MI Sched: eliminate local vreg copies.

For now, we just reschedule instructions that use the copied vregs and
let regalloc elliminate it. I would really like to eliminate the
copies on-the-fly during scheduling, but we need a complete
implementation of repairIntervalsInRange() first.

The general strategy is for the register coalescer to eliminate as
many global copies as possible and shrink live ranges to be
extended-basic-block local. The coalescer should not have to worry
about resolving local copies (e.g. it shouldn't attemp to reorder
instructions). The scheduler is a much better place to deal with local
interference. The coalescer side of this equation needs work.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180193 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 0 deletions

diff --git a/test/CodeGen/ARM/misched-copy-arm.ll b/test/CodeGen/ARM/misched-copy-arm.ll
new file mode 100644
index 0000000000..4b15326008
--- /dev/null
+++ b/test/CodeGen/ARM/misched-copy-arm.ll
@@ -0,0 +1,30 @@
+; REQUIRES: asserts
+; RUN: llc < %s -march=thumb -mcpu=swift -pre-RA-sched=source -enable-misched -verify-misched -debug-only=misched -o - 2>&1 > /dev/null | FileCheck %s
+;
+; Loop counter copies should be eliminated.
+; There is also a MUL here, but we don't care where it is scheduled.
+; CHECK: postinc
+; CHECK: *** Final schedule for BB#2 ***
+; CHECK: t2LDRs
+; CHECK: t2ADDrr
+; CHECK: t2CMPrr
+; CHECK: COPY
+define i32 @postinc(i32 %a, i32* nocapture %d, i32 %s) nounwind {
+entry:
+  %cmp4 = icmp eq i32 %a, 0
+  br i1 %cmp4, label %for.end, label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i32 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %s.05 = phi i32 [ %mul, %for.body ], [ 0, %entry ]
+  %indvars.iv.next = add i32 %indvars.iv, %s
+  %arrayidx = getelementptr inbounds i32* %d, i32 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %mul = mul nsw i32 %0, %s.05
+  %exitcond = icmp eq i32 %indvars.iv.next, %a
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  %s.0.lcssa = phi i32 [ 0, %entry ], [ %mul, %for.body ]
+  ret i32 %s.0.lcssa
+}