MATCH: Support `(a != (CST+1)) & (a > CST)` optimizations

Even though this is done via reassocation, match can support
these with a simple change to detect that the difference is just
one. This allows to optimize these earlier and even during phiopt
for an example.

This patch adds the following cases:
(a != (CST+1)) & (a > CST) -> a > (CST+1)
(a != (CST-1)) & (a < CST) -> a < (CST-1)
(a == (CST-1)) | (a >= CST) -> a >= (CST-1)
(a == (CST+1)) | (a <= CST) -> a <= (CST+1)

Canonicalizations of comparisons causes this case to show up more.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/106164

gcc/ChangeLog:

	* match.pd (`(X CMP1 CST1) AND/IOR (X CMP2 CST2)`):
	Expand to support constants that are off by one.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr21643.c: Update test now that match does
	the combing of the comparisons.
	* gcc.dg/tree-ssa/cmpbit-5.c: New test.
	* gcc.dg/tree-ssa/phi-opt-35.c: New test.

4 files changed, 111 insertions, 3 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 7ecf556..07ffd83 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2970,10 +2970,20 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	    && operand_equal_p (@1, @2)))
     (with
      {
+      bool one_before = false;
+      bool one_after = false;
       int cmp = 0;
       if (TREE_CODE (@1) == INTEGER_CST
 	  && TREE_CODE (@2) == INTEGER_CST)
-	cmp = tree_int_cst_compare (@1, @2);
+	{
+	  cmp = tree_int_cst_compare (@1, @2);
+	  if (cmp < 0
+	      && wi::to_wide (@1) == wi::to_wide (@2) - 1)
+	    one_before = true;
+	  if (cmp > 0
+	      && wi::to_wide (@1) == wi::to_wide (@2) + 1)
+	    one_after = true;
+	}
       bool val;
       switch (code2)
 	 {
@@ -2998,6 +3008,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
            && code2 == LE_EXPR
 	   && cmp == 0)
        (lt @0 @1))
+      /* (a != (b+1)) & (a > b) -> a > (b+1) */
+      (if (code1 == NE_EXPR
+           && code2 == GT_EXPR
+	   && one_after)
+       (gt @0 @1))
+      /* (a != (b-1)) & (a < b) -> a < (b-1) */
+      (if (code1 == NE_EXPR
+           && code2 == LT_EXPR
+	   && one_before)
+       (lt @0 @1))
      )
     )
    )
@@ -3069,10 +3089,20 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	    && operand_equal_p (@1, @2)))
     (with
      {
+      bool one_before = false;
+      bool one_after = false;
       int cmp = 0;
       if (TREE_CODE (@1) == INTEGER_CST
 	  && TREE_CODE (@2) == INTEGER_CST)
-	cmp = tree_int_cst_compare (@1, @2);
+	{
+	  cmp = tree_int_cst_compare (@1, @2);
+	  if (cmp < 0
+	      && wi::to_wide (@1) == wi::to_wide (@2) - 1)
+	    one_before = true;
+	  if (cmp > 0
+	      && wi::to_wide (@1) == wi::to_wide (@2) + 1)
+	    one_after = true;
+	}
       bool val;
       switch (code2)
 	{
@@ -3097,6 +3127,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
            && code2 == LT_EXPR
 	   && cmp == 0)
        (le @0 @1))
+      /* (a == (b-1)) | (a >= b) -> a >= (b-1) */
+      (if (code1 == EQ_EXPR
+           && code2 == GE_EXPR
+	   && one_before)
+       (ge @0 @1))
+      /* (a == (b+1)) | (a <= b) -> a <= (b-1) */
+      (if (code1 == EQ_EXPR
+           && code2 == LE_EXPR
+	   && one_after)
+       (le @0 @1))
      )
     )
    )
diff --git a/gcc/testsuite/gcc.dg/pr21643.c b/gcc/testsuite/gcc.dg/pr21643.c
index 4e7f93d..42517b5 100644
--- a/gcc/testsuite/gcc.dg/pr21643.c
+++ b/gcc/testsuite/gcc.dg/pr21643.c
@@ -86,4 +86,8 @@ f9 (unsigned char c)
   return 1;
 }
 
-/* { dg-final { scan-tree-dump-times "Optimizing range tests c_\[0-9\]*.D. -.0, 31. and -.32, 32.\[\n\r\]* into" 6 "reassoc1" } }  */
+/* Note with match being able to simplify this, optimizing range tests is no longer needed here. */
+/* Equivalence: _7 | _2 -> c_5(D) <= 32 */
+/* old test: dg-final  scan-tree-dump-times "Optimizing range tests c_\[0-9\]*.D. -.0, 31. and -.32, 32.\[\n\r\]* into" 6 "reassoc1"   */
+/* { dg-final { scan-tree-dump-times "Equivalence: _\[0-9\]+ \\\| _\[0-9\]+ -> c_\[0-9\]+.D. <= 32" 5 "reassoc1" } }  */
+/* { dg-final { scan-tree-dump-times "Equivalence: _\[0-9\]+ \& _\[0-9\]+ -> c_\[0-9\]+.D. > 32" 1 "reassoc1" } }  */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-5.c b/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-5.c
new file mode 100644
index 0000000..d81a129
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-5.c
@@ -0,0 +1,51 @@
+/* PR tree-optimization/106164 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-forwprop1-details" } */
+
+
+int f(int a)
+{
+  int c = a != 2;
+  int d = a >= 2;
+  return c & d;
+}
+int g(int b)
+{
+  int c = b != -1;
+  int d = b <= -1;
+  return c & d;
+}
+
+
+int g_(int e)
+{
+  int c = e != -2;
+  int d = e <= -2;
+  return c & d;
+}
+
+int f1(int x)
+{
+  int c = x == 2;
+  int d = x <= 1;
+  return c | d;
+}
+int g1(int y)
+{
+  int c = y == -1;
+  int d = y > -1;
+  return c | d;
+}
+int g1_(int z)
+{
+  int c = z == -2;
+  int d = z >= -1;
+  return c | d;
+}
+
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = a_\[0-9\]+.D. > 2" "forwprop1" } }  */
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = b_\[0-9\]+.D. < -1" "forwprop1" } }  */
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = e_\[0-9\]+.D. < -2" "forwprop1" } }  */
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = x_\[0-9\]+.D. <= 2" "forwprop1" } }  */
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = y_\[0-9\]+.D. >= -1" "forwprop1" } }  */
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]+ = z_\[0-9\]+.D. >= -2" "forwprop1" } }  */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-35.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-35.c
new file mode 100644
index 0000000..c52c64c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-35.c
@@ -0,0 +1,13 @@
+/* PR tree-optimization/106164 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-phiopt2" } */
+
+_Bool f2(int a)
+{
+  if (a != 2)
+    return a > 1;
+  return 0;
+}
+/* phiopt2 should be able to optimize this to `a > 2` via match and simplify */
+/* { dg-final { scan-tree-dump "_\[0-9\]+ = a_\[0-9\]+.D. > 2" "phiopt2" } }  */
+/* { dg-final { scan-tree-dump-not "a_\[0-9\]+.D. != 2" "phiopt2" } }  */