From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 19 Sep 2008 17:38:47 +0000 (+0000)
Subject: Re-materalized definition instructions may be dead. Whack them.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=20580a1cf658388f357d58a71ac81e4167acc34f;p=oota-llvm.git

Re-materalized definition instructions may be dead. Whack them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56352 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 0044f06d33d..2f4c8d38892 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -479,6 +479,7 @@ bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
   li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
   CopyMI->eraseFromParent();
   ReMatCopies.insert(CopyMI);
+  ReMatDefs.insert(DefMI);
   ++NumReMats;
   return true;
 }
@@ -2183,6 +2184,7 @@ void SimpleRegisterCoalescing::printRegName(unsigned reg) const {
 void SimpleRegisterCoalescing::releaseMemory() {
   JoinedCopies.clear();
   ReMatCopies.clear();
+  ReMatDefs.clear();
 }
 
 static bool isZeroLengthInterval(LiveInterval *li) {
@@ -2291,25 +2293,45 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
         continue;
       }
 
+      // Now check if this is a remat'ed def instruction which is now dead.
+      if (ReMatDefs.count(MI)) {
+        bool isDead = true;
+        for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+          const MachineOperand &MO = MI->getOperand(i);
+          if (!MO.isRegister() || MO.isDead())
+            continue;
+          unsigned Reg = MO.getReg();
+          if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
+              !mri_->use_empty(Reg)) {
+            isDead = false;
+            break;
+          }
+        }
+        if (isDead) {
+          li_->RemoveMachineInstrFromMaps(mii);
+          mii = mbbi->erase(mii);
+        }
+      }
+
       // If the move will be an identity move delete it
-      bool isMove = tii_->isMoveInstr(*mii, SrcReg, DstReg);
+      bool isMove = tii_->isMoveInstr(*MI, SrcReg, DstReg);
       if (isMove && SrcReg == DstReg) {
         if (li_->hasInterval(SrcReg)) {
           LiveInterval &RegInt = li_->getInterval(SrcReg);
           // If def of this move instruction is dead, remove its live range
           // from the dstination register's live interval.
-          if (mii->registerDefIsDead(DstReg)) {
-            if (!ShortenDeadCopySrcLiveRange(RegInt, mii))
-              ShortenDeadCopyLiveRange(RegInt, mii);
+          if (MI->registerDefIsDead(DstReg)) {
+            if (!ShortenDeadCopySrcLiveRange(RegInt, MI))
+              ShortenDeadCopyLiveRange(RegInt, MI);
           }
         }
-        li_->RemoveMachineInstrFromMaps(mii);
+        li_->RemoveMachineInstrFromMaps(MI);
         mii = mbbi->erase(mii);
         ++numPeep;
       } else if (!isMove || !TurnCopyIntoImpDef(mii, mbb, DstReg, SrcReg)) {
         SmallSet<unsigned, 4> UniqueUses;
-        for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
-          const MachineOperand &mop = mii->getOperand(i);
+        for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+          const MachineOperand &mop = MI->getOperand(i);
           if (mop.isRegister() && mop.getReg() &&
               TargetRegisterInfo::isVirtualRegister(mop.getReg())) {
             unsigned reg = mop.getReg();
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.h b/lib/CodeGen/SimpleRegisterCoalescing.h
index 39c90716b60..330c476dbf5 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -100,6 +100,10 @@ namespace llvm {
     ///
     SmallPtrSet<MachineInstr*, 32> ReMatCopies;
 
+    /// ReMatDefs - Keep track of definition instructions which have
+    /// been remat'ed.
+    SmallPtrSet<MachineInstr*, 8> ReMatDefs;
+
   public:
     static char ID; // Pass identifcation, replacement for typeid
     SimpleRegisterCoalescing() : MachineFunctionPass(&ID) {}
diff --git a/test/CodeGen/X86/coalescer-remat.ll b/test/CodeGen/X86/coalescer-remat.ll
new file mode 100644
index 00000000000..ab029f45658
--- /dev/null
+++ b/test/CodeGen/X86/coalescer-remat.ll
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin | grep xor | count 3
+
+@val = internal global i64 0		; <i64*> [#uses=1]
+@"\01LC" = internal constant [7 x i8] c"0x%lx\0A\00"		; <[7 x i8]*> [#uses=1]
+
+define i32 @main() nounwind {
+entry:
+	%0 = tail call i64 @llvm.atomic.cmp.swap.i64.p0i64(i64* @val, i64 0, i64 1)		; <i64> [#uses=1]
+	%1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr ([7 x i8]* @"\01LC", i32 0, i64 0), i64 %0) nounwind		; <i32> [#uses=0]
+	ret i32 0
+}
+
+declare i64 @llvm.atomic.cmp.swap.i64.p0i64(i64*, i64, i64) nounwind
+
+declare i32 @printf(i8*, ...) nounwind