[llvm] [RISCV] Fold vmv.s.x into load from stack (PR #109774)
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Tue Sep 24 02:28:10 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Luke Lau (lukel97)
<details>
<summary>Changes</summary>
If a vector is reloaded from the stack to be used in vmv.s.x, we can tell foldMemoryOperandImpl to fold it into a scalar load.
If XLEN < SEW then this currently just bails. I couldn't think of a way to express a vmv.s.x that truncates in LLVM IR.
---
Full diff: https://github.com/llvm/llvm-project/pull/109774.diff
2 Files Affected:
- (modified) llvm/lib/Target/RISCV/RISCVInstrInfo.cpp (+23)
- (added) llvm/test/CodeGen/RISCV/rvv/stack-folding.ll (+162)
``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
index 41f93fde17d329..8210f756f3a249 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -763,6 +763,29 @@ MachineInstr *RISCVInstrInfo::foldMemoryOperandImpl(
LoadOpc = RISCV::LBU;
break;
}
+ if (RISCV::getRVVMCOpcode(MI.getOpcode()) == RISCV::VMV_X_S) {
+ unsigned Log2SEW =
+ MI.getOperand(RISCVII::getSEWOpNum(MI.getDesc())).getImm();
+ if (STI.getXLen() < (1 << Log2SEW))
+ return nullptr;
+ switch (Log2SEW) {
+ case 3:
+ LoadOpc = RISCV::LB;
+ break;
+ case 4:
+ LoadOpc = RISCV::LH;
+ break;
+ case 5:
+ LoadOpc = RISCV::LW;
+ break;
+ case 6:
+ LoadOpc = RISCV::LD;
+ break;
+ default:
+ llvm_unreachable("Unexpected SEW");
+ }
+ break;
+ }
return nullptr;
case RISCV::SEXT_H:
LoadOpc = RISCV::LH;
diff --git a/llvm/test/CodeGen/RISCV/rvv/stack-folding.ll b/llvm/test/CodeGen/RISCV/rvv/stack-folding.ll
new file mode 100644
index 00000000000000..4771d7fe6ec92b
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/rvv/stack-folding.ll
@@ -0,0 +1,162 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=riscv32 -mattr=+v -verify-machineinstrs | FileCheck --check-prefixes=CHECK,RV32 %s
+; RUN: llc < %s -mtriple=riscv64 -mattr=+v -verify-machineinstrs | FileCheck --check-prefixes=CHECK,RV64 %s
+
+define i64 @i64(<vscale x 1 x i64> %v, i1 %c) {
+; RV32-LABEL: i64:
+; RV32: # %bb.0:
+; RV32-NEXT: addi sp, sp, -16
+; RV32-NEXT: .cfi_def_cfa_offset 16
+; RV32-NEXT: csrr a1, vlenb
+; RV32-NEXT: slli a1, a1, 1
+; RV32-NEXT: sub sp, sp, a1
+; RV32-NEXT: .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x02, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 2 * vlenb
+; RV32-NEXT: addi a1, sp, 16
+; RV32-NEXT: vs1r.v v8, (a1) # Unknown-size Folded Spill
+; RV32-NEXT: andi a0, a0, 1
+; RV32-NEXT: #APP
+; RV32-NEXT: #NO_APP
+; RV32-NEXT: beqz a0, .LBB0_2
+; RV32-NEXT: # %bb.1: # %truebb
+; RV32-NEXT: li a0, 32
+; RV32-NEXT: vl1r.v v9, (a1) # Unknown-size Folded Reload
+; RV32-NEXT: vsetivli zero, 1, e64, m1, ta, ma
+; RV32-NEXT: vsrl.vx v8, v9, a0
+; RV32-NEXT: vmv.x.s a1, v8
+; RV32-NEXT: vmv.x.s a0, v9
+; RV32-NEXT: j .LBB0_3
+; RV32-NEXT: .LBB0_2: # %falsebb
+; RV32-NEXT: li a1, 0
+; RV32-NEXT: .LBB0_3: # %falsebb
+; RV32-NEXT: csrr a2, vlenb
+; RV32-NEXT: slli a2, a2, 1
+; RV32-NEXT: add sp, sp, a2
+; RV32-NEXT: addi sp, sp, 16
+; RV32-NEXT: ret
+;
+; RV64-LABEL: i64:
+; RV64: # %bb.0:
+; RV64-NEXT: addi sp, sp, -16
+; RV64-NEXT: .cfi_def_cfa_offset 16
+; RV64-NEXT: csrr a1, vlenb
+; RV64-NEXT: slli a1, a1, 1
+; RV64-NEXT: sub sp, sp, a1
+; RV64-NEXT: .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x02, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 2 * vlenb
+; RV64-NEXT: addi a1, sp, 16
+; RV64-NEXT: vs1r.v v8, (a1) # Unknown-size Folded Spill
+; RV64-NEXT: andi a0, a0, 1
+; RV64-NEXT: #APP
+; RV64-NEXT: #NO_APP
+; RV64-NEXT: beqz a0, .LBB0_2
+; RV64-NEXT: # %bb.1: # %truebb
+; RV64-NEXT: ld a0, 16(sp) # 8-byte Folded Reload
+; RV64-NEXT: .LBB0_2: # %falsebb
+; RV64-NEXT: csrr a1, vlenb
+; RV64-NEXT: slli a1, a1, 1
+; RV64-NEXT: add sp, sp, a1
+; RV64-NEXT: addi sp, sp, 16
+; RV64-NEXT: ret
+ tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14},~{v15},~{v16},~{v17},~{v18},~{v19},~{v20},~{v21},~{v22},~{v23},~{v24},~{v25},~{v26},~{v27},~{v28},~{v29},~{v30},~{v31}"()
+ br i1 %c, label %truebb, label %falsebb
+truebb:
+ %x = extractelement <vscale x 1 x i64> %v, i32 0
+ ret i64 %x
+falsebb:
+ ret i64 0
+}
+
+define i32 @i32(<vscale x 2 x i32> %v, i1 %c) {
+; CHECK-LABEL: i32:
+; CHECK: # %bb.0:
+; CHECK-NEXT: addi sp, sp, -16
+; CHECK-NEXT: .cfi_def_cfa_offset 16
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: sub sp, sp, a1
+; CHECK-NEXT: .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x02, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 2 * vlenb
+; CHECK-NEXT: addi a1, sp, 16
+; CHECK-NEXT: vs1r.v v8, (a1) # Unknown-size Folded Spill
+; CHECK-NEXT: andi a0, a0, 1
+; CHECK-NEXT: #APP
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: beqz a0, .LBB1_2
+; CHECK-NEXT: # %bb.1: # %truebb
+; CHECK-NEXT: lw a0, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT: .LBB1_2: # %falsebb
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: add sp, sp, a1
+; CHECK-NEXT: addi sp, sp, 16
+; CHECK-NEXT: ret
+ tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14},~{v15},~{v16},~{v17},~{v18},~{v19},~{v20},~{v21},~{v22},~{v23},~{v24},~{v25},~{v26},~{v27},~{v28},~{v29},~{v30},~{v31}"()
+ br i1 %c, label %truebb, label %falsebb
+truebb:
+ %x = extractelement <vscale x 2 x i32> %v, i32 0
+ ret i32 %x
+falsebb:
+ ret i32 0
+}
+
+define i16 @i16(<vscale x 4 x i16> %v, i1 %c) {
+; CHECK-LABEL: i16:
+; CHECK: # %bb.0:
+; CHECK-NEXT: addi sp, sp, -16
+; CHECK-NEXT: .cfi_def_cfa_offset 16
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: sub sp, sp, a1
+; CHECK-NEXT: .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x02, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 2 * vlenb
+; CHECK-NEXT: addi a1, sp, 16
+; CHECK-NEXT: vs1r.v v8, (a1) # Unknown-size Folded Spill
+; CHECK-NEXT: andi a0, a0, 1
+; CHECK-NEXT: #APP
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: beqz a0, .LBB2_2
+; CHECK-NEXT: # %bb.1: # %truebb
+; CHECK-NEXT: lh a0, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT: .LBB2_2: # %falsebb
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: add sp, sp, a1
+; CHECK-NEXT: addi sp, sp, 16
+; CHECK-NEXT: ret
+ tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14},~{v15},~{v16},~{v17},~{v18},~{v19},~{v20},~{v21},~{v22},~{v23},~{v24},~{v25},~{v26},~{v27},~{v28},~{v29},~{v30},~{v31}"()
+ br i1 %c, label %truebb, label %falsebb
+truebb:
+ %x = extractelement <vscale x 4 x i16> %v, i32 0
+ ret i16 %x
+falsebb:
+ ret i16 0
+}
+
+define i8 @i8(<vscale x 8 x i8> %v, i1 %c) {
+; CHECK-LABEL: i8:
+; CHECK: # %bb.0:
+; CHECK-NEXT: addi sp, sp, -16
+; CHECK-NEXT: .cfi_def_cfa_offset 16
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: sub sp, sp, a1
+; CHECK-NEXT: .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x02, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 2 * vlenb
+; CHECK-NEXT: addi a1, sp, 16
+; CHECK-NEXT: vs1r.v v8, (a1) # Unknown-size Folded Spill
+; CHECK-NEXT: andi a0, a0, 1
+; CHECK-NEXT: #APP
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: beqz a0, .LBB3_2
+; CHECK-NEXT: # %bb.1: # %truebb
+; CHECK-NEXT: lb a0, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT: .LBB3_2: # %falsebb
+; CHECK-NEXT: csrr a1, vlenb
+; CHECK-NEXT: slli a1, a1, 1
+; CHECK-NEXT: add sp, sp, a1
+; CHECK-NEXT: addi sp, sp, 16
+; CHECK-NEXT: ret
+ tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14},~{v15},~{v16},~{v17},~{v18},~{v19},~{v20},~{v21},~{v22},~{v23},~{v24},~{v25},~{v26},~{v27},~{v28},~{v29},~{v30},~{v31}"()
+ br i1 %c, label %truebb, label %falsebb
+truebb:
+ %x = extractelement <vscale x 8 x i8> %v, i32 0
+ ret i8 %x
+falsebb:
+ ret i8 0
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/109774
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