Changes in directory llvm/lib/CodeGen:
VirtRegMap.cpp updated: 1.47 -> 1.48
---
Log message:
Add code that checks for noop copies, which triggers when either:
1. a target doesn't know how to fold load/stores into copies, or
2. the spiller rewrites the input to a copy to the same register as the dest
instead of to the reloaded reg.
This will be moved/improved in the near future, but allows elimination of
some ancient x86 hacks. This eliminates 92 copies from SMG2000 on X86 and
163 copies from 252.eon.
---
Diffs of the changes: (+13 -0)
VirtRegMap.cpp | 13 +++++++++++++
1 files changed, 13 insertions(+)
Index: llvm/lib/CodeGen/VirtRegMap.cpp
diff -u llvm/lib/CodeGen/VirtRegMap.cpp:1.47
llvm/lib/CodeGen/VirtRegMap.cpp:1.48
--- llvm/lib/CodeGen/VirtRegMap.cpp:1.47 Thu Feb 2 18:36:31 2006
+++ llvm/lib/CodeGen/VirtRegMap.cpp Thu Feb 2 20:02:59 2006
@@ -38,6 +38,7 @@
Statistic<> NumLoads ("spiller", "Number of loads added");
Statistic<> NumReused("spiller", "Number of values reused");
Statistic<> NumDSE ("spiller", "Number of dead stores elided");
+ Statistic<> NumDCE ("spiller", "Number of copies elided");
enum SpillerName { simple, local };
@@ -658,6 +659,18 @@
}
}
}
+
+ // Okay, the instruction has been completely processed, input and output
+ // registers have been added. As a final sanity check, make sure this is
+ // not a noop-copy. If it is, nuke it.
+ {
+ unsigned Src, Dst;
+ if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
+ ++NumDCE;
+ DEBUG(std::cerr << "Removing now-noop copy: " << MI);
+ MBB.erase(&MI);
+ }
+ }
ProcessNextInst:
MII = NextMII;
}
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