c2e84072bd
`-riscv-fp-imm-cost` controls the threshold at which the constant pool is used for float constants rather than generating directly (typically into a GPR followed by an `fmv`). The value used for this knob indicates the number of instructions that can be used to produce the value (otherwise we fall back to the constant pool). Upping to to 3 covers a huge number of additional constants (see <https://github.com/llvm/llvm-project/issues/153402>), e.g. most whole numbers which can be generated through lui+shift+fmv. As in general we struggle with efficient code generation for constant pool accesses, reducing the number of constant pool accesses is beneficial. We are typically replacing a two-instruction sequence (which includes a load) with a three instruction sequence (two simple arithmetic operations plus a fmv), which. The CHECK prefixes for various tests had to be updated to avoid conflicts leading to check lines being dropped altogether (see <https://github.com/llvm/llvm-project/pull/159321> for a change to update_llc_test_checks to aid diagnosing this).
46 lines
1.3 KiB
LLVM
46 lines
1.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
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; RUN: llc -mtriple=riscv32 -mattr=+zfbfmin -verify-machineinstrs \
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; RUN: -target-abi ilp32f < %s | FileCheck %s
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; RUN: llc -mtriple=riscv64 -mattr=+zfbfmin -verify-machineinstrs \
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; RUN: -target-abi lp64f < %s | FileCheck %s
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define bfloat @bfloat_imm() nounwind {
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; CHECK-LABEL: bfloat_imm:
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; CHECK: # %bb.0:
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; CHECK-NEXT: lui a0, 4
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; CHECK-NEXT: addi a0, a0, 64
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; CHECK-NEXT: fmv.h.x fa0, a0
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; CHECK-NEXT: ret
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ret bfloat 3.0
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}
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define bfloat @bfloat_imm_op(bfloat %a) nounwind {
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; CHECK-LABEL: bfloat_imm_op:
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; CHECK: # %bb.0:
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; CHECK-NEXT: fcvt.s.bf16 fa5, fa0
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; CHECK-NEXT: lui a0, 260096
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; CHECK-NEXT: fmv.w.x fa4, a0
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; CHECK-NEXT: fadd.s fa5, fa5, fa4
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; CHECK-NEXT: fcvt.bf16.s fa0, fa5
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; CHECK-NEXT: ret
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%1 = fadd bfloat %a, 1.0
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ret bfloat %1
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}
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define bfloat @bfloat_zero() nounwind {
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; CHECK-LABEL: bfloat_zero:
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; CHECK: # %bb.0:
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; CHECK-NEXT: fmv.h.x fa0, zero
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; CHECK-NEXT: ret
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ret bfloat 0.0
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}
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define bfloat @bfloat_negative_zero() nounwind {
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; CHECK-LABEL: bfloat_negative_zero:
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; CHECK: # %bb.0:
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; CHECK-NEXT: lui a0, 1048568
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; CHECK-NEXT: fmv.h.x fa0, a0
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; CHECK-NEXT: ret
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ret bfloat -0.0
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}
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