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author | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-08-02 21:53:03 +0000 |
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committer | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-08-02 21:53:03 +0000 |
commit | 0e0a8806d49038b60a0c20427d9f410b01cbb012 (patch) | |
tree | 9a33b338d2ead7da2d2043b367fe301fe05b275a /lib/CodeGen/SpillPlacement.cpp | |
parent | f78faf84a85262bf76295dfc5d85e1e7a942a4f2 (diff) | |
download | llvm-0e0a8806d49038b60a0c20427d9f410b01cbb012.tar.gz llvm-0e0a8806d49038b60a0c20427d9f410b01cbb012.tar.bz2 llvm-0e0a8806d49038b60a0c20427d9f410b01cbb012.tar.xz |
Extend the SpillPlacement interface with two new features.
The PrefBoth constraint is used for blocks that ideally want a live-in
value both on the stack and in a register. This would be used by a block
that has a use before interference forces a spill.
Secondly, add the ChangesValue flag to BlockConstraint. This tells
SpillPlacement if a live-in value on the stack can be reused as a
live-out stack value for free. If the block redefines the virtual
register, a spill would be required for that.
This extra information will be used by SpillPlacement to more accurately
calculate spill costs when a value can exist both on the stack and in a
register.
The simplest example is a basic block that reads the virtual register,
but doesn't change its value. Spilling around such a block requires a
reload, but no spill in the block.
The spiller already knows this, but the spill placer doesn't. That can
sometimes lead to suboptimal regions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136731 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SpillPlacement.cpp')
-rw-r--r-- | lib/CodeGen/SpillPlacement.cpp | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/lib/CodeGen/SpillPlacement.cpp b/lib/CodeGen/SpillPlacement.cpp index ce7b37bfce..10a3c18962 100644 --- a/lib/CodeGen/SpillPlacement.cpp +++ b/lib/CodeGen/SpillPlacement.cpp @@ -220,6 +220,7 @@ void SpillPlacement::addConstraints(ArrayRef<BlockConstraint> LiveBlocks) { 0, // DontCare, 1, // PrefReg, -1, // PrefSpill + 0, // PrefBoth -HUGE_VALF // MustSpill }; |