https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107250
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Component|tree-optimization |target
Version|unknown |13.0
Last reconfirmed| |2022-10-14
Status|UNCONFIRMED |NEW
Target| |x86_64-*-*
Ever confirmed|0 |1
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The question is _why_ we generate worse code ... looks like pro/epilogue
generation differs:
@@ -11,15 +11,19 @@
Attempting shrink-wrapping optimization.
Block 2 needs prologue due to insn 2:
(insn 2 4 3 2 (set (reg/v/f:DI 3 bx [orig:84 f ] [84])
- (reg:DI 5 di [87])) "t.c":4:23 82 {*movdi_internal}
+ (reg:DI 5 di [86])) "t.c":4:23 82 {*movdi_internal}
(nil))
After wrapping required blocks, PRO is now 2
Avoiding non-duplicatable blocks, PRO is now 2
Bumping back to anticipatable blocks, PRO is now 2
...
1: NOTE_INSN_DELETED
4: NOTE_INSN_BASIC_BLOCK 2
- 18: [--sp:DI]=bx:DI
- 19: NOTE_INSN_PROLOGUE_END
+ 18: [--sp:DI]=bp:DI
+ 19: [--sp:DI]=bx:DI
+ 20: {sp:DI=sp:DI-0x8;clobber flags:CC;clobber [scratch];}
+ REG_CFA_ADJUST_CFA sp:DI=sp:DI-0x8
+ 21: NOTE_INSN_PROLOGUE_END
2: bx:DI=di:DI
3: NOTE_INSN_FUNCTION_BEG
- 6: di:DI=0x8
- 7: ax:DI=call [`malloc'] argc:0
+ 6: bp:DI=[bx:DI]
+ 7: di:DI=0x8
+ 8: ax:DI=call [`malloc'] argc:0
REG_CALL_DECL `malloc'
REG_EH_REGION 0
- 10: dx:DI=[bx:DI]
- REG_EQUIV [bx:DI]
- 11: [ax:DI]=dx:DI
+ 11: [ax:DI]=bp:DI
12: [bx:DI]=ax:DI
- 20: NOTE_INSN_EPILOGUE_BEG
- 21: bx:DI=[sp:DI++]
+ 22: NOTE_INSN_EPILOGUE_BEG
+ 23: {sp:DI=sp:DI+0x8;clobber flags:CC;clobber [scratch];}
REG_CFA_ADJUST_CFA sp:DI=sp:DI+0x8
- 22: simple_return
- 25: barrier
+ 24: bx:DI=[sp:DI++]
+ REG_CFA_ADJUST_CFA sp:DI=sp:DI+0x8
+ 25: bp:DI=[sp:DI++]
+ REG_CFA_ADJUST_CFA sp:DI=sp:DI+0x8
+ 26: simple_return
+ 29: barrier
17: NOTE_INSN_DELETED
