In the case of the CALL0 ABI, values that must be retained before and
after function calls are placed in the callee-saved registers (A12
through A15) and referenced later. However, it is often the case that
the save and the reference are each only once and a simple register-
register move (the frame pointer is needed to recover the stack pointer
and must be excluded).
e.g. in the following example, if there are no other occurrences of
register A14:
;; before
; prologue {
...
s32i.n a14, sp, 16
...
; } prologue
...
mov.n a14, a6
...
call0 foo
...
mov.n a8, a14
...
; epilogue {
...
l32i.n a14, sp, 16
...
; } epilogue
It can be possible like this:
;; after
; prologue {
...
(deleted)
...
; } prologue
...
s32i.n a6, sp, 16
...
call0 foo
...
l32i.n a8, sp, 16
...
; epilogue {
...
(deleted)
...
; } epilogue
This patch introduces a new peephole2 pattern that implements the above.
gcc/ChangeLog:
* config/xtensa/xtensa.md: New peephole2 pattern that eliminates
the use of callee-saved register that saves and restores only once
for other register, by using its stack slot directly.
---
gcc/config/xtensa/xtensa.md | 60 +++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 98f3c468f8b..fc512346741 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -3024,3 +3024,63 @@ FALLTHRU:;
operands[1] = GEN_INT (imm0);
operands[2] = GEN_INT (imm1);
})
+
+(define_peephole2
+ [(set (match_operand:SI 0 "register_operand")
+ (match_operand:SI 1 "reload_operand"))]
+ "!TARGET_WINDOWED_ABI && df
+ && epilogue_contains (insn)
+ && ! call_used_or_fixed_reg_p (REGNO (operands[0]))
+ && (!frame_pointer_needed
+ || REGNO (operands[0]) != HARD_FRAME_POINTER_REGNUM)"
+ [(const_int 0)]
+{
+ rtx reg = operands[0], pattern;
+ rtx_insn *insnP = NULL, *insnS = NULL, *insnR = NULL;
+ df_ref ref;
+ rtx_insn *insn;
+ for (ref = DF_REG_DEF_CHAIN (REGNO (reg));
+ ref; ref = DF_REF_NEXT_REG (ref))
+ if (DF_REF_CLASS (ref) != DF_REF_REGULAR)
+ continue;
+ else if ((insn = DF_REF_INSN (ref)) == curr_insn)
+ continue;
+ else if (GET_CODE (pattern = PATTERN (insn)) == SET
+ && rtx_equal_p (SET_DEST (pattern), reg)
+ && REG_P (SET_SRC (pattern)))
+ {
+ if (insnS)
+ FAIL;
+ insnS = insn;
+ continue;
+ }
+ else
+ FAIL;
+ for (ref = DF_REG_USE_CHAIN (REGNO (reg));
+ ref; ref = DF_REF_NEXT_REG (ref))
+ if (DF_REF_CLASS (ref) != DF_REF_REGULAR)
+ continue;
+ else if (prologue_contains (insn = DF_REF_INSN (ref)))
+ {
+ insnP = insn;
+ continue;
+ }
+ else if (GET_CODE (pattern = PATTERN (insn)) == SET
+ && rtx_equal_p (SET_SRC (pattern), reg)
+ && REG_P (SET_DEST (pattern)))
+ {
+ if (insnR)
+ FAIL;
+ insnR = insn;
+ continue;
+ }
+ else
+ FAIL;
+ if (!insnP || !insnS || !insnR)
+ FAIL;
+ SET_DEST (PATTERN (insnS)) = copy_rtx (operands[1]);
+ df_insn_rescan (insnS);
+ SET_SRC (PATTERN (insnR)) = copy_rtx (operands[1]);
+ df_insn_rescan (insnR);
+ set_insn_deleted (insnP);
+})
--
2.30.2
