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| author | Vladimir N. Makarov <vmakarov@redhat.com> | 2023-04-20 10:02:13 -0400 |
|---|---|---|
| committer | Vladimir N. Makarov <vmakarov@redhat.com> | 2023-04-20 11:05:33 -0400 |
| commit | 1d2aa9a8cb8fd078af930347392cfdfc14e1551c (patch) | |
| tree | da96939f6410edf0c7897fea85a6004fe2ad1300 | |
| parent | cae48a9d80790dcde6ae86122546c89a00d8bb4f (diff) | |
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[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.
| -rw-r--r-- | gcc/lra-constraints.cc | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index b231cb6..4dc2d70 100644 --- a/gcc/lra-constraints.cc +++ b/gcc/lra-constraints.cc @@ -1022,6 +1022,34 @@ match_reload (signed char out, signed char *ins, signed char *outs, are ordered. */ if (partial_subreg_p (outmode, inmode)) { + bool asm_p = asm_noperands (PATTERN (curr_insn)) >= 0; + int hr; + HARD_REG_SET temp_hard_reg_set; + + if (asm_p && (hr = get_hard_regno (out_rtx)) >= 0 + && hard_regno_nregs (hr, inmode) > 1) + { + /* 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. */ + CLEAR_HARD_REG_SET (temp_hard_reg_set); + if (exclude_start_hard_regs != NULL) + temp_hard_reg_set = *exclude_start_hard_regs; + SET_HARD_REG_BIT (temp_hard_reg_set, hr); + exclude_start_hard_regs = &temp_hard_reg_set; + } reg = new_in_reg = lra_create_new_reg_with_unique_value (inmode, in_rtx, goal_class, exclude_start_hard_regs, |