http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52397
Bug #: 52397
Summary: [4.7 regression] comparison failure with Ada enabled
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: bootstrap
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ebotca...@gcc.gnu.org
Host: ia64-*-linux
Target: ia64-*-linux
Build: ia64-*-linux
We have a bootstrap comparison failure on IA-64 with Ada enabled:
Bootstrap comparison failure!
gcc/ada/uintp.o differs
make[2]: *** [compare] Error 1
This is a debug insn issue. The -fdump-final-insns diff reads:
--- uintp.s.gkd.0 2012-02-25 11:33:14.050677000 -0500
+++ uintp.s.gkd.1 2012-02-25 11:33:58.240145000 -0500
@@ -3350,7 +3350,7 @@
(unspec_volatile:DI [
(const_int 0 [0])
] UNSPECV_ALLOC))
- (use (const_int 6 [0x6]))
+ (use (const_int 5 [0x5]))
(use (const_int 8 [0x8]))
(use (const_int 2 [0x2]))
(use (const_int 0 [0]))
This happens because r117 (in5) is df_regs_ever_live_p by the time the prologue
is expanded with debug insns but isn't without debug insns.
It is referenced in a debug insns after fwprop1:
(debug_insn 111 109 5 2 (var_location:DI D#136 (reg:DI 117 in5 [ quotient+8 ]))
-1
(nil))
and eliminated after dse1:
(debug_insn 111 109 5 2 (var_location:DI D#136 (clobber (const_int 0 [0]))) -1
(nil))
The debug_insn is generated by delete_trivially_dead_insns but isn't reset in
the second phase of the same processing because the register isn't a pseudo.
Now reginfo is run between fwprop1 and dse1 so the df_hard_reg_used_p r117 is
consequently computed as being regs_ever_live by df_compute_regs_ever_live
called from reginfo_init and nothing resets this afterwards (df_analyze does
call df_compute_regs_ever_live too but with RESET to false).
Teaching df_compute_regs_ever_live to reset individual registers leads to DF
verification failures for artificial registers.
