[PATCH] RISC-V: Fix build errors with shNadd/shNadd.uw patterns in zba cost model

[Maciej W. Rozycki]

Fix a build regression from commit 04a9b554ba1a ("RISC-V: Cost model 
for zba extension."):

.../gcc/config/riscv/riscv.c: In function 'bool riscv_rtx_costs(rtx, machine_mode, int, int, int*, bool)':
.../gcc/config/riscv/riscv.c:2018:11: error: 'and' of mutually exclusive equal-tests is always 0 [-Werror]
 2018 |           && IN_RANGE (INTVAL (XEXP (XEXP (x, 0), 0)), 1, 3))
      |           ^~
.../gcc/config/riscv/riscv.c:2047:17: error: unused variable 'ashift_lhs' [-Werror=unused-variable]
 2047 |             rtx ashift_lhs = XEXP (and_lhs, 0);
      |                 ^~~~~~~~~~


by removing an incorrect REG_P check applied to a constant expression 
and getting rid of the unused variable.

	gcc/
	* config/riscv/riscv.c (riscv_rtx_costs): Remove a REG_P check 
	and an unused local variable with shNadd/shNadd.uw pattern 
	handling.
---
Hi,

 As described above and I guess almost obvious -- I gather the code was 
only verified with a `-Wno-error' build and the handling of the shNadd 
pattern has not been actually covered owing to this bug making the 
condition impossible to match.

 OK to apply then?

  Maciej
---
 gcc/config/riscv/riscv.c |    2 --
 1 file changed, 2 deletions(-)

gcc-riscv-rtx-costs-zba-shnadd.diff
Index: gcc/gcc/config/riscv/riscv.c
===================================================================
--- gcc.orig/gcc/config/riscv/riscv.c
+++ gcc/gcc/config/riscv/riscv.c
@@ -2013,7 +2013,6 @@ riscv_rtx_costs (rtx x, machine_mode mod
 	  && ((!TARGET_64BIT && (mode == SImode)) ||
 	      (TARGET_64BIT && (mode == DImode)))
 	  && (GET_CODE (XEXP (x, 0)) == ASHIFT)
-	  && REG_P (XEXP (XEXP (x, 0), 0))
 	  && CONST_INT_P (XEXP (XEXP (x, 0), 0))
 	  && IN_RANGE (INTVAL (XEXP (XEXP (x, 0), 0)), 1, 3))
 	{
@@ -2044,7 +2043,6 @@ riscv_rtx_costs (rtx x, machine_mode mod
 	    if (!CONST_INT_P (and_rhs))
 	      break;
 
-	    rtx ashift_lhs = XEXP (and_lhs, 0);
 	    rtx ashift_rhs = XEXP (and_lhs, 1);
 
 	    if (!CONST_INT_P (ashift_rhs)