[LoongArch] Add codegen support for fneg

Reference:
https://llvm.org/docs/LangRef.html#fneg-instruction

Differential Revision: https://reviews.llvm.org/D127200

Author: SixWeining

llvm/lib/Target/LoongArch/LoongArchFloat32InstrInfo.td

@@ -113,6 +113,8 @@ def FSTLE_S : FP_STORE_3R<0b00111000011101110, "fstle.s", FPR32>;
 
 /// Generic pattern classes
 
+class PatFpr<SDPatternOperator OpNode, LAInst Inst, RegisterClass RegTy>
+    : Pat<(OpNode RegTy:$fj), (Inst $fj)>;
 class PatFprFpr<SDPatternOperator OpNode, LAInst Inst, RegisterClass RegTy>
     : Pat<(OpNode RegTy:$fj, RegTy:$fk), (Inst $fj, $fk)>;
 
@@ -124,5 +126,6 @@ def : PatFprFpr<fadd, FADD_S, FPR32>;
 def : PatFprFpr<fsub, FSUB_S, FPR32>;
 def : PatFprFpr<fmul, FMUL_S, FPR32>;
 def : PatFprFpr<fdiv, FDIV_S, FPR32>;
+def : PatFpr<fneg, FNEG_S, FPR32>;
 
 } // Predicates = [HasBasicF]

llvm/lib/Target/LoongArch/LoongArchFloat64InstrInfo.td

@@ -143,5 +143,6 @@ def : PatFprFpr<fadd, FADD_D, FPR64>;
 def : PatFprFpr<fsub, FSUB_D, FPR64>;
 def : PatFprFpr<fmul, FMUL_D, FPR64>;
 def : PatFprFpr<fdiv, FDIV_D, FPR64>;
+def : PatFpr<fneg, FNEG_D, FPR64>;
 
 } // Predicates = [HasBasicD]

llvm/test/CodeGen/LoongArch/ir-instruction/fneg.ll

@@ -0,0 +1,32 @@
+; RUN: llc --mtriple=loongarch32 --mattr=+d < %s | FileCheck %s --check-prefix=LA32
+; RUN: llc --mtriple=loongarch64 --mattr=+d < %s | FileCheck %s --check-prefix=LA64
+
+;; Exercise the 'fneg' LLVM IR: https://llvm.org/docs/LangRef.html#fneg-instruction
+
+define float @fneg_s(float %x) {
+; LA32-LABEL: fneg_s:
+; LA32:       # %bb.0:
+; LA32-NEXT:    fneg.s $fa0, $fa0
+; LA32-NEXT:    jirl $zero, $ra, 0
+;
+; LA64-LABEL: fneg_s:
+; LA64:       # %bb.0:
+; LA64-NEXT:    fneg.s $fa0, $fa0
+; LA64-NEXT:    jirl $zero, $ra, 0
+  %neg = fneg float %x
+  ret float %neg
+}
+
+define double @fneg_d(double %x) {
+; LA32-LABEL: fneg_d:
+; LA32:       # %bb.0:
+; LA32-NEXT:    fneg.d $fa0, $fa0
+; LA32-NEXT:    jirl $zero, $ra, 0
+;
+; LA64-LABEL: fneg_d:
+; LA64:       # %bb.0:
+; LA64-NEXT:    fneg.d $fa0, $fa0
+; LA64-NEXT:    jirl $zero, $ra, 0
+  %neg = fneg double %x
+  ret double %neg
+}

llvm/test/CodeGen/LoongArch/ir-instruction/fsub.ll

@@ -30,3 +30,31 @@ define double @fsub_d(double %x, double %y) {
   %sub = fsub double %x, %y
   ret double %sub
 }
+
+define float @fneg_s(float %x) {
+; LA32-LABEL: fneg_s:
+; LA32:       # %bb.0:
+; LA32-NEXT:    fneg.s $fa0, $fa0
+; LA32-NEXT:    jirl $zero, $ra, 0
+;
+; LA64-LABEL: fneg_s:
+; LA64:       # %bb.0:
+; LA64-NEXT:    fneg.s $fa0, $fa0
+; LA64-NEXT:    jirl $zero, $ra, 0
+    %res = fsub float -0.0, %x
+    ret float %res
+}
+
+define double @fneg_d(double %x) {
+; LA32-LABEL: fneg_d:
+; LA32:       # %bb.0:
+; LA32-NEXT:    fneg.d $fa0, $fa0
+; LA32-NEXT:    jirl $zero, $ra, 0
+;
+; LA64-LABEL: fneg_d:
+; LA64:       # %bb.0:
+; LA64-NEXT:    fneg.d $fa0, $fa0
+; LA64-NEXT:    jirl $zero, $ra, 0
+    %res = fsub double -0.0, %x
+    ret double %res
+}