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* [gcc r13-3217] [PR107195] Set range to zero when nonzero mask is 0.
@ 2022-10-11 8:31 Aldy Hernandez
0 siblings, 0 replies; only message in thread
From: Aldy Hernandez @ 2022-10-11 8:31 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:c4d15dddf6b9eacb36f535807ad2ee364af46e04
commit r13-3217-gc4d15dddf6b9eacb36f535807ad2ee364af46e04
Author: Aldy Hernandez <aldyh@redhat.com>
Date: Mon Oct 10 20:42:10 2022 +0200
[PR107195] Set range to zero when nonzero mask is 0.
When solving 0 = _15 & 1, we calculate _15 as:
[irange] int [-INF, -2][0, +INF] NONZERO 0xfffffffe
The known value of _15 is [0, 1] NONZERO 0x1 which is intersected with
the above, yielding:
[0, 1] NONZERO 0x0
This eventually gets copied to a _Bool [0, 1] NONZERO 0x0.
This is problematic because here we have a bool which is zero, but
returns false for irange::zero_p, since the latter does not look at
nonzero bits. This causes logical_combine to assume the range is
not-zero, and all hell breaks loose.
I think we should just normalize a nonzero mask of 0 to [0, 0] at
creation, thus avoiding all this.
PR tree-optimization/107195
gcc/ChangeLog:
* value-range.cc (irange::set_range_from_nonzero_bits): Set range
to [0,0] when nonzero mask is 0.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/pr107195-1.c: New test.
* gcc.dg/tree-ssa/pr107195-2.c: New test.
Diff:
---
gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c | 15 +++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c | 16 ++++++++++++++++
gcc/value-range.cc | 5 +++++
3 files changed, 36 insertions(+)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c
new file mode 100644
index 00000000000..a0c20dbd4b1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c
@@ -0,0 +1,15 @@
+// { dg-do run }
+// { dg-options "-O1 -fno-tree-ccp" }
+
+int a, b;
+int main() {
+ int c = 0;
+ if (a)
+ c = 1;
+ c = 1 & (a && c) && b;
+ if (a) {
+ b = c;
+ __builtin_abort ();
+ }
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c
new file mode 100644
index 00000000000..d447c78bdd3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c
@@ -0,0 +1,16 @@
+// { dg-do run }
+// { dg-options "-O1" }
+
+int a, b;
+int main() {
+ int c = 0;
+ long d;
+ for (; b < 1; b++) {
+ (c && d) & 3 || a;
+ d = c;
+ c = -1;
+ if (d)
+ __builtin_abort();
+ }
+ return 0;
+}
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index a14f9bc4394..e07d2aa9a5b 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -2903,6 +2903,11 @@ irange::set_range_from_nonzero_bits ()
}
return true;
}
+ else if (popcount == 0)
+ {
+ set_zero (type ());
+ return true;
+ }
return false;
}
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