &MI : MBB) {
+      if (!MI.isCall())
+        continue;
+      for (MachineOperand &MO : MI.operands()) {
+        if (MO.isRegMask()) {
+          const uint32_t *CalleeRegMask = MO.getRegMask();
+          for (unsigned index = 0; index < regMaskSize; index++)
+            RegMask[index] = RegMask[index] & CalleeRegMask[index];
+          break;
+        }
+      }
+    }
   }
+
   for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg) {
     if (MachineOperand::clobbersPhysReg(&(RegMask[0]), PReg))
       DEBUG(dbgs() << TRI->getName(PReg) << " ");
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"
@@ -625,6 +626,7 @@
 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;
@@ -655,6 +657,23 @@
   // 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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