scavenger gets confused about register liveness if it doesn't see them.
I'm not thrilled with this solution, but it only comes up when there are dead
copies in the code, which is something that hopefully doesn't happen much.
Here is what happens in pr4100: As shown in the following excerpt from the
debug output of llc, the source of a move gets reloaded from the stack,
inserting a new load instruction before the move. Since that source operand
is a kill, the physical register is free to be reused for the destination
of the move. The move ends up being a no-op, copying R3 to R3, so it is
deleted. But, it leaves behind the load to reload %reg1028 into R3, and
that load is not updated to show that it's destination operand (R3) is dead.
The scavenger gets confused by that load because it thinks that R3 is live.
Starting RegAlloc of: %reg1025<def,dead> = MOVr %reg1028<kill>, 14, %reg0, %reg0
Regs have values:
Reloading %reg1028 into R3
Last use of R3[%reg1028], removing it from live set
Assigning R3 to %reg1025
Register R3 [%reg1025] is never used, removing it from live set
Alternative solutions might be either marking the load as dead, or zapping
the load along with the no-op copy. I couldn't see an easy way to do
either of those, though.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71196 91177308-0d34-0410-b5e6-96231b3b80d8
checking for bcopy... no
checking for getc_unlocked... Assertion failed: (0 && "Unknown SCEV kind!"), function operator(), file /Volumes/Sandbox/Buildbot/llvm/full-llvm/build/llvmCore.roots/llvmCore~obj/src/lib/Analysis/ScalarEvolution.cpp, line 511.
/Volumes/Sandbox/Buildbot/llvm/full-llvm/build/llvmgcc42.roots/llvmgcc42~obj/src/libdecnumber/decUtility.c:360: internal compiler error: Abort trap
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://developer.apple.com/bugreporter> for instructions.
make[4]: *** [decUtility.o] Error 1
make[4]: *** Waiting for unfinished jobs....
Assertion failed: (0 && "Unknown SCEV kind!"), function operator(), file /Volumes/Sandbox/Buildbot/llvm/full-llvm/build/llvmCore.roots/llvmCore~obj/src/lib/Analysis/ScalarEvolution.cpp, line 511.
/Volumes/Sandbox/Buildbot/llvm/full-llvm/build/llvmgcc42.roots/llvmgcc42~obj/src/libdecnumber/decNumber.c:5591: internal compiler error: Abort trap
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://developer.apple.com/bugreporter> for instructions.
make[4]: *** [decNumber.o] Error 1
make[3]: *** [all-stage2-libdecnumber] Error 2
make[3]: *** Waiting for unfinished jobs....
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71165 91177308-0d34-0410-b5e6-96231b3b80d8
allow it to have multiple CFG edges to that block. This is needed
to allow MachineBasicBlock::isOnlyReachableByFallthrough to work
correctly. This fixes PR4126.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71018 91177308-0d34-0410-b5e6-96231b3b80d8
shows up in -print-machineinstrs. This doesn't appear to affect anything, but it was
weird for some DBG_LABELs to have DebugLocs but not all of them.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70921 91177308-0d34-0410-b5e6-96231b3b80d8
VirtRegMap keeps track of allocations so it knows what's not used. As a horrible hack, the stack coloring can color spill slots with *free* registers. That is, it replace reload and spills with copies from and to the free register. It unfold instructions that load and store the spill slot and replace them with register using variants.
Not yet enabled. This is part 1. More coming.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70787 91177308-0d34-0410-b5e6-96231b3b80d8
This is *not* turned on by default. Testing indicates this is just as likely to pessimize code. The main issue seems to be allocation preference doesn't work effectively. That will change once I've taught register allocator "swapping".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70503 91177308-0d34-0410-b5e6-96231b3b80d8
memory operands otherwise the writebacks get lost when the inline asm
doesn't otherwise have side effects. This fixes rdar://6839427, though
clang really shouldn't generate these anymore.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70455 91177308-0d34-0410-b5e6-96231b3b80d8
