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[RISCV] LUI used for address computation should not isAsCheapAsAMove 

A LUI instruction with flag RISCVII::MO_HI is usually used in conjunction
with ADDI, and jointly complete address computation. To bind the cost
evaluation of address computation, the LUI should not be regarded as a cheap
 move separately, which is consistent with ADDI.

In this test case, it improves the unroll-loop code that the rematerialization
of array's base address miss MachineCSE with Heuristics #1 at isProfitableToCSE.

Reviewed By: asb, frasercrmck

Differential Revision: https://reviews.llvm.org/D118216
This commit is contained in:
Haocong.Lu 2022-02-12 07:14:31 +00:00 committed by Ben Shi
parent 2e57156fea
commit 23a5073600
2 changed files with 8 additions and 14 deletions
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2
llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
View File

@ -998,6 +998,8 @@ bool RISCVInstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
return (MI.getOperand(1).isReg() &&
MI.getOperand(1).getReg() == RISCV::X0) ||
(MI.getOperand(2).isImm() && MI.getOperand(2).getImm() == 0);
case RISCV::LUI:
return MI.getOperand(1).getTargetFlags() != RISCVII::MO_HI;
}
return MI.isAsCheapAsAMove();
}

20
llvm/test/CodeGen/RISCV/unroll-loop-cse.ll
View File

@ -18,28 +18,20 @@ define signext i32 @unroll_loop_cse() {
; CHECK-NEXT: bne a3, a4, .LBB0_6
; CHECK-NEXT: # %bb.1:
; CHECK-NEXT: addi a1, a1, %lo(x)
; CHECK-NEXT: lw a1, 4(a1)
; CHECK-NEXT: lw a3, 4(a1)
; CHECK-NEXT: addi a2, a2, %lo(check)
; CHECK-NEXT: lw a2, 4(a2)
; CHECK-NEXT: bne a1, a2, .LBB0_6
; CHECK-NEXT: lw a4, 4(a2)
; CHECK-NEXT: bne a3, a4, .LBB0_6
; CHECK-NEXT: # %bb.2:
; CHECK-NEXT: lui a1, %hi(x)
; CHECK-NEXT: addi a1, a1, %lo(x)
; CHECK-NEXT: lw a3, 8(a1)
; CHECK-NEXT: lui a2, %hi(check)
; CHECK-NEXT: addi a2, a2, %lo(check)
; CHECK-NEXT: lw a4, 8(a2)
; CHECK-NEXT: bne a3, a4, .LBB0_6
; CHECK-NEXT: # %bb.3:
; CHECK-NEXT: lw a1, 12(a1)
; CHECK-NEXT: lw a2, 12(a2)
; CHECK-NEXT: bne a1, a2, .LBB0_6
; CHECK-NEXT: lw a3, 12(a1)
; CHECK-NEXT: lw a4, 12(a2)
; CHECK-NEXT: bne a3, a4, .LBB0_6
; CHECK-NEXT: # %bb.4:
; CHECK-NEXT: lui a1, %hi(x)
; CHECK-NEXT: addi a1, a1, %lo(x)
; CHECK-NEXT: lw a3, 16(a1)
; CHECK-NEXT: lui a2, %hi(check)
; CHECK-NEXT: addi a2, a2, %lo(check)
; CHECK-NEXT: lw a4, 16(a2)
; CHECK-NEXT: bne a3, a4, .LBB0_6
; CHECK-NEXT: # %bb.5: