[RISCV] Miscompile with -O3

[dtcxzyw]

Reduced test case:

#include <stdio.h>
#include <stdint.h>
int16_t g;
int32_t f;
uint32_t h;
uint64_t j = 6;
static uint64_t o(int16_t x, uint32_t *a, int16_t ac) {
  if (!x) j |= f;
  f = ac ? 7 % ac : 7;
  return j;
}
int main() {
  uint64_t v1 =  o(g, &h, 8);
  uint64_t v2 = o(v1, &h, 0);
  o(v2 >> 8, &h, 0);
  printf("%lu\n", j);
  return 0;
}

$ gcc -O0 -fsanitize=address,undefined test.c && ./a.out
7
$ bin/clang -O3 --target=riscv64-linux-gnu test.c
$ qemu-riscv64 -L /usr/riscv64-linux-gnu ./a.out
13

llvm version: ba6b2d2
qemu version: v8.2.0

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

Author: Yingwei Zheng (dtcxzyw)

Reduced test case: ``` #include <stdio.h> #include <stdint.h> int16_t g; int32_t f; uint32_t h; uint64_t j = 6; static uint64_t o(int16_t x, uint32_t *a, int16_t ac) { if (!x) j |= f; f = ac ? 7 % ac : 7; return j; } int main() { uint64_t v1 = o(g, &h, 8); uint64_t v2 = o(v1, &h, 0); o(v2 >> 8, &h, 0); printf("%lu\n", j); return 0; } ```

$ gcc -O0 -fsanitize=address,undefined test.c && ./a.out
7
$ bin/clang -O3 --target=riscv64-linux-gnu test.c
$ qemu-riscv64 -L /usr/riscv64-linux-gnu ./a.out
13

llvm version: ba6b2d2
qemu version: v8.2.0

[dtcxzyw]

It should be a middle-end bug since the disjoint flag is incorrectly inferred.

[dtcxzyw]

Reduced LLVM IR: https://alive2.llvm.org/ce/z/d5utst

define i64 @src(i64 %x) {
entry:
  %and1 = and i64 %x, 65535
  %cmp1 = icmp eq i64 %and1, 0
  %or1 = or disjoint i64 %x, 7
  %sel1 = select i1 %cmp1, i64 %or1, i64 %x
  %and2 = and i64 %sel1, 16776960
  %cmp2 = icmp eq i64 %and2, 0
  %or2 = or i64 %sel1, 7
  %sel2 = select i1 %cmp2, i64 %or2, i64 %sel1
  ret i64 %sel2
}

define i64 @tgt(i64 %x) {
  %and1 = and i64 %x, 65535
  %cmp1 = icmp eq i64 %and1, 0
  %or1 = or disjoint i64 %x, 7
  %sel1 = select i1 %cmp1, i64 %or1, i64 %x
  %and2 = and i64 %sel1, 16776960
  %cmp2 = icmp eq i64 %and2, 0
  %sel2 = select i1 %cmp2, i64 %or1, i64 %sel1
  ret i64 %sel2
}