[gcc r17-3279] match: Try to remove casts for `(int)-(unsigned)a`[PR107765]

https://gcc.gnu.org/g:8d004ef91c4f7c315519975ffaec78d28d4a21ff

commit r17-3279-g8d004ef91c4f7c315519975ffaec78d28d4a21ff
Author: Andrea Pinski <[email protected]>
Date:   Mon Jul 27 23:02:07 2026 -0700

    match: Try to remove casts for `(int)-(unsigned)a`[PR107765]
    
    This adds some extra checks to see if we can remove the casts
    for signed integer overflow reasons while doing a negative.
    This is needed more due to the recent patch which adds them
    in some cases.
    
    This also changes TYPE_UNSIGNED to be TYPE_OVERFLOW_WRAPS to
    allow this to happen with -fwrapv too.
    
    Changes since v1:
    * Use expr_not_equal_to and simplify the if stmt.
    Also use TYPE_OVERFLOW_WRAPS instead of TYPE_UNSIGNED.
    
    Bootstrapped and tested on x86_64-linux-gnu.
    
            PR tree-optimization/107765
    
    gcc/ChangeLog:
    
            * match.pd (`(cast)-(cast)a`): Expand to
            use expr_not_equal_to of INT_MIN.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/tree-ssa/neg-cast-1.c: New test.
            * gcc.dg/tree-ssa/neg-cast-4.c: New test.
    
    Signed-off-by: Andrea Pinski <[email protected]>

Diff:
---
 gcc/match.pd                               | 10 +++++++---
 gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c | 23 +++++++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c | 16 ++++++++++++++++
 3 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/gcc/match.pd b/gcc/match.pd
index f43d2e79363b..4ddddc43bd72 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1231,13 +1231,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    show up.  Else it is safe if the negation is done in an unsigned type.
    Note the outer cast cannot be a boolean type as the only valid values
    are 0,-1/1 (depending on the signedness of the boolean) and the negative
-   is there to get the correct value.  */
+   is there to get the correct value.
+   Also handle the case where we know that we won't cause a signed
+   integer overflow at the point of the negation.  */
 (simplify
- (convert (negate:s@1 (convert:s @0)))
+ (convert (negate:s@1 (convert:s@ic @0)))
  (if (INTEGRAL_TYPE_P (type)
       && tree_nop_conversion_p (type, TREE_TYPE (@1))
       && (TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
-	  || TYPE_UNSIGNED (type))
+	  || TYPE_OVERFLOW_WRAPS (type)
+	  || expr_not_equal_to (@ic, wi::min_value (signed_type_for (type)),
+				gimple_match_ctx (@1)))
       && TREE_CODE (type) != BOOLEAN_TYPE)
     (negate (convert @0))))
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c
new file mode 100644
index 000000000000..ec5d0e15251b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -fdump-tree-cddce1" } */
+/* PR tree-optimization/107765 */
+
+int a(int input)
+{
+    if (input == -__INT_MAX__-1) return 1;
+    unsigned t = input;
+    int tt =  -t;
+    return tt == -input;
+}
+
+int b(int input)
+{
+    if (input == -__INT_MAX__-1) __builtin_trap();
+    unsigned t = input;
+    int tt =  -t;
+    return tt;
+}
+
+/* { dg-final { scan-tree-dump "return 1" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "\\(unsigned int\\)" "cddce1" } } */
+/* { dg-final { scan-tree-dump-not "\\(int\\)" "cddce1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c
new file mode 100644
index 000000000000..fe3fe6a2eccf
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-phiopt2-details -fdump-tree-optimized" } */
+/* PR tree-optimization/107765 */
+
+int b(int input)
+{
+    if (input == -__INT_MAX__-1) return input;
+    unsigned t = input;
+    int tt =  -t;
+    return tt;
+}
+
+/* { dg-final { scan-tree-dump-not "if " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\(unsigned int\\)" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\(int\\)" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "converted to straightline code" 1 "phiopt2" } } */