new file mode 100644
@@ -0,0 +1,19 @@
+! { dg-do compile }
+! { dg-options "-fdump-tree-optimized-blocks -O3" }
+
+SUBROUTINE S42(a,b,c,N)
+ IMPLICIT NONE
+ integer :: N
+ real*8 :: a(N),b(N),c(N),tmp,tmp2,tmp4
+ real*8, parameter :: p=1.0D0/3.0D0
+ integer :: i
+ c=0.0D0
+ DO i=1,N
+ tmp=a(i)**p ! could even be done with a cube root
+ tmp2=tmp*tmp
+ tmp4=tmp2*tmp2
+ b(i)=b(i)+tmp4
+ c(i)=c(i)+tmp2
+ ENDDO
+END SUBROUTINE
+! { dg-final { scan-tree-dump-not "Invalid sum" "optimized" } }
@@ -422,6 +422,7 @@ ch_base::copy_headers (function *fun)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Loop %d never loops.\n", loop->num);
+ scale_loop_profile (loop, profile_probability::always (), 0);
loops_to_unloop.safe_push (loop);
loops_to_unloop_nunroll.safe_push (0);
continue;
@@ -666,6 +667,7 @@ ch_base::copy_headers (function *fun)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Loop %d no longer loops.\n", loop->num);
+ scale_loop_profile (loop, profile_probability::always (), 0);
loops_to_unloop.safe_push (loop);
loops_to_unloop_nunroll.safe_push (0);
}
@@ -906,6 +906,10 @@ try_unroll_loop_completely (class loop *loop,
if (may_be_zero)
bitmap_clear_bit (wont_exit, 1);
+ /* If loop was originally estimated to iterate too many times,
+ reduce the profile to avoid new profile inconsistencies. */
+ scale_loop_profile (loop, profile_probability::always (), n_unroll);
+
if (!gimple_duplicate_loop_body_to_header_edge (
loop, loop_preheader_edge (loop), n_unroll, wont_exit, exit,
&edges_to_remove,
@@ -919,6 +923,8 @@ try_unroll_loop_completely (class loop *loop,
free_original_copy_tables ();
}
+ else
+ scale_loop_profile (loop, profile_probability::always (), 0);
/* Remove the conditional from the last copy of the loop. */
if (edge_to_cancel)
Hi, this patch makes loop-ch and loop unrolling to fix profile in case the loop is known to not iterate at all (or iterate few times) while profile claims it iterates more. While this is kind of symptomatic fix, it is best we can do incase profile was originally esitmated incorrectly. In the testcase the problematic loop is produced by vectorizer and I think vectorizer should know and account into its costs that vectorizer loop and/or epilogue is not going to loop after the transformation. So it would be nice to fix it on that side, too. The patch avoids about half of profile mismatches caused by cunroll. Pass dump id and name |static mismatcdynamic mismatch |in count |in count 107t cunrolli | 3 +3| 17251 +17251 115t threadfull | 3 | 14376 -2875 116t vrp | 5 +2| 30908 +16532 117t dse | 5 | 30908 118t dce | 3 -2| 17251 -13657 127t ch | 13 +10| 17251 131t dom | 39 +26| 17251 133t isolate-paths | 47 +8| 17251 134t reassoc | 49 +2| 17251 136t forwprop | 53 +4| 202501 +185250 159t cddce | 61 +8| 216211 +13710 161t ldist | 62 +1| 216211 172t ifcvt | 66 +4| 373711 +157500 173t vect | 143 +77| 9802097 +9428386 176t cunroll | 221 +78| 15639591 +5837494 183t loopdone | 218 -3| 15577640 -61951 195t fre | 214 -4| 15577640 197t dom | 213 -1| 16671606 +1093966 199t threadfull | 215 +2| 16879581 +207975 200t vrp | 217 +2| 17077750 +198169 204t dce | 215 -2| 17004486 -73264 206t sink | 213 -2| 17004486 211t cddce | 219 +6| 17005926 +1440 255t optimized | 217 -2| 17005926 256r expand | 210 -7| 19571573 +2565647 258r into_cfglayout | 208 -2| 19571573 275r loop2_unroll | 212 +4| 22992432 +3420859 291r ce2 | 210 -2| 23011838 312r pro_and_epilogue | 230 +20| 23073776 +61938 315r jump2 | 236 +6| 27110534 +4036758 323r bbro | 229 -7| 21826835 -5283699 W/o the patch cunroll does: 176t cunroll | 294 +151|126548439 +116746342 and we end up with 291 mismatches at bbro. Bootstrapped/regtested x86_64-linux. Plan to commit it after the scale_loop_frequency patch. gcc/ChangeLog: PR middle-end/25623 * tree-ssa-loop-ch.cc (ch_base::copy_headers): Scale loop frequency to maximal number of iterations determined. * tree-ssa-loop-ivcanon.cc (try_unroll_loop_completely): Likewise. gcc/testsuite/ChangeLog: PR middle-end/25623 * gfortran.dg/pr25623-2.f90: New test.