[PATCH 40/44] RISC-V: Handle FP NE operator via inversion in cond-operation expansion

["Maciej W. Rozycki" <macro@embecosm.com>]

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.
---
 gcc/config/riscv/riscv-protos.h |    3 ++-
 gcc/config/riscv/riscv.cc       |   23 +++++++++++++++--------
 gcc/config/riscv/riscv.md       |    2 +-
 3 files changed, 18 insertions(+), 10 deletions(-)

gcc-riscv-emit-float-compare-ne.diff
Index: gcc/gcc/config/riscv/riscv-protos.h
===================================================================
--- gcc.orig/gcc/config/riscv/riscv-protos.h
+++ gcc/gcc/config/riscv/riscv-protos.h
@@ -132,7 +132,8 @@ riscv_zcmp_valid_stack_adj_bytes_p (HOST
 
 #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);
Index: gcc/gcc/config/riscv/riscv.cc
===================================================================
--- gcc.orig/gcc/config/riscv/riscv.cc
+++ gcc/gcc/config/riscv/riscv.cc
@@ -3965,7 +3965,8 @@ riscv_emit_int_compare (enum rtx_code *c
 /* 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;
@@ -4029,10 +4030,15 @@ riscv_emit_float_compare (enum rtx_code
 #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:
@@ -4078,9 +4084,10 @@ riscv_expand_int_scc (rtx target, enum r
 /* 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)
@@ -4171,7 +4178,7 @@ riscv_expand_conditional_move (rtx dest,
 	    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;
 
Index: gcc/gcc/config/riscv/riscv.md
===================================================================
--- gcc.orig/gcc/config/riscv/riscv.md
+++ gcc/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;