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Subject: [gentoo-commits] proj/gcc-patches:master commit in: 15.0.0/gentoo/
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X-VCS-Files: 15.0.0/gentoo/82_all_PR118409-ifcombine.patch 15.0.0/gentoo/README.history
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Date: Mon, 13 Jan 2025 03:20:29 +0000 (UTC)
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commit: 9990b777a4ae73b77ef376ee7aebfd0ac8523754
Author: Sam James <sam <AT> gentoo <DOT> org>
AuthorDate: Mon Jan 13 03:20:09 2025 +0000
Commit: Sam James <sam <AT> gentoo <DOT> org>
CommitDate: Mon Jan 13 03:20:09 2025 +0000
URL: https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=9990b777
15.0.0: add ifcombine patch
Bug: https://gcc.gnu.org/PR118409
Signed-off-by: Sam James <sam <AT> gentoo.org>
15.0.0/gentoo/82_all_PR118409-ifcombine.patch | 146 ++++++++++++++++++++++++++
15.0.0/gentoo/README.history | 4 +
2 files changed, 150 insertions(+)
diff --git a/15.0.0/gentoo/82_all_PR118409-ifcombine.patch b/15.0.0/gentoo/82_all_PR118409-ifcombine.patch
new file mode 100644
index 0000000..e599f21
--- /dev/null
+++ b/15.0.0/gentoo/82_all_PR118409-ifcombine.patch
@@ -0,0 +1,146 @@
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118409#c26
+
+[ifcombine] propagate signbit mask to XOR right-hand operand
+
+From: Alexandre Oliva <oliva@adacore.com>
+
+If a single-bit bitfield takes up the sign bit of a storage unit,
+comparing the corresponding bitfield between two objects loads the
+storage units, XORs them, converts the result to signed char, and
+compares it with zero: ((signed char)(a.<byte> ^ c.<byte>) >= 0).
+
+fold_truth_andor_for_ifcombine recognizes the compare with zero as a
+sign bit test, then it decomposes the XOR into an equality test.
+
+The problem is that, after this decomposition, that figures out the
+width of the accessed fields, we apply the sign bit mask to the
+left-hand operand of the compare, but we failed to also apply it to
+the right-hand operand when both were taken from the same XOR.
+
+This patch fixes that.
+
+
+for gcc/ChangeLog
+
+ PR tree-optimization/118409
+ * gimple-fold.cc (fold_truth_andor_for_ifcombine): Apply the
+ signbit mask to the right-hand XOR operand too.
+
+for gcc/testsuite/ChangeLog
+
+ PR tree-optimization/118409
+ * gcc.dg/field-merge-20.c: New.
+---
+ gcc/gimple-fold.cc | 20 ++++++++++
+ gcc/testsuite/gcc.dg/field-merge-20.c | 64 +++++++++++++++++++++++++++++++++
+ 2 files changed, 84 insertions(+)
+ create mode 100644 gcc/testsuite/gcc.dg/field-merge-20.c
+
+diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
+index a3987c4590ae6..93ed8b3abb056 100644
+--- a/gcc/gimple-fold.cc
++++ b/gcc/gimple-fold.cc
+@@ -8270,6 +8270,16 @@ fold_truth_andor_for_ifcombine (enum tree_code code, tree truth_type,
+ ll_and_mask = sign;
+ else
+ ll_and_mask &= sign;
++ if (l_xor)
++ {
++ if (!lr_and_mask.get_precision ())
++ lr_and_mask = sign;
++ else
++ lr_and_mask &= sign;
++ if (l_const.get_precision ())
++ l_const &= wide_int::from (lr_and_mask,
++ l_const.get_precision (), UNSIGNED);
++ }
+ }
+
+ if (rsignbit)
+@@ -8279,6 +8289,16 @@ fold_truth_andor_for_ifcombine (enum tree_code code, tree truth_type,
+ rl_and_mask = sign;
+ else
+ rl_and_mask &= sign;
++ if (r_xor)
++ {
++ if (!rr_and_mask.get_precision ())
++ rr_and_mask = sign;
++ else
++ rr_and_mask &= sign;
++ if (r_const.get_precision ())
++ r_const &= wide_int::from (rr_and_mask,
++ r_const.get_precision (), UNSIGNED);
++ }
+ }
+
+ /* If either comparison code is not correct for our logical operation,
+diff --git a/gcc/testsuite/gcc.dg/field-merge-20.c b/gcc/testsuite/gcc.dg/field-merge-20.c
+new file mode 100644
+index 0000000000000..44ac7fae50dc5
+--- /dev/null
++++ b/gcc/testsuite/gcc.dg/field-merge-20.c
+@@ -0,0 +1,64 @@
++/* { dg-do run } */
++/* { dg-options "-O1" } */
++
++/* tree-optimization/118409 */
++
++/* Check that tests involving a sign bit of a storage unit are handled
++ correctly. The compares are turned into xor tests by earlier passes, and
++ ifcombine has to propagate the sign bit mask to the right hand of the
++ compare extracted from the xor, otherwise we'll retain unwanted bits for the
++ compare. */
++
++typedef struct {
++ int p : __CHAR_BIT__;
++ int d : 1;
++ int b : __CHAR_BIT__ - 2;
++ int e : 1;
++} g;
++
++g a = {.d = 1, .e = 1}, c = {.b = 1, .d = 1, .e = 1};
++
++__attribute__((noipa))
++int f1 ()
++{
++ if (a.d == c.d
++ && a.e == c.e)
++ return 0;
++ return -1;
++}
++
++__attribute__((noipa))
++int f2 ()
++{
++ if (a.d != c.d
++ || a.e != c.e)
++ return -1;
++ return 0;
++}
++
++__attribute__((noipa))
++int f3 ()
++{
++ if (c.d == a.d
++ && c.e == a.e)
++ return 0;
++ return -1;
++}
++
++__attribute__((noipa))
++int f4 ()
++{
++ if (c.d != a.d
++ || c.e != a.e)
++ return -1;
++ return 0;
++}
++
++int main() {
++ if (f1 () < 0
++ || f2 () < 0
++ || f3 () < 0
++ || f4 () < 0)
++ __builtin_abort();
++ return 0;
++}
diff --git a/15.0.0/gentoo/README.history b/15.0.0/gentoo/README.history
index f3ab09a..1f53f35 100644
--- a/15.0.0/gentoo/README.history
+++ b/15.0.0/gentoo/README.history
@@ -1,3 +1,7 @@
+38 ????
+
+ + 82_all_PR118409-ifcombine.patch
+
37 13 January 2025
- 77_all_PR118112-c-c-UX-improvements-to-too-few-many-arguments-errors.patch