... Just make sure we check uses first so we see the kill first. It
turns out ignoring defs gives some pretty nasty runtime failures.
I'm certain this is the fix but I'm still reducing a testcase.
llvm-svn: 217735
Vector MUL/MLAs have tied operands, which gives us extra constraints
that we currently can't handle. Instead of silently doing the wrong
thing, remove support to be readded later properly.
llvm-svn: 217690
Defs are seen before uses, so a def without the kill flag doesn't necessarily
mean that the register is not killed on that instruction. It may be killed
in a later use operand.
llvm-svn: 217689
and forget about the previously used accumulator.
Coming up with a simple testcase is not easy, as this highly depends on
what the register allocator is doing: this issue showed up while working
with the PBQP allocator, which produced a different allocation scheme.
A testcase would need to come up with chain starting in D[0-7], then
moving to D[8-15], followed by a call to a function whose regmask
clobbers the starting accumulator in D[0-7], then another use of the chain.
Fixed some formatting, added some invariant checks while there.
llvm-svn: 216721
It seems on Darwin the illegal round-trip ::iterator -> MachineInstr* -> ::iterator breaks execution horribly when the iterator is not a real MachineInstr, like ::end().
llvm-svn: 216455
std::map invalidates the iterator to any element that gets deleted, which means
we can't increment it correctly afterwards. This was causing Darwin test
failures.
llvm-svn: 215233
For best-case performance on Cortex-A57, we should try to use a balanced mix of odd and even D-registers when performing a critical sequence of independent, non-quadword FP/ASIMD floating-point multiply or multiply-accumulate operations.
This pass attempts to detect situations where the register allocation may adversely affect this load balancing and to change the registers used so as to better utilize the CPU.
Ideally we'd just take each multiply or multiply-accumulate in turn and allocate it alternating even or odd registers. However, multiply-accumulates are most efficiently performed in the same functional unit as their accumulation operand. Therefore this pass tries to find maximal sequences ("Chains") of multiply-accumulates linked via their accumulation operand, and assign them all the same "color" (oddness/evenness).
This optimization affects S-register and D-register floating point multiplies and FMADD/FMAs, as well as vector (floating point only) muls and FMADD/FMA. Q register instructions (and 128-bit vector instructions) are not affected.
llvm-svn: 215199
