| Message ID | 20151119145703.GH21807@redhat.com |
|---|---|
| State | New |
| Headers | show |
On November 19, 2015 3:57:03 PM GMT+01:00, Marek Polacek <polacek@redhat.com> wrote: >This fixes a failure to optimize division by an unsigned. The comment >before >the condition I'm fixing says "When vr0.max < 0, vr1.min != 0 and ..." >but >"&& !compare_values (vr1.min, zero)" actually ensures that vr1.min is >zero. >(Indeed, the following int_const_binop would attemp to divide by zero >and >return NULL_TREE.) > >With this, (a / x) gets a correct range [-2, 0] and we're able to >optimize >the condition away, thus even the abort () call. (This won't work on >targets >where long long == int.) > >Bootstrapped/regtested on x86_64-linux, ok for trunk? OK. Richard. >2015-11-19 Marek Polacek <polacek@redhat.com> > > PR tree-optimization/68431 > * tree-vrp.c (extract_range_from_binary_expr_1): Fix condition. > > * gcc.dg/tree-ssa/pr68431.c: New test. > >diff --git gcc/testsuite/gcc.dg/tree-ssa/pr68431.c >gcc/testsuite/gcc.dg/tree-ssa/pr68431.c >index e69de29..3bd3843 100644 >--- gcc/testsuite/gcc.dg/tree-ssa/pr68431.c >+++ gcc/testsuite/gcc.dg/tree-ssa/pr68431.c >@@ -0,0 +1,16 @@ >+/* PR tree-optimization/68431 */ >+/* { dg-options "-O2 -fdump-tree-vrp1-details" } */ >+ >+unsigned int x = 1; >+int >+main (void) >+{ >+ long long int a = -2LL; >+ int t = 1 <= (a / x); >+ if (t != 0) >+ __builtin_abort (); >+ >+ return 0; >+} >+ >+/* { dg-final { scan-tree-dump-times "Folding predicate .*to 0" 1 >"vrp1" } } */ >diff --git gcc/tree-vrp.c gcc/tree-vrp.c >index e67048e..736082b 100644 >--- gcc/tree-vrp.c >+++ gcc/tree-vrp.c >@@ -2975,7 +2975,7 @@ extract_range_from_binary_expr_1 (value_range >*vr, > if (vr1.type == VR_RANGE > && !symbolic_range_p (&vr0) > && !symbolic_range_p (&vr1) >- && !compare_values (vr1.min, zero)) >+ && compare_values (vr1.min, zero) != 0) > max = int_const_binop (code, vr0.max, vr1.min); > else > max = zero; > > Marek
diff --git gcc/testsuite/gcc.dg/tree-ssa/pr68431.c gcc/testsuite/gcc.dg/tree-ssa/pr68431.c index e69de29..3bd3843 100644 --- gcc/testsuite/gcc.dg/tree-ssa/pr68431.c +++ gcc/testsuite/gcc.dg/tree-ssa/pr68431.c @@ -0,0 +1,16 @@ +/* PR tree-optimization/68431 */ +/* { dg-options "-O2 -fdump-tree-vrp1-details" } */ + +unsigned int x = 1; +int +main (void) +{ + long long int a = -2LL; + int t = 1 <= (a / x); + if (t != 0) + __builtin_abort (); + + return 0; +} + +/* { dg-final { scan-tree-dump-times "Folding predicate .*to 0" 1 "vrp1" } } */ diff --git gcc/tree-vrp.c gcc/tree-vrp.c index e67048e..736082b 100644 --- gcc/tree-vrp.c +++ gcc/tree-vrp.c @@ -2975,7 +2975,7 @@ extract_range_from_binary_expr_1 (value_range *vr, if (vr1.type == VR_RANGE && !symbolic_range_p (&vr0) && !symbolic_range_p (&vr1) - && !compare_values (vr1.min, zero)) + && compare_values (vr1.min, zero) != 0) max = int_const_binop (code, vr0.max, vr1.min); else max = zero;