sim/riscv: fix JALR instruction simulation

Fix 32bit 'jalr rd,ra,imm' integer instruction, where RD was written
before using it to calculate destination address.

This commit also improves testutils.inc for riscv; make use of
pushsection and popsection when adding things to .data, and setup the
%gp global pointer register within the 'start' macro.

Approved-By: Andrew Burgess <[email protected]>

Author: JaydeepIMG

sim/riscv/sim-main.c

@@ -449,8 +449,8 @@ execute_i (SIM_CPU *cpu, unsigned_word iw, const struct riscv_opcode *op)
       break;
     case MATCH_JALR:
       TRACE_INSN (cpu, "jalr %s, %s, %" PRIiTW ";", rd_name, rs1_name, i_imm);
-      store_rd (cpu, rd, riscv_cpu->pc + 4);
       pc = riscv_cpu->regs[rs1] + i_imm;
+      store_rd (cpu, rd, riscv_cpu->pc + 4);
       TRACE_BRANCH (cpu, "to %#" PRIxTW, pc);
       break;
 

sim/testsuite/riscv/jalr.s

@@ -0,0 +1,22 @@
+# Basic jalr tests.
+# mach: riscv
+
+.include "testutils.inc"
+
+	start
+
+	# Load desination into register a0.
+	la	a0, good_dest
+
+	# Jump to the destination in a0.
+	jalr	a0, a0, 0
+
+	# If we write destination into a0 before reading it in order
+	# to jump, we might end up here.
+bad_dest:
+	fail
+
+	# We should end up here.
+good_dest:
+	pass
+	fail

sim/testsuite/riscv/testutils.inc

@@ -21,8 +21,9 @@
 	# Trigger OS trap.
 	ecall;
 	exit 0;
-	.data
+	.pushsection .data
 	1: .asciz "pass\n"
+	.popsection
 	.endm
 
 # MACRO: fail
@@ -33,14 +34,15 @@
 	# Use stdout.
 	li a0, 1;
 	# Point to the string.
-	lla a1, 1f;
+	la a1, 1f;
 	# Number of bytes to write.
 	li a2, 5;
 	# Trigger OS trap.
 	ecall;
 	exit 0;
-	.data
+	.pushsection .data
 	1: .asciz "fail\n"
+	.popsection
 	.endm
 
 # MACRO: start
@@ -49,4 +51,8 @@
 	.text
 .global _start
 _start:
+	.option push
+	.option norelax
+	lla gp, __global_pointer$
+	.option pop
 	.endm