From 1e3aeefc088db2fe32958eb17f46e60011d34949 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Fri, 3 Sep 2010 18:36:56 +0000
Subject: [PATCH] VirtRegRewriter checks for early clobbers before it reuses an
 available stack slot.

Teach it to also check for early clobbered aliases, and early clobber operands
following the current operand.

This fixes the miscompilation in PR8044 where EC registers eax and ecx were
being used for inputs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112988 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/VirtRegRewriter.cpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index 94a64ceec93..d988e106c52 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -2027,14 +2027,16 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
           CanReuse = !ReusedOperands.isClobbered(PhysReg) &&
             Spills.canClobberPhysReg(PhysReg);
         }
-        // If this is an asm, and PhysReg is used elsewhere as an earlyclobber
-        // operand, we can't also use it as an input.  (Outputs always come
-        // before inputs, so we can stop looking at i.)
+        // If this is an asm, and a PhysReg alias is used elsewhere as an
+        // earlyclobber operand, we can't also use it as an input.
         if (MI.isInlineAsm()) {
-          for (unsigned k=0; k<i; ++k) {
+          for (unsigned k = 0, e = MI.getNumOperands(); k != e; ++k) {
             MachineOperand &MOk = MI.getOperand(k);
-            if (MOk.isReg() && MOk.getReg()==PhysReg && MOk.isEarlyClobber()) {
+            if (MOk.isReg() && MOk.isEarlyClobber() &&
+                TRI->regsOverlap(MOk.getReg(), PhysReg)) {
               CanReuse = false;
+              DEBUG(dbgs() << "Not reusing physreg " << TRI->getName(PhysReg)
+                           << " for vreg" << VirtReg << ": " << MOk << '\n');
               break;
             }
           }
-- 
2.34.1