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michaelmaitlandmichaelmaitland
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[RISCV][VLOPT] Set CommonVL as the largest of the users (llvm#120349)
Prior to this patch, we required that all users had the same VL in order to optimize. But as the FIXME said, we can use the largest VL to optimize, as long as we can determine what the largest is. This patch implements the FIXME.
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lines changed

2 files changed

+83
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‎llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp‎

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -973,13 +973,13 @@ bool RISCVVLOptimizer::checkUsers(const MachineOperand *&CommonVL,
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assert((!VLOp.isReg() || VLOp.getReg() != RISCV::X0) &&
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"Did not expect X0 VL");
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976-
if (!CommonVL) {
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// Use the largest VL among all the users. If we cannot determine this
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// statically, then we cannot optimize the VL.
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if (!CommonVL || RISCV::isVLKnownLE(*CommonVL, VLOp)) {
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CommonVL = &VLOp;
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LLVM_DEBUG(dbgs() << " User VL is: " << VLOp << "\n");
979-
} else if (!CommonVL->isIdenticalTo(VLOp)) {
980-
// FIXME: This check requires all users to have the same VL. We can relax
981-
// this and get the largest VL amongst all users.
982-
LLVM_DEBUG(dbgs() << " Abort because users have different VL\n");
981+
} else if (!RISCV::isVLKnownLE(VLOp, *CommonVL)) {
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LLVM_DEBUG(dbgs() << " Abort because cannot determine a common VL\n");
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CanReduceVL = false;
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break;
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}

‎llvm/test/CodeGen/RISCV/rvv/vl-opt.mir‎

Lines changed: 78 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -33,3 +33,81 @@ body: |
3333
%y:vr = PseudoVREDSUM_VS_M1_E64 $noreg, %x, $noreg, -1, 6 /* e64 */, 0 /* tu, mu */
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%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 5 /* e32 */, 0 /* tu, mu */
3535
...
36+
---
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name: use_largest_common_vl_imm_imm
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body: |
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bb.0:
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; CHECK-LABEL: name: use_largest_common_vl_imm_imm
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; CHECK: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 2, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 2, 3 /* e8 */, 0 /* tu, mu */
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%x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0
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%y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0
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%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 2, 3 /* e8 */, 0
47+
...
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---
49+
name: use_largest_common_vl_same_reg
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body: |
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bb.0:
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liveins: $x1
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; CHECK-LABEL: name: use_largest_common_vl_same_reg
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; CHECK: liveins: $x1
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; CHECK-NEXT: {{ $}}
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; CHECK-NEXT: %vl:gprnox0 = COPY $x1
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; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, %vl, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0 /* tu, mu */
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%vl:gprnox0 = COPY $x1
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%x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0
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%y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0
63+
%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0
64+
...
65+
---
66+
name: use_largest_common_vl_diff_regs
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body: |
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bb.0:
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liveins: $x1, $x2
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; CHECK-LABEL: name: use_largest_common_vl_diff_regs
71+
; CHECK: liveins: $x1, $x2
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; CHECK-NEXT: {{ $}}
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; CHECK-NEXT: %vl0:gprnox0 = COPY $x1
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; CHECK-NEXT: %vl1:gprnox0 = COPY $x2
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; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl0, 3 /* e8 */, 0 /* tu, mu */
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; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl1, 3 /* e8 */, 0 /* tu, mu */
78+
%vl0:gprnox0 = COPY $x1
79+
%vl1:gprnox0 = COPY $x2
80+
%x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0
81+
%y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl0, 3 /* e8 */, 0
82+
%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl1, 3 /* e8 */, 0
83+
...
84+
---
85+
name: use_largest_common_vl_imm_reg
86+
body: |
87+
bb.0:
88+
liveins: $x1
89+
; CHECK-LABEL: name: use_largest_common_vl_imm_reg
90+
; CHECK: liveins: $x1
91+
; CHECK-NEXT: {{ $}}
92+
; CHECK-NEXT: %vl:gprnox0 = COPY $x1
93+
; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
94+
; CHECK-NEXT: %y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0 /* tu, mu */
95+
; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
96+
%vl:gprnox0 = COPY $x1
97+
%x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0
98+
%y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, %vl, 3 /* e8 */, 0
99+
%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0
100+
...
101+
---
102+
name: use_largest_common_vl_imm_vlmax
103+
body: |
104+
bb.0:
105+
; CHECK-LABEL: name: use_largest_common_vl_imm_vlmax
106+
; CHECK: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
107+
; CHECK-NEXT: %y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
108+
; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
109+
%x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0
110+
%y:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, 1, 3 /* e8 */, 0
111+
%z:vr = PseudoVADD_VV_M1 $noreg, %x, $noreg, -1, 3 /* e8 */, 0
112+
...
113+

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