Hello!
Attached patch mitigates:
FAIL: gcc.dg/unroll-7.c scan-rtl-dump loop2_unroll "number of
iterations: .const_int 999999"
testsuite failure for x32 target. Loop analysis determines:
Loop 1 is simple:
simple exit 3 -> 4
infinite if: (expr_list:REG_DEP_TRUE (ne:SI (and:SI (minus:SI
(reg:SI 106 [ _13 ])
(reg:SI 105 [ ivtmp.10 ]))
(const_int 3 [0x3]))
(const_int 0 [0]))
(nil))
number of iterations: (lshiftrt:SI (plus:SI (minus:SI (reg:SI 106 [ _13 ])
(reg:SI 105 [ ivtmp.10 ]))
(const_int -4 [0xfffffffffffffffc]))
(const_int 2 [0x2]))
upper bound: 999999
likely upper bound: 999999
realistic bound: 999999
but it doesn't figure out that with (reg 105) and (reg 106), defined as:
(insn 22 19 23 2 (set (reg:SI 105 [ ivtmp.10 ])
(subreg/s/v:SI (reg/v/f:DI 110 [ a ]) 0)) 82 {*movsi_internal}
(nil))
(insn 23 22 28 2 (parallel [
(set (reg:SI 106 [ _13 ])
(plus:SI (subreg/s/v:SI (reg/v/f:DI 110 [ a ]) 0)
(const_int 4000000 [0x3d0900])))
(clobber (reg:CC 17 flags))
]) 217 {*addsi_1}
(minus:SI (reg:SI 106) ( reg:SI 105)) evaluates to (const_int
4000000). Probably, because subregs are involved.
Short of enhancing loop analysis to properly handle subregs, I propose
following testsuite patch that avoids particularities of argument
passing.
2017-04-07 Uros Bizjak <ubiz...@gmail.com>
* gcc.dg/unroll-7.c: Declare "a" as pointer to external array.
Patch was tested on x86_64 {,-m32,-mx32}.
OK for mainline?
Uros.
diff --git a/gcc/testsuite/gcc.dg/unroll-7.c b/gcc/testsuite/gcc.dg/unroll-7.c
index 70b92ba..e76d4fa 100644
--- a/gcc/testsuite/gcc.dg/unroll-7.c
+++ b/gcc/testsuite/gcc.dg/unroll-7.c
@@ -2,7 +2,9 @@
/* { dg-options "-O2 -fdump-rtl-loop2_unroll -funroll-loops" } */
/* { dg-require-effective-target int32plus } */
-int t(int *a)
+extern int *a;
+
+int t(void)
{
int i;
for (i=0;i<1000000;i++)
