From 3a99693c5a9866f9e0ae3b7253e1952176e11df1 Mon Sep 17 00:00:00 2001
From: Andrew Trick <atrick@apple.com>
Date: Tue, 15 Oct 2013 03:39:43 +0000
Subject: Improve on r192635, ExeDepsFix for avx, and add a test case.

rdar:15221834 False AVX register dependencies cause 5x slowdown on
flops-5/6 and significant slowdown on several others.

This was blocking the switch to MI-Sched.

llvm-svn: 192669
---
 llvm/lib/CodeGen/ExecutionDepsFix.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'llvm/lib/CodeGen/ExecutionDepsFix.cpp')

diff --git a/llvm/lib/CodeGen/ExecutionDepsFix.cpp b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
index 0d26f9d4cba..031f19c135a 100644
--- a/llvm/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
@@ -557,6 +557,9 @@ void ExeDepsFix::processUndefReads(MachineBasicBlock *MBB) {
 
   for (MachineBasicBlock::reverse_iterator I = MBB->rbegin(), E = MBB->rend();
        I != E; ++I) {
+    // Update liveness, including the current instrucion's defs.
+    LiveUnits.stepBackward(*I, *TRI);
+
     if (UndefMI == &*I) {
       if (!LiveUnits.contains(UndefMI->getOperand(OpIdx).getReg(), *TRI))
         TII->breakPartialRegDependency(UndefMI, OpIdx, TRI);
@@ -568,7 +571,6 @@ void ExeDepsFix::processUndefReads(MachineBasicBlock *MBB) {
       UndefMI = UndefReads.back().first;
       OpIdx = UndefReads.back().second;
     }
-    LiveUnits.stepBackward(*I, *TRI);
   }
 }
 
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