https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82524
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vmakarov at gcc dot gnu.org
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
To me it looks like a LRA bug.
In *.ira we have:
(insn 28 27 29 2 (parallel [
(set (reg/v:SI 135 [ result ])
(ashift:SI (reg:SI 153)
(const_int 16 [0x10])))
(clobber (reg:CC 17 flags))
]) "pr82545.c":26 504 {*ashlsi3_1}
(expr_list:REG_DEAD (reg:SI 153)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
...
(insn 38 37 39 2 (parallel [
(set (zero_extract:SI (reg/v:SI 135 [ result ])
(const_int 8 [0x8])
(const_int 8 [0x8]))
(subreg:SI (plus:QI (subreg:QI (zero_extract:SI (reg:SI 159)
(const_int 8 [0x8])
(const_int 8 [0x8])) 0)
(subreg:QI (zero_extract:SI (reg:SI 163)
(const_int 8 [0x8])
(const_int 8 [0x8])) 0)) 0))
(clobber (reg:CC 17 flags))
]) "pr82545.c":27 235 {*addqi_ext_2}
(expr_list:REG_DEAD (reg:SI 163)
(expr_list:REG_DEAD (reg:SI 159)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))))
...
(insn 48 47 50 2 (set (strict_low_part (subreg:QI (reg/v:SI 135 [ result ]) 0))
(reg:QI 174)) "pr82545.c":28 97 {*movstrictqi_1}
(expr_list:REG_DEAD (reg:QI 174)
(nil)))
(insn 50 48 56 2 (parallel [
(set (reg:SI 176)
(and:SI (reg/v:SI 135 [ result ])
(const_int 16777215 [0xffffff])))
(clobber (reg:CC 17 flags))
]) "pr82545.c":30 384 {*andsi_1}
(expr_list:REG_DEAD (reg/v:SI 135 [ result ])
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
which at least to the RTL documentation is valid, if zero_extract or
strict_low_part is on the LHS, it means the rest of the original register is
preserved, just the bitfield in there is modified.
But with LRA we get:
(insn 28 27 29 2 (parallel [
(set (reg/v:SI 0 ax [orig:135 result ] [135])
(ashift:SI (reg:SI 0 ax [153])
(const_int 16 [0x10])))
(clobber (reg:CC 17 flags))
]) "pr82545.c":26 504 {*ashlsi3_1}
(nil))
...
(insn 66 37 38 2 (set (reg:SI 0 ax [159])
(reg:SI 3 bx [159])) "pr82545.c":27 82 {*movsi_internal}
(nil))
(insn 38 66 39 2 (parallel [
(set (zero_extract:SI (reg:SI 0 ax [159])
(const_int 8 [0x8])
(const_int 8 [0x8]))
(subreg:SI (plus:QI (subreg:QI (zero_extract:SI (reg:SI 0 ax
[159])
(const_int 8 [0x8])
(const_int 8 [0x8])) 0)
(subreg:QI (zero_extract:SI (reg:SI 1 dx [163])
(const_int 8 [0x8])
(const_int 8 [0x8])) 0)) 0))
(clobber (reg:CC 17 flags))
]) "pr82545.c":27 235 {*addqi_ext_2}
(nil))
...
(insn 48 47 50 2 (set (strict_low_part (reg:QI 0 ax [orig:135 result ] [135]))
(reg:QI 1 dx [174])) "pr82545.c":28 97 {*movstrictqi_1}
(nil))
(insn 50 48 56 2 (parallel [
(set (reg:SI 0 ax [176])
(and:SI (reg/v:SI 0 ax [orig:135 result ] [135])
(const_int 16777215 [0xffffff])))
(clobber (reg:CC 17 flags))
]) "pr82545.c":30 384 {*andsi_1}
(nil))
