From 2463f67c4975adc4225abe276a373a33a036add7 Mon Sep 17 00:00:00 2001 From: Chad Rosier Date: Thu, 15 Nov 2012 18:13:20 +0000 Subject: [PATCH] [reg scavenger] Fix the isUsed/isAliasUsed functions so as to not report a false positive. In this particular case, R6 was being spilled by the register scavenger when it was in fact dead. The isUsed function reported R6 as used because the R6_R7 alias was reserved (due to the fact that we've reserved R7 as the FP). The solution is to only check if the original register (i.e., R6) isReserved and not the aliases. The aliases are only checked to make sure they're available. The test case is derived from one of the nightly tester benchmarks and is rather intractable and difficult to reproduce, so I haven't included it. rdar://12592448 llvm-svn: 168054 --- llvm/include/llvm/CodeGen/RegisterScavenging.h | 8 +++++--- llvm/lib/CodeGen/RegisterScavenging.cpp | 2 +- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/llvm/include/llvm/CodeGen/RegisterScavenging.h b/llvm/include/llvm/CodeGen/RegisterScavenging.h index 08d3169..8752e67 100644 --- a/llvm/include/llvm/CodeGen/RegisterScavenging.h +++ b/llvm/include/llvm/CodeGen/RegisterScavenging.h @@ -129,10 +129,12 @@ private: /// isReserved - Returns true if a register is reserved. It is never "unused". bool isReserved(unsigned Reg) const { return MRI->isReserved(Reg); } - /// isUsed / isUnused - Test if a register is currently being used. + /// isUsed - Test if a register is currently being used. When called by the + /// isAliasUsed function, we only check isReserved if this is the original + /// register, not an alias register. /// - bool isUsed(unsigned Reg) const { - return !RegsAvailable.test(Reg) || isReserved(Reg); + bool isUsed(unsigned Reg, bool CheckReserved = true) const { + return !RegsAvailable.test(Reg) || (CheckReserved && isReserved(Reg)); } /// isAliasUsed - Is Reg or an alias currently in use? diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp index 5ec6564..22d3c62 100644 --- a/llvm/lib/CodeGen/RegisterScavenging.cpp +++ b/llvm/lib/CodeGen/RegisterScavenging.cpp @@ -43,7 +43,7 @@ void RegScavenger::setUsed(unsigned Reg) { bool RegScavenger::isAliasUsed(unsigned Reg) const { for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) - if (isUsed(*AI)) + if (isUsed(*AI, *AI == Reg)) return true; return false; } -- 2.7.4