Alexei Starovoitov 4e01a38da0 [bpf] Avoid extra pointer arithmetic for stack access
For the program like below
struct key_t {
  int pid;
  char name[16];
};
extern void test1(char *);
int test() {
  struct key_t key = {};
  test1(key.name);
  return 0;
}
For key.name, the llc/bpf may generate the below code:
  R1 = R10  // R10 is the frame pointer
  R1 += -24 // framepointer adjustment
  R1 |= 4   // R1 is then used as the first parameter of test1
OR operation is not recognized by in-kernel verifier.

This patch introduces an intermediate FI_ri instruction and
generates the following code that can be properly verified:
  R1 = R10
  R1 += -20

Patch by Yonghong Song <yhs@plumgrid.com>

llvm-svn: 249371
2015-10-06 04:00:53 +00:00
2015-09-29 06:39:09 +00:00
2015-10-06 02:13:54 +00:00
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