[LRA]: Exclude some hard regs for multi-reg inout reload pseudos used in asm in different mode

See gcc.c-torture/execute/20030222-1.c.  Consider the code for 32-bit (e.g. BE) target:
  int i, v; long x; x = v; asm ("" : "=r" (i) : "0" (x));
We generate the following RTL with reload insns:
  1. subreg:si(x:di, 0) = 0;
  2. subreg:si(x:di, 4) = v:si;
  3. t:di = x:di, dead x;
  4. asm ("" : "=r" (subreg:si(t:di,4)) : "0" (t:di))
  5. i:si = subreg:si(t:di,4);
If we assign hard reg of x to t, dead code elimination will remove insn #2
and we will use unitialized hard reg.  So exclude the hard reg of x for t.
We could ignore this problem for non-empty asm using all x value but it is hard to
check that the asm are expanded into insn realy using x and setting r.
The old reload pass used the same approach.

gcc/ChangeLog

	* lra-constraints.cc (match_reload): Exclude some hard regs for
	multi-reg inout reload pseudos used in asm in different mode.

0 files changed, 0 insertions, 0 deletions