RISC-V: Handle FP NE operator via inversion in cond-operation expansion

We have no FNE.fmt machine instructions, but we can emulate them for the
purpose of conditional-move and conditional-add operations by using the
respective FEQ.fmt instruction and then swapping the data input operands
or complementing the mask for the conditional addend respectively, so
update our handlers accordingly.

	gcc/
	* config/riscv/riscv-protos.h (riscv_expand_float_scc): Add
	`invert_ptr' parameter.
	* config/riscv/riscv.cc (riscv_emit_float_compare): Add NE
	inversion handling.
	(riscv_expand_float_scc): Pass `invert_ptr' through to
	`riscv_emit_float_compare'.
	(riscv_expand_conditional_move): Pass `&invert' to
	`riscv_expand_float_scc'.
	* config/riscv/riscv.md (add<mode>cc): Likewise.

3 files changed, 18 insertions, 10 deletions

diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-protos.h
index 0050a8b..52097fe 100644
--- a/gcc/config/riscv/riscv-protos.h
+++ b/gcc/config/riscv/riscv-protos.h
@@ -132,7 +132,8 @@ riscv_zcmp_valid_stack_adj_bytes_p (HOST_WIDE_INT, int);
 
 #ifdef RTX_CODE
 extern void riscv_expand_int_scc (rtx, enum rtx_code, rtx, rtx, bool *invert_ptr = 0);
-extern void riscv_expand_float_scc (rtx, enum rtx_code, rtx, rtx);
+extern void riscv_expand_float_scc (rtx, enum rtx_code, rtx, rtx,
+				    bool *invert_ptr = nullptr);
 extern void riscv_expand_conditional_branch (rtx, enum rtx_code, rtx, rtx);
 extern rtx riscv_emit_unary (enum rtx_code code, rtx dest, rtx x);
 extern rtx riscv_emit_binary (enum rtx_code code, rtx dest, rtx x, rtx y);
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index dc8fc3e..99e64e8 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -3994,7 +3994,8 @@ riscv_emit_int_compare (enum rtx_code *code, rtx *op0, rtx *op1,
 /* Like riscv_emit_int_compare, but for floating-point comparisons.  */
 
 static void
-riscv_emit_float_compare (enum rtx_code *code, rtx *op0, rtx *op1)
+riscv_emit_float_compare (enum rtx_code *code, rtx *op0, rtx *op1,
+			  bool *invert_ptr = nullptr)
 {
   rtx tmp0, tmp1, cmp_op0 = *op0, cmp_op1 = *op1;
   enum rtx_code fp_code = *code;
@@ -4058,10 +4059,15 @@ riscv_emit_float_compare (enum rtx_code *code, rtx *op0, rtx *op1)
 #undef UNORDERED_COMPARISON
 
     case NE:
-      *code = EQ;
-      *op0 = riscv_force_binary (word_mode, EQ, cmp_op0, cmp_op1);
-      *op1 = const0_rtx;
-      break;
+      fp_code = EQ;
+      if (invert_ptr != nullptr)
+	*invert_ptr = !*invert_ptr;
+      else
+	{
+	  cmp_op0 = riscv_force_binary (word_mode, fp_code, cmp_op0, cmp_op1);
+	  cmp_op1 = const0_rtx;
+	}
+      gcc_fallthrough ();
 
     case EQ:
     case LE:
@@ -4107,9 +4113,10 @@ riscv_expand_int_scc (rtx target, enum rtx_code code, rtx op0, rtx op1, bool *in
 /* Like riscv_expand_int_scc, but for floating-point comparisons.  */
 
 void
-riscv_expand_float_scc (rtx target, enum rtx_code code, rtx op0, rtx op1)
+riscv_expand_float_scc (rtx target, enum rtx_code code, rtx op0, rtx op1,
+			bool *invert_ptr)
 {
-  riscv_emit_float_compare (&code, &op0, &op1);
+  riscv_emit_float_compare (&code, &op0, &op1, invert_ptr);
 
   machine_mode mode = GET_MODE (target);
   if (mode != word_mode)
@@ -4200,7 +4207,7 @@ riscv_expand_conditional_move (rtx dest, rtx op, rtx cons, rtx alt)
 	    riscv_expand_int_scc (tmp, code, op0, op1, invert_ptr);
 	  else if (FLOAT_MODE_P (mode0)
 		   && fp_scc_comparison (op, GET_MODE (op)))
-	    riscv_expand_float_scc (tmp, code, op0, op1);
+	    riscv_expand_float_scc (tmp, code, op0, op1, &invert);
 	  else
 	    return false;
 
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index c4db7a7..6326def 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -2697,7 +2697,7 @@
   if (INTEGRAL_MODE_P (mode0))
     riscv_expand_int_scc (reg0, code, cmp0, cmp1, &invert);
   else if (FLOAT_MODE_P (mode0) && fp_scc_comparison (cmp, GET_MODE (cmp)))
-    riscv_expand_float_scc (reg0, code, cmp0, cmp1);
+    riscv_expand_float_scc (reg0, code, cmp0, cmp1, &invert);
   else
     FAIL;