[PATCH] D116918: [RISCV] Use X0 in vsetvli if AVL ≥ (2 * VLMAX)
Jianjian Guan via Phabricator via llvm-commits
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Mon Jan 10 00:40:31 PST 2022
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According to the v-spec, we always get vl = VLMAX when AVL ≥ (2 *
VLMAX), so we could use X0 in this situations.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D116918
Files:
llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
llvm/test/CodeGen/RISCV/rvv/vsetvli.ll
Index: llvm/test/CodeGen/RISCV/rvv/vsetvli.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/RISCV/rvv/vsetvli.ll
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=riscv64 -mattr=+experimental-v | FileCheck %s --check-prefixes=CHECK,DEFAULT
+; RUN: llc < %s -mtriple=riscv64 -mattr=+experimental-v -riscv-v-vector-bits-max=1024 | FileCheck %s --check-prefixes=CHECK,MAXVLEN1024
+
+declare i64 @llvm.riscv.vsetvli(
+ i64, i64, i64);
+
+define i64 @vsetvli_max() {
+; CHECK-LABEL: vsetvli_max:
+; CHECK: # %bb.0:
+; CHECK-NEXT: vsetvli a0, zero, e16, m2, ta, mu
+; CHECK-NEXT: ret
+ %vl = call i64 @llvm.riscv.vsetvli(i64 -1, i64 1, i64 1)
+ ret i64 %vl
+}
+
+define i64 @vsetvli_16384() {
+; CHECK-LABEL: vsetvli_16384:
+; CHECK: # %bb.0:
+; CHECK-NEXT: vsetvli a0, zero, e16, m2, ta, mu
+; CHECK-NEXT: ret
+ %vl = call i64 @llvm.riscv.vsetvli(i64 16384, i64 1, i64 1)
+ ret i64 %vl
+}
+
+define i64 @vsetvli_16383() {
+; DEFAULT-LABEL: vsetvli_16383:
+; DEFAULT: # %bb.0:
+; DEFAULT-NEXT: lui a0, 4
+; DEFAULT-NEXT: addiw a0, a0, -1
+; DEFAULT-NEXT: vsetvli a0, a0, e16, m2, ta, mu
+; DEFAULT-NEXT: ret
+;
+; MAXVLEN1024-LABEL: vsetvli_16383:
+; MAXVLEN1024: # %bb.0:
+; MAXVLEN1024-NEXT: vsetvli a0, zero, e16, m2, ta, mu
+; MAXVLEN1024-NEXT: ret
+ %vl = call i64 @llvm.riscv.vsetvli(i64 16383, i64 1, i64 1)
+ ret i64 %vl
+}
+
+define i64 @vsetvli_8192() {
+; CHECK-LABEL: vsetvli_8192:
+; CHECK: # %bb.0:
+; CHECK-NEXT: vsetvli a0, zero, e8, mf2, ta, mu
+; CHECK-NEXT: ret
+ %vl = call i64 @llvm.riscv.vsetvli(i64 8192, i64 0, i64 7)
+ ret i64 %vl
+}
+
+define i64 @vsetvli_8191() {
+; DEFAULT-LABEL: vsetvli_8191:
+; DEFAULT: # %bb.0:
+; DEFAULT-NEXT: lui a0, 2
+; DEFAULT-NEXT: addiw a0, a0, -1
+; DEFAULT-NEXT: vsetvli a0, a0, e8, mf2, ta, mu
+; DEFAULT-NEXT: ret
+;
+; MAXVLEN1024-LABEL: vsetvli_8191:
+; MAXVLEN1024: # %bb.0:
+; MAXVLEN1024-NEXT: vsetvli a0, zero, e8, mf2, ta, mu
+; MAXVLEN1024-NEXT: ret
+ %vl = call i64 @llvm.riscv.vsetvli(i64 8191, i64 0, i64 7)
+ ret i64 %vl
+}
Index: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -1034,6 +1034,23 @@
/* Chain */ Node->getOperand(0)));
return;
}
+
+ unsigned LMul;
+ bool Fractional;
+ std::tie(LMul, Fractional) = RISCVVType::decodeVLMUL(VLMul);
+ // Convert LMul to a fixed point value with 3 fractional bits.
+ LMul = Fractional ? (8 / LMul) : (LMul * 8);
+
+ unsigned MaxVl = Subtarget->getMaxRVVVectorSizeInBits() == 0
+ ? 65536
+ : Subtarget->getMaxRVVVectorSizeInBits();
+ unsigned MaxVLMAX = MaxVl * LMul / (8 * SEW);
+
+ // vl = VLMAX if AVL ≥ (2 * VLMAX)
+ if (AVL >= 2 * MaxVLMAX) {
+ VLOperand = CurDAG->getRegister(RISCV::X0, XLenVT);
+ Opcode = RISCV::PseudoVSETVLIX0;
+ }
}
}
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