[RISCV] Add tests to demonstrate bitcasted fneg/fabs dagcombines

This target-independent code won't trigger for cases such as RV32FD where
custom SelectionDAG nodes are generated. These new tests demonstrate such
cases. Additionally, float-arith.ll was updated so that fneg.s, fsgnjn.s, and
fabs.s selection patterns are actually exercised.

llvm-svn: 352199

Author: asb

llvm/test/CodeGen/RISCV/double-bitmanip-dagcombines.ll

@@ -0,0 +1,80 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32I %s
+; RUN: llc -mtriple=riscv32 -mattr=+d -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32IFD %s
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64I %s
+;
+; This file tests cases where simple floating point operations can be
+; profitably handled though bit manipulation if a soft-float ABI is being used
+; (e.g. fneg implemented by XORing the sign bit). This is typically handled in
+; DAGCombiner::visitBITCAST, but this target-independent code may not trigger
+; in cases where we perform custom legalisation (e.g. RV32IFD).
+
+; TODO: Add an appropriate target-specific DAG combine that can handle
+; RISCVISD::SplitF64/BuildPairF64 used for RV32IFD.
+
+define double @fneg(double %a) nounwind {
+; RV32I-LABEL: fneg:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    lui a2, 524288
+; RV32I-NEXT:    xor a1, a1, a2
+; RV32I-NEXT:    ret
+;
+; RV32IFD-LABEL: fneg:
+; RV32IFD:       # %bb.0:
+; RV32IFD-NEXT:    addi sp, sp, -16
+; RV32IFD-NEXT:    sw a0, 8(sp)
+; RV32IFD-NEXT:    sw a1, 12(sp)
+; RV32IFD-NEXT:    fld ft0, 8(sp)
+; RV32IFD-NEXT:    fneg.d ft0, ft0
+; RV32IFD-NEXT:    fsd ft0, 8(sp)
+; RV32IFD-NEXT:    lw a0, 8(sp)
+; RV32IFD-NEXT:    lw a1, 12(sp)
+; RV32IFD-NEXT:    addi sp, sp, 16
+; RV32IFD-NEXT:    ret
+;
+; RV64I-LABEL: fneg:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    addi a1, zero, -1
+; RV64I-NEXT:    slli a1, a1, 63
+; RV64I-NEXT:    xor a0, a0, a1
+; RV64I-NEXT:    ret
+  %1 = fneg double %a
+  ret double %1
+}
+
+declare double @llvm.fabs.f64(double)
+
+define double @fabs(double %a) nounwind {
+; RV32I-LABEL: fabs:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    lui a2, 524288
+; RV32I-NEXT:    addi a2, a2, -1
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    ret
+;
+; RV32IFD-LABEL: fabs:
+; RV32IFD:       # %bb.0:
+; RV32IFD-NEXT:    addi sp, sp, -16
+; RV32IFD-NEXT:    sw a0, 8(sp)
+; RV32IFD-NEXT:    sw a1, 12(sp)
+; RV32IFD-NEXT:    fld ft0, 8(sp)
+; RV32IFD-NEXT:    fabs.d ft0, ft0
+; RV32IFD-NEXT:    fsd ft0, 8(sp)
+; RV32IFD-NEXT:    lw a0, 8(sp)
+; RV32IFD-NEXT:    lw a1, 12(sp)
+; RV32IFD-NEXT:    addi sp, sp, 16
+; RV32IFD-NEXT:    ret
+;
+; RV64I-LABEL: fabs:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    addi a1, zero, -1
+; RV64I-NEXT:    slli a1, a1, 63
+; RV64I-NEXT:    addi a1, a1, -1
+; RV64I-NEXT:    and a0, a0, a1
+; RV64I-NEXT:    ret
+  %1 = call double @llvm.fabs.f64(double %a)
+  ret double %1
+}

llvm/test/CodeGen/RISCV/float-arith.ll

@@ -81,50 +81,58 @@ define float @fsgnj_s(float %a, float %b) nounwind {
   ret float %1
 }
 
-define float @fneg_s(float %a) nounwind {
-; TODO: doesn't test the fneg selection pattern because
-; DAGCombiner::visitBITCAST will generate a xor on the incoming integer
-; argument
+; This function performs extra work to ensure that
+; DAGCombiner::visitBITCAST doesn't replace the fneg with an xor.
+define i32 @fneg_s(float %a, float %b) nounwind {
 ; RV32IF-LABEL: fneg_s:
 ; RV32IF:       # %bb.0:
-; RV32IF-NEXT:    lui a1, 524288
-; RV32IF-NEXT:    xor a0, a0, a1
+; RV32IF-NEXT:    fmv.w.x ft0, a0
+; RV32IF-NEXT:    fadd.s ft0, ft0, ft0
+; RV32IF-NEXT:    fneg.s ft1, ft0
+; RV32IF-NEXT:    feq.s a0, ft0, ft1
 ; RV32IF-NEXT:    ret
-  %1 = fsub float -0.0, %a
-  ret float %1
+  %1 = fadd float %a, %a
+  %2 = fneg float %1
+  %3 = fcmp oeq float %1, %2
+  %4 = zext i1 %3 to i32
+  ret i32 %4
 }
 
+; This function performs extra work to ensure that
+; DAGCombiner::visitBITCAST doesn't replace the fneg with an xor.
 define float @fsgnjn_s(float %a, float %b) nounwind {
-; TODO: fsgnjn.s isn't selected because DAGCombiner::visitBITCAST will convert
-; (bitconvert (fneg x)) to a xor
 ; RV32IF-LABEL: fsgnjn_s:
 ; RV32IF:       # %bb.0:
-; RV32IF-NEXT:    lui a2, 524288
-; RV32IF-NEXT:    xor a1, a1, a2
 ; RV32IF-NEXT:    fmv.w.x ft0, a1
 ; RV32IF-NEXT:    fmv.w.x ft1, a0
-; RV32IF-NEXT:    fsgnj.s ft0, ft1, ft0
+; RV32IF-NEXT:    fadd.s ft0, ft1, ft0
+; RV32IF-NEXT:    fsgnjn.s ft0, ft1, ft0
 ; RV32IF-NEXT:    fmv.x.w a0, ft0
 ; RV32IF-NEXT:    ret
-  %1 = fsub float -0.0, %b
-  %2 = call float @llvm.copysign.f32(float %a, float %1)
-  ret float %2
+  %1 = fadd float %a, %b
+  %2 = fneg float %1
+  %3 = call float @llvm.copysign.f32(float %a, float %2)
+  ret float %3
 }
 
 declare float @llvm.fabs.f32(float)
 
-define float @fabs_s(float %a) nounwind {
-; TODO: doesn't test the fabs selection pattern because
-; DAGCombiner::visitBITCAST will generate an and on the incoming integer
-; argument
+; This function performs extra work to ensure that
+; DAGCombiner::visitBITCAST doesn't replace the fabs with an and.
+define float @fabs_s(float %a, float %b) nounwind {
 ; RV32IF-LABEL: fabs_s:
 ; RV32IF:       # %bb.0:
-; RV32IF-NEXT:    lui a1, 524288
-; RV32IF-NEXT:    addi a1, a1, -1
-; RV32IF-NEXT:    and a0, a0, a1
+; RV32IF-NEXT:    fmv.w.x ft0, a1
+; RV32IF-NEXT:    fmv.w.x ft1, a0
+; RV32IF-NEXT:    fadd.s ft0, ft1, ft0
+; RV32IF-NEXT:    fabs.s ft1, ft0
+; RV32IF-NEXT:    fadd.s ft0, ft1, ft0
+; RV32IF-NEXT:    fmv.x.w a0, ft0
 ; RV32IF-NEXT:    ret
-  %1 = call float @llvm.fabs.f32(float %a)
-  ret float %1
+  %1 = fadd float %a, %b
+  %2 = call float @llvm.fabs.f32(float %1)
+  %3 = fadd float %2, %1
+  ret float %3
 }
 
 declare float @llvm.minnum.f32(float, float)

llvm/test/CodeGen/RISCV/float-bitmanip-dagcombines.ll

@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32I %s
+; RUN: llc -mtriple=riscv32 -mattr=+f -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32I %s
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64I %s
+
+; This file tests cases where simple floating point operations can be
+; profitably handled though bit manipulation if a soft-float ABI is being used
+; (e.g. fneg implemented by XORing the sign bit). This is typically handled in
+; DAGCombiner::visitBITCAST, but this target-independent code may not trigger
+; in cases where we perform custom legalisation (e.g. RV64F).
+
+define float @fneg(float %a) nounwind {
+; RV32I-LABEL: fneg:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    lui a1, 524288
+; RV32I-NEXT:    xor a0, a0, a1
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: fneg:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    lui a1, 524288
+; RV64I-NEXT:    xor a0, a0, a1
+; RV64I-NEXT:    ret
+  %1 = fneg float %a
+  ret float %1
+}
+
+declare float @llvm.fabs.f32(float)
+
+define float @fabs(float %a) nounwind {
+; RV32I-LABEL: fabs:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    lui a1, 524288
+; RV32I-NEXT:    addi a1, a1, -1
+; RV32I-NEXT:    and a0, a0, a1
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: fabs:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    lui a1, 524288
+; RV64I-NEXT:    addiw a1, a1, -1
+; RV64I-NEXT:    and a0, a0, a1
+; RV64I-NEXT:    ret
+  %1 = call float @llvm.fabs.f32(float %a)
+  ret float %1
+}