[PATCH] D21885: RegScavenging: Add scavengeRegisterBackwards()

[Daniel Sanders via llvm-commits]

dsanders added inline comments.

================
Comment at: test/CodeGen/Mips/emergency-spill-slot-near-fp.ll:3-5
@@ -2,2 +2,5 @@
 ; RUN: llc -march=mipsel -O0 -relocation-model=pic < %s | FileCheck %s
+; Disabled. Looks like the new register scavenging code can generate code
+; without an emergency spillslot here.
+; XFAIL: *
 
----------------
t.p.northover wrote:
> Don't we need to come up with an alternative that does need a spill slot then? Not that I actually have any idea how to do that on MIPS, but XFAILing the test probably means it'll just be forgotten forever.
I'd prefer not to xfail unless we have to.

> Not that I actually have any idea how to do that on MIPS

I think this test is relying on a stack frame that exceeds 16-bits and is using the '%unused_variable = alloca [16384 x i32], align 4' to make sure that happens. I'd guess that the change has made the stack frame smaller somehow and all the offsets fit in a 16-bit integer. Have some of the alloca's been optimized out?

The other causes of an emergency spill slot involve DSP accumulators and double-precision floats but they aren't used in this test.


Repository:
  rL LLVM

http://reviews.llvm.org/D21885