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[RISCV][MCP] Remove redundant move from tail duplication (#89865)

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Tail duplication will generate the redundant move before return. It is
because the MachineCopyPropogation can't recognize COPY after post-RA
pseudoExpand.

This patch make MachineCopyPropogation recognize `%0 = ADDI %1, 0` as
COPY
This commit is contained in:
Piyou Chen
2024-08-28 08:32:54 +08:00
committed by GitHub
parent 32abe5d49b
commit 2def1c4458
2 changed files with 51 additions and 1 deletions
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2
llvm/lib/CodeGen/MachineCopyPropagation.cpp
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@@ -1053,7 +1053,7 @@ void MachineCopyPropagation::BackwardCopyPropagateBlock(
// Ignore non-trivial COPYs.
std::optional<DestSourcePair> CopyOperands =
isCopyInstr(MI, *TII, UseCopyInstr);
if (CopyOperands && MI.getNumOperands() == 2) {
if (CopyOperands) {
Register DefReg = CopyOperands->Destination->getReg();
Register SrcReg = CopyOperands->Source->getReg();

50
llvm/test/CodeGen/RISCV/redundant-copy-from-tail-duplicate.ll Normal file
View File

@@ -0,0 +1,50 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
; RUN: llc < %s -mtriple=riscv64 -mattr=+v | FileCheck %s
define signext i32 @sum(ptr %a, i32 signext %n, i1 %prof.min.iters.check, <vscale x 8 x i1> %0, <vscale x 8 x i1> %1) {
; CHECK-LABEL: sum:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: andi a2, a2, 1
; CHECK-NEXT: beqz a2, .LBB0_4
; CHECK-NEXT: # %bb.1: # %for.body.preheader
; CHECK-NEXT: li a3, 0
; CHECK-NEXT: .LBB0_2: # %for.body
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: mv a2, a3
; CHECK-NEXT: lw a3, 0(a0)
; CHECK-NEXT: addi a0, a0, 4
; CHECK-NEXT: bnez a1, .LBB0_2
; CHECK-NEXT: # %bb.3: # %for.end
; CHECK-NEXT: mv a0, a2
; CHECK-NEXT: ret
; CHECK-NEXT: .LBB0_4: # %vector.ph
; CHECK-NEXT: vsetvli a0, zero, e32, m4, ta, ma
; CHECK-NEXT: vmv.s.x v8, zero
; CHECK-NEXT: vmv.v.i v12, 0
; CHECK-NEXT: vsetivli zero, 1, e32, m4, ta, ma
; CHECK-NEXT: vredsum.vs v8, v12, v8, v0.t
; CHECK-NEXT: vmv.x.s a0, v8
; CHECK-NEXT: ret
entry:
br i1 %prof.min.iters.check, label %for.body, label %vector.ph
vector.ph: ; preds = %entry
%2 = tail call i32 @llvm.vp.reduce.add.nxv8i32(i32 0, <vscale x 8 x i32> zeroinitializer, <vscale x 8 x i1> %0, i32 1)
br label %for.end
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%red.05 = phi i32 [ %3, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr i32, ptr %a, i64 %indvars.iv
%3 = load i32, ptr %arrayidx, align 4
%indvars.iv.next = add i64 %indvars.iv, 1
%exitcond.not = icmp eq i32 %n, 0
br i1 %exitcond.not, label %for.end, label %for.body
for.end: ; preds = %for.body, %vector.ph
%red.0.lcssa = phi i32 [ %2, %vector.ph ], [ %red.05, %for.body ]
ret i32 %red.0.lcssa
}
declare i32 @llvm.vp.reduce.add.nxv8i32(i32, <vscale x 8 x i32>, <vscale x 8 x i1>, i32)