address misaligned exception seen on ld for rs1 == rd

[kumaransvyoma]

ld misaligned with spike for aligned address:

ld_test.zip

• The test does an ld on aligned address 0x80002000. The test when run with different register operands does not show any misaligned address exception but using the same address with rs1 == rd generates an exception

**test:**
  la s2,rvtest_data
diff_reg:
  ld s4,0(s2)
same_reg:
  ld s2,0(s2)

**disassembly:**
80000124:   ee090913            add s2,s2,-288 # 80002000 <rvtest_data_begin>
80000128 <diff_reg>:
80000128:   00093a03            .insn   4, 0x00093a03
8000012c <same_reg>:
8000012c:   00093903            .insn   4, 0x00093903

• For example, in the ld s2, 0(s2) case as seen above with s2 = 0x80002000 (aligned), data from mem location s2 updates the s2 without any exception. Now for the updation of s3 register, instead of taking the old s2 (aligned); the spike takes the new s2 (from test memory) and generates an exception.
• When the test is modified to have the test memory to also have an aligned address for the new s2 value, the exception is not seen. if the 2 loads to the s2, s3 has to happen atomically with the same address and address+4, then the spike has to be fixed
• Sail run passes without any issue for this case

To reproduce the issue

# compile
clang -march=rv32izilsd          -static -mcmodel=medany -fvisibility=hidden -nostdlib -nostartfiles  -T ./env/link.ld      -I ./env -mabi=ilp32  ./ld-01.S -o my.elf -DTEST_CASE_1=True -DXLEN=32
# To execute 
spike --log-commits --log spike.log  --isa=rv32iZilsd  my.elf

[christian-herber-nxp]

should be fixed with 9c7b983

[lavanyajagan]

fix verified