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Clobber the condition code in the bfin doloop patterns 

Per Aldy's excellent, but tough to follow analysis in PR 103226, this patch
fixes the bfin-elf regression.

In simplest terms the doloop patterns on this port may clobber the condition
code register, but they do not expose that until after register allocation.
That would be fine, except that other patterns have exposed CC earlier.  As
a result the dataflow, particularly for CC, is incorrect.

This leads the register allocators to assume that a value in CC outside the
loop is still valid inside the loop when in fact, the value has been
clobbered.  This is what caused pr80974 to start failing.

With this fix, not only do we fix the pr80974 regression, but we fix ~20
other execution failures in the port.  It also reduces test time for the
port from ~90 minutes to ~60 minutes.

	PR tree-optimization/103226
gcc/
	* config/bfin/bfin.md (doloop pattern, splitter and expander): Clobber
	CC.
This commit is contained in:
Jeff Law 2021-11-20 11:20:07 -05:00
parent 5f40d34b6d
commit 7950c96ca6
1 changed files with 6 additions and 3 deletions
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9
gcc/config/bfin/bfin.md
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@ -1959,7 +1959,8 @@
(plus:SI (match_dup 0)
(const_int -1)))
(unspec [(const_int 0)] UNSPEC_LSETUP_END)
(clobber (match_dup 2))])] ; match_scratch
(clobber (match_dup 2))
(clobber (reg:BI REG_CC))])] ; match_scratch
""
{
/* The loop optimizer doesn't check the predicates... */
@ -1979,7 +1980,8 @@
(plus (match_dup 2)
(const_int -1)))
(unspec [(const_int 0)] UNSPEC_LSETUP_END)
(clobber (match_scratch:SI 3 "=X,&r,&r"))]
(clobber (match_scratch:SI 3 "=X,&r,&r"))
(clobber (reg:BI REG_CC))]
""
"@
/* loop end %0 %l1 */
@ -1997,7 +1999,8 @@
(plus (match_dup 0)
(const_int -1)))
(unspec [(const_int 0)] UNSPEC_LSETUP_END)
(clobber (match_scratch:SI 2))]
(clobber (match_scratch:SI 2))
(clobber (reg:BI REG_CC))]
"memory_operand (operands[0], SImode) || splitting_loops"
[(set (match_dup 2) (match_dup 0))
(set (match_dup 2) (plus:SI (match_dup 2) (const_int -1)))