[llvm] [LLVM][RISCV][BF16] Support Inline ASM for the bf16 type. (PR #80118)
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Wed Jan 31 00:47:26 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Chuan-Yue Yuan (circYuan)
<details>
<summary>Changes</summary>
This patch makes the RISCV-V asm constraint `f` recognize the bfloat type.
---
Full diff: https://github.com/llvm/llvm-project/pull/80118.diff
3 Files Affected:
- (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (+12-1)
- (modified) llvm/lib/Target/RISCV/RISCVISelLowering.cpp (+7)
- (added) llvm/test/CodeGen/RISCV/inline-asm-f-constraint-bf16.ll (+77)
``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 5ce1013f30fd1..7342e7bcba1f2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -9105,7 +9105,7 @@ getRegistersForValue(SelectionDAG &DAG, const SDLoc &DL,
// Get the actual register value type. This is important, because the user
// may have asked for (e.g.) the AX register in i32 type. We need to
// remember that AX is actually i16 to get the right extension.
- const MVT RegVT = *TRI.legalclasstypes_begin(*RC);
+ MVT RegVT = *TRI.legalclasstypes_begin(*RC);
if (OpInfo.ConstraintVT != MVT::Other && RegVT != MVT::Untyped) {
// If this is an FP operand in an integer register (or visa versa), or more
@@ -9139,6 +9139,17 @@ getRegistersForValue(SelectionDAG &DAG, const SDLoc &DL,
DAG.getNode(ISD::BITCAST, DL, VT, OpInfo.CallOperand);
OpInfo.ConstraintVT = VT;
}
+ // If the RegisterClass contains more than one types like RISCV
+ // FPR16RegClass which has [f16, bf16], We should check if the
+ // OpInfo.ConstraintVT can directly be assigned to the RegVT.
+ } else if ((OpInfo.Type == InlineAsm::isOutput ||
+ OpInfo.Type == InlineAsm::isInput) &&
+ TRI.isTypeLegalForClass(*RC, OpInfo.ConstraintVT)) {
+ if (RegVT != OpInfo.ConstraintVT &&
+ RegVT.getSizeInBits() == OpInfo.ConstraintVT.getSizeInBits() &&
+ RegVT.isFloatingPoint() && OpInfo.ConstraintVT.isFloatingPoint()) {
+ RegVT = OpInfo.ConstraintVT;
+ }
}
}
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index b8994e7b7bdb2..7a6e41ab7fee3 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -19225,6 +19225,8 @@ RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
return std::make_pair(0U, &RISCV::GPRPairRegClass);
return std::make_pair(0U, &RISCV::GPRNoX0RegClass);
case 'f':
+ if (Subtarget.hasStdExtZfbfmin() && VT == MVT::bf16)
+ return std::make_pair(0U, &RISCV::FPR16RegClass);
if (Subtarget.hasStdExtZfhmin() && VT == MVT::f16)
return std::make_pair(0U, &RISCV::FPR16RegClass);
if (Subtarget.hasStdExtF() && VT == MVT::f32)
@@ -19343,6 +19345,11 @@ RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
unsigned HReg = RISCV::F0_H + RegNo;
return std::make_pair(HReg, &RISCV::FPR16RegClass);
}
+ if (Subtarget.hasStdExtZfbfmin() && VT == MVT::bf16) {
+ unsigned RegNo = FReg - RISCV::F0_F;
+ unsigned HReg = RISCV::F0_H + RegNo;
+ return std::make_pair(HReg, &RISCV::FPR16RegClass);
+ }
}
}
diff --git a/llvm/test/CodeGen/RISCV/inline-asm-f-constraint-bf16.ll b/llvm/test/CodeGen/RISCV/inline-asm-f-constraint-bf16.ll
new file mode 100644
index 0000000000000..a496e2fea173e
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/inline-asm-f-constraint-bf16.ll
@@ -0,0 +1,77 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=riscv32 -mattr=+f,+experimental-zfbfmin -target-abi=ilp32 -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=RV32F %s
+; RUN: llc -mtriple=riscv64 -mattr=+f,+experimental-zfbfmin -target-abi=lp64 -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=RV64F %s
+; RUN: llc -mtriple=riscv32 -mattr=+d,+experimental-zfbfmin -target-abi=ilp32 -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=RV32F %s
+; RUN: llc -mtriple=riscv64 -mattr=+d,+experimental-zfbfmin -target-abi=lp64 -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=RV64F %s
+
+ at gf = external global float
+
+define float @constraint_f_float(bfloat %a) nounwind {
+; RV32F-LABEL: constraint_f_float:
+; RV32F: # %bb.0:
+; RV32F-NEXT: fmv.h.x fa5, a0
+; RV32F-NEXT: #APP
+; RV32F-NEXT: fcvt.s.bf16 fa5, fa5
+; RV32F-NEXT: #NO_APP
+; RV32F-NEXT: fmv.x.w a0, fa5
+; RV32F-NEXT: ret
+;
+; RV64F-LABEL: constraint_f_float:
+; RV64F: # %bb.0:
+; RV64F-NEXT: fmv.h.x fa5, a0
+; RV64F-NEXT: #APP
+; RV64F-NEXT: fcvt.s.bf16 fa5, fa5
+; RV64F-NEXT: #NO_APP
+; RV64F-NEXT: fmv.x.w a0, fa5
+; RV64F-NEXT: ret
+ %1 = load float, ptr @gf
+ %2 = tail call float asm "fcvt.s.bf16 $0, $1", "=f,f"(bfloat %a)
+ ret float %2
+}
+
+define float @constraint_f_float_abi_name(bfloat %a) nounwind {
+; RV32F-LABEL: constraint_f_float_abi_name:
+; RV32F: # %bb.0:
+; RV32F-NEXT: fmv.h.x fa0, a0
+; RV32F-NEXT: #APP
+; RV32F-NEXT: fcvt.s.bf16 ft0, fa0
+; RV32F-NEXT: #NO_APP
+; RV32F-NEXT: fmv.x.w a0, ft0
+; RV32F-NEXT: ret
+;
+; RV64F-LABEL: constraint_f_float_abi_name:
+; RV64F: # %bb.0:
+; RV64F-NEXT: fmv.h.x fa0, a0
+; RV64F-NEXT: #APP
+; RV64F-NEXT: fcvt.s.bf16 ft0, fa0
+; RV64F-NEXT: #NO_APP
+; RV64F-NEXT: fmv.x.w a0, ft0
+; RV64F-NEXT: ret
+ %1 = load float, ptr @gf
+ %2 = tail call float asm "fcvt.s.bf16 $0, $1", "={ft0},{fa0}"(bfloat %a)
+ ret float %2
+}
+
+define bfloat @constraint_gpr(bfloat %x) {
+; RV32F-LABEL: constraint_gpr:
+; RV32F: # %bb.0:
+; RV32F-NEXT: .cfi_def_cfa_offset 0
+; RV32F-NEXT: #APP
+; RV32F-NEXT: mv a0, a0
+; RV32F-NEXT: #NO_APP
+; RV32F-NEXT: ret
+;
+; RV64F-LABEL: constraint_gpr:
+; RV64F: # %bb.0:
+; RV64F-NEXT: .cfi_def_cfa_offset 0
+; RV64F-NEXT: #APP
+; RV64F-NEXT: mv a0, a0
+; RV64F-NEXT: #NO_APP
+; RV64F-NEXT: ret
+ %1 = tail call bfloat asm sideeffect alignstack "mv $0, $1", "={x10},{x10}"(bfloat %x)
+ ret bfloat %1
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/80118
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