[RegisterCoalescer] Refine the terminal rule to still consider the terminal

nodes.
When a node is terminal it is pushed at the end of the list of the copies to
coalesce instead of being completely ignored. In effect, this reduces its
priority over non-terminal nodes.

Because of that, we do not miss the rematerialization opportunities, nor the
copies that can be merged with more complex, than the terminal rule,
interference checks.

Related to PR22768.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233395 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 9e3cf415e44f6aaa3b852d6d0246775da1db9673..c04437e21df05d5dbdebf104adc22ab638e2aa73 100644 (file)
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -2733,13 +2733,17 @@ bool RegisterCoalescer::applyTerminalRule(const MachineInstr &Copy) const {
     return false;
   // Check if the destination of this copy has any other affinity.
   unsigned DstReg = Copy.getOperand(0).getReg();
     return false;
   // Check if the destination of this copy has any other affinity.
   unsigned DstReg = Copy.getOperand(0).getReg();

+  unsigned SrcReg = Copy.getOperand(1).getReg();

   if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
   if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||

+      // If SrcReg is a physical register, the copy won't be coalesced.
+      // Ignoring it may have other side effect (like missing
+      // rematerialization). So keep it.
+      TargetRegisterInfo::isPhysicalRegister(SrcReg) ||

       !isTerminalReg(DstReg, Copy, MRI))
     return false;
 
   // DstReg is a terminal node. Check if it inteferes with any other
   // copy involving SrcReg.
       !isTerminalReg(DstReg, Copy, MRI))
     return false;
 
   // DstReg is a terminal node. Check if it inteferes with any other
   // copy involving SrcReg.

-  unsigned SrcReg = Copy.getOperand(1).getReg();

   const MachineBasicBlock *OrigBB = Copy.getParent();
   const LiveInterval &DstLI = LIS->getInterval(DstReg);
   for (const MachineInstr &MI : MRI->reg_nodbg_instructions(SrcReg)) {
   const MachineBasicBlock *OrigBB = Copy.getParent();
   const LiveInterval &DstLI = LIS->getInterval(DstReg);
   for (const MachineInstr &MI : MRI->reg_nodbg_instructions(SrcReg)) {


@@ -2775,25 +2779,45 @@ RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB) {
   // yet, it might invalidate the iterator.
   const unsigned PrevSize = WorkList.size();
   if (JoinGlobalCopies) {
   // yet, it might invalidate the iterator.
   const unsigned PrevSize = WorkList.size();
   if (JoinGlobalCopies) {

+    SmallVector<MachineInstr*, 2> LocalTerminals;
+    SmallVector<MachineInstr*, 2> GlobalTerminals;

     // Coalesce copies bottom-up to coalesce local defs before local uses. They
     // are not inherently easier to resolve, but slightly preferable until we
     // have local live range splitting. In particular this is required by
     // cmp+jmp macro fusion.
     for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
          MII != E; ++MII) {
     // Coalesce copies bottom-up to coalesce local defs before local uses. They
     // are not inherently easier to resolve, but slightly preferable until we
     // have local live range splitting. In particular this is required by
     // cmp+jmp macro fusion.
     for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
          MII != E; ++MII) {

-      if (!MII->isCopyLike() || applyTerminalRule(*MII))
+      if (!MII->isCopyLike())

         continue;
         continue;

-      if (isLocalCopy(&(*MII), LIS))
-        LocalWorkList.push_back(&(*MII));
-      else
-        WorkList.push_back(&(*MII));
+      bool ApplyTerminalRule = applyTerminalRule(*MII);
+      if (isLocalCopy(&(*MII), LIS)) {
+        if (ApplyTerminalRule)
+          LocalTerminals.push_back(&(*MII));
+        else
+          LocalWorkList.push_back(&(*MII));
+      } else {
+        if (ApplyTerminalRule)
+          GlobalTerminals.push_back(&(*MII));
+        else
+          WorkList.push_back(&(*MII));
+      }

     }
     }

+    // Append the copies evicted by the terminal rule at the end of the list.
+    LocalWorkList.append(LocalTerminals.begin(), LocalTerminals.end());
+    WorkList.append(GlobalTerminals.begin(), GlobalTerminals.end());

   }
   else {
   }
   else {

+    SmallVector<MachineInstr*, 2> Terminals;

      for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
           MII != E; ++MII)
      for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
           MII != E; ++MII)

-       if (MII->isCopyLike() && !applyTerminalRule(*MII))
-         WorkList.push_back(MII);
+       if (MII->isCopyLike()) {
+        if (applyTerminalRule(*MII))
+          Terminals.push_back(&(*MII));
+        else
+          WorkList.push_back(MII);
+       }
+     // Append the copies evicted by the terminal rule at the end of the list.
+     WorkList.append(Terminals.begin(), Terminals.end());

   }
   // Try coalescing the collected copies immediately, and remove the nulls.
   // This prevents the WorkList from getting too large since most copies are
   }
   // Try coalescing the collected copies immediately, and remove the nulls.
   // This prevents the WorkList from getting too large since most copies are

diff --git a/test/CodeGen/X86/sret-implicit.ll b/test/CodeGen/X86/sret-implicit.ll
index 3fade1de0cf09c8f19c22b74e6544000a0d1feb4..568095254078818b4c16fd16f4551400ec5e048a 100644 (file)
--- a/test/CodeGen/X86/sret-implicit.ll
+++ b/test/CodeGen/X86/sret-implicit.ll
@@ -1,5 +1,7 @@
 ; RUN: llc -mtriple=x86_64-apple-darwin8 < %s | FileCheck %s
 ; RUN: llc -mtriple=x86_64-pc-linux < %s | FileCheck %s
 ; RUN: llc -mtriple=x86_64-apple-darwin8 < %s | FileCheck %s
 ; RUN: llc -mtriple=x86_64-pc-linux < %s | FileCheck %s

+; RUN: llc -mtriple=x86_64-apple-darwin8 -terminal-rule < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-pc-linux -terminal-rule < %s | FileCheck %s

 
 ; CHECK-LABEL: return32
 ; CHECK-DAG: movq      $0, (%rdi)
 
 ; CHECK-LABEL: return32
 ; CHECK-DAG: movq      $0, (%rdi)