This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PATCH] Fix try_combine splitting (PR target/20322)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 7 Mar 2005 11:03:26 -0500
- Subject: [PATCH] Fix try_combine splitting (PR target/20322)
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
The testcase below is miscompiled at -O2 on x86-64.
try_combine when run on (I1/I2/I3):
(insn 79 78 52 0 (parallel [
(set (reg:DI 64 [ e$a ])
(plus:DI (plus:DI (ltu:DI (reg:CC 17 flags)
(const_int 0 [0x0]))
(reg:DI 64 [ e$a ]))
(const_int 0 [0x0])))
(clobber (reg:CC 17 flags))
]) 174 {adddi3_carry_rex64} (insn_list:REG_DEP_TRUE 77 (insn_list:REG_DEP_TRUE 78 (nil)))
(expr_list:REG_DEAD (reg:CC 17 flags)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
(insn 52 79 53 0 (parallel [
(set (reg:DI 76)
(lshiftrt:DI (reg:DI 61 [ f$0 ])
(const_int 32 [0x20])))
(clobber (reg:CC 17 flags))
]) 435 {*lshrdi3_1_rex64} (nil)
(expr_list:REG_DEAD (reg:DI 61 [ f$0 ])
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
(insn 53 52 55 0 (parallel [
(set (reg:DI 60 [ e$a.6 ])
(plus:DI (reg:DI 64 [ e$a ])
(reg:DI 76)))
(clobber (reg:CC 17 flags))
]) 192 {*adddi_1_rex64} (insn_list:REG_DEP_TRUE 79 (insn_list:REG_DEP_TRUE 52 (nil)))
(expr_list:REG_DEAD (reg:DI 64 [ e$a ])
(expr_list:REG_DEAD (reg:DI 76)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))))
first merges them all into one NEWPAT:
(set (reg:DI 60 [ e$a.6 ])
(plus:DI (plus:DI (ltu:DI (reg:CC 17 flags)
(const_int 0 [0x0]))
(reg:DI 64 [ e$a ]))
(lshiftrt:DI (reg:DI 61 [ f$0 ])
(const_int 32 [0x20]))))
but because that is not recognized, find_split_point finds the LSHIFTRT
in it as desirable split point and the pattern is split into:
(set (reg:DI 76)
(lshiftrt:DI (reg:DI 61 [ f$0 ])
(const_int 32 [0x20])))
and
(set (reg:DI 60 [ e$a.6 ])
(plus:DI (plus:DI (ltu:DI (reg:CC 17 flags)
(const_int 0 [0x0]))
(reg:DI 64 [ e$a ]))
(reg:DI 76)))
But, recog_for_combine adds clobbers to the NEWI2PAT pattern
(reg:CC 17 flags) which is used by NEWPAT (and set earlier).
The following patch checks for that condition and punts.
Ok to commit to 4.0 and HEAD if testing succeeds?
It is a 4.0/4.1 regression and causes miscompilation of libcpp.
2005-03-07 Jakub Jelinek <jakub@redhat.com>
PR target/20322
* combine.c (try_combine): If recog_for_combine added CLOBBERs
to NEWI2PAT, fail to combine if they are used by NEWPAT.
* gcc.dg/20050307-1.c: New test.
--- gcc/combine.c.jj 2005-03-02 18:53:00.000000000 +0100
+++ gcc/combine.c 2005-03-07 16:41:25.624400924 +0100
@@ -2417,6 +2417,20 @@ try_combine (rtx i3, rtx i2, rtx i1, int
SUBST (*split, newdest);
i2_code_number = recog_for_combine (&newi2pat, i2, &new_i2_notes);
+ /* recog_for_combine might have added CLOBBERs to newi2pat.
+ Make sure NEWPAT does not depend on the clobbered regs. */
+ if (GET_CODE (newi2pat) == PARALLEL)
+ for (i = XVECLEN (newi2pat, 0) - 1; i >= 0; i--)
+ if (GET_CODE (XVECEXP (newi2pat, 0, i)) == CLOBBER)
+ {
+ rtx reg = XEXP (XVECEXP (newi2pat, 0, i), 0);
+ if (reg_overlap_mentioned_p (reg, newpat))
+ {
+ undo_all ();
+ return 0;
+ }
+ }
+
/* If the split point was a MULT and we didn't have one before,
don't use one now. */
if (i2_code_number >= 0 && ! (split_code == MULT && ! have_mult))
--- gcc/testsuite/gcc.dg/20050307-1.c.jj 2005-03-07 16:42:10.036508060 +0100
+++ gcc/testsuite/gcc.dg/20050307-1.c 2005-03-07 16:42:54.877537797 +0100
@@ -0,0 +1,52 @@
+/* PR target/20322 */
+
+extern void abort (void);
+
+typedef unsigned long T;
+typedef struct
+{
+ T a, b;
+ unsigned char c, d;
+} S;
+
+#define M (sizeof (T) * 4)
+
+S __attribute__((noinline))
+foo (T x, T y)
+{
+ S e;
+ T f[2], g;
+
+ e.b = (x & (~(T) 0 >> M)) * (y & (~(T) 0 >> M));
+ e.a = (x >> M) * (y >> M);
+
+ f[0] = (x & (~(T) 0 >> M)) * (y >> M);
+ f[1] = (x >> M) * (y & (~(T) 0 >> M));
+
+ g = e.b;
+ e.b += (f[0] & (~(T) 0 >> M)) << M;
+ if (e.b < g)
+ e.a++;
+
+ g = e.b;
+ e.b += (f[1] & (~(T) 0 >> M)) << M;
+ if (e.b < g)
+ e.a++;
+
+ e.a += (f[0] >> M);
+ e.a += (f[1] >> M);
+ e.c = 1;
+ e.d = 0;
+
+ return e;
+}
+
+int
+main (void)
+{
+ T x = 1UL << (M * 2 - 1);
+ S y = foo (1, x);
+ if (y.a || y.b != x || y.c != 1 || y.d)
+ abort ();
+ return 0;
+}
Jakub