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Geoff Berry 7825276490 [MachineCopyPropagation] Extend pass to do COPY source forwarding
This change extends MachineCopyPropagation to do COPY source forwarding.

This change also extends the MachineCopyPropagation pass to be able to
be run during register allocation, after physical registers have been
assigned, but before the virtual registers have been re-written, which
allows it to remove virtual register COPY LiveIntervals that become dead
through the forwarding of all of their uses.

Reviewers: qcolombet, javed.absar, MatzeB, jonpa

Subscribers: jyknight, nemanjai, llvm-commits, nhaehnle, mcrosier, mgorny

Differential Revision: https://reviews.llvm.org/D30751

llvm-svn: 311038
2017-08-16 20:50:01 +00:00

47 lines
1.1 KiB
LLVM

; RUN: llc -mtriple=aarch64-linux-gnu -verify-machineinstrs -o - %s | FileCheck %s
; LSR used to pick a sub-optimal solution due to the target responding
; conservatively to isLegalAddImmediate for negative values.
declare void @foo(i32)
define void @test(i32 %px) {
; CHECK_LABEL: test:
; CHECK_LABEL: %entry
; CHECK: subs [[REG0:w[0-9]+]],
; CHECK: csel {{w[0-9]+}}, wzr, [[REG0]]
entry:
%sub = add nsw i32 %px, -1
%cmp = icmp slt i32 %px, 1
%.sub = select i1 %cmp, i32 0, i32 %sub
br label %for.body
for.body:
; CHECK_LABEL: %for.body
; CHECK: cmp
; CHECK-NEXT: b.eq
; CHECK-LABEL: %if.then3
%x.015 = phi i32 [ %inc, %for.inc ], [ %.sub, %entry ]
%cmp2 = icmp eq i32 %x.015, %px
br i1 %cmp2, label %for.inc, label %if.then3
if.then3:
tail call void @foo(i32 %x.015)
br label %for.inc
for.inc:
; CHECK_LABEL: %for.inc
; CHECK: cmp
; CHECK-NEXT: add
; CHECK-NEXT: b.le
; CHECK_LABEL: %for.cond.cleanup
%inc = add nsw i32 %x.015, 1
%cmp1 = icmp sgt i32 %x.015, %px
br i1 %cmp1, label %for.cond.cleanup.loopexit, label %for.body
for.cond.cleanup.loopexit:
br label %for.cond.cleanup
for.cond.cleanup:
ret void
}