From e5e7946018844978d0ac09fdb35998a53b43ad34 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 19 Aug 2010 18:33:29 +0000
Subject: [PATCH] It's possible to sink a def if its local uses are PHI's.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111537 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineSink.cpp            | 10 +++----
 test/CodeGen/X86/MachineSink-PHIUse.ll | 39 ++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 5 deletions(-)
 create mode 100644 test/CodeGen/X86/MachineSink-PHIUse.ll

diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp
index d79b3751ece..2f8e9ffdf9d 100644
--- a/lib/CodeGen/MachineSink.cpp
+++ b/lib/CodeGen/MachineSink.cpp
@@ -103,15 +103,14 @@ bool MachineSinking::AllUsesDominatedByBlock(unsigned Reg,
     // Determine the block of the use.
     MachineInstr *UseInst = &*I;
     MachineBasicBlock *UseBlock = UseInst->getParent();
-    if (UseBlock == DefMBB) {
-      LocalUse = true;
-      return false;
-    }
 
     if (UseInst->isPHI()) {
       // PHI nodes use the operand in the predecessor block, not the block with
       // the PHI.
       UseBlock = UseInst->getOperand(I.getOperandNo()+1).getMBB();
+    } else if (UseBlock == DefMBB) {
+      LocalUse = true;
+      return false;
     }
 
     // Check that it dominates.
@@ -270,7 +269,6 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
   // decide.
   MachineBasicBlock *SuccToSinkTo = 0;
 
-  bool LocalUse = false;
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = MI->getOperand(i);
     if (!MO.isReg()) continue;  // Ignore non-register operands.
@@ -328,6 +326,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
       if (SuccToSinkTo) {
         // If a previous operand picked a block to sink to, then this operand
         // must be sinkable to the same block.
+        bool LocalUse = false;
         if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, ParentBlock, LocalUse))
           return false;
 
@@ -338,6 +337,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
       // we should sink to.
       for (MachineBasicBlock::succ_iterator SI = ParentBlock->succ_begin(),
            E = ParentBlock->succ_end(); SI != E; ++SI) {
+        bool LocalUse = false;
         if (AllUsesDominatedByBlock(Reg, *SI, ParentBlock, LocalUse)) {
           SuccToSinkTo = *SI;
           break;
diff --git a/test/CodeGen/X86/MachineSink-PHIUse.ll b/test/CodeGen/X86/MachineSink-PHIUse.ll
new file mode 100644
index 00000000000..728e3773601
--- /dev/null
+++ b/test/CodeGen/X86/MachineSink-PHIUse.ll
@@ -0,0 +1,39 @@
+; RUN: llc < %s -mtriple=x86_64-appel-darwin -stats |& grep {machine-sink}
+
+define fastcc void @t() nounwind ssp {
+entry:
+  br i1 undef, label %bb, label %bb4
+
+bb:                                               ; preds = %entry
+  br i1 undef, label %return, label %bb3
+
+bb3:                                              ; preds = %bb
+  unreachable
+
+bb4:                                              ; preds = %entry
+  br i1 undef, label %bb.nph, label %return
+
+bb.nph:                                           ; preds = %bb4
+  br label %bb5
+
+bb5:                                              ; preds = %bb9, %bb.nph
+  %indvar = phi i64 [ 0, %bb.nph ], [ %tmp12, %bb9 ] ; <i64> [#uses=1]
+  %tmp12 = add i64 %indvar, 1                     ; <i64> [#uses=2]
+  %tmp13 = trunc i64 %tmp12 to i32                ; <i32> [#uses=0]
+  br i1 undef, label %bb9, label %bb6
+
+bb6:                                              ; preds = %bb5
+  br i1 undef, label %bb9, label %bb7
+
+bb7:                                              ; preds = %bb6
+  br i1 undef, label %bb9, label %bb8
+
+bb8:                                              ; preds = %bb7
+  unreachable
+
+bb9:                                              ; preds = %bb7, %bb6, %bb5
+  br i1 undef, label %bb5, label %return
+
+return:                                           ; preds = %bb9, %bb4, %bb
+  ret void
+}