MATCH: first of the value replacement moving from phiopt

This moves a few simple patterns that are done in value replacement
in phiopt over to match.pd. Just the simple ones which might show up
in other code.

This allows some optimizations to happen even without depending
on sinking from happening and in some cases where phiopt is not
invoked (cond-1.c is an example there).

Changes since v1:
* v2: Add an extra testcase to showcase improvements at -O1.

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

gcc/ChangeLog:

	* match.pd: (`a == 0 ? b : b + a`,
	`a == 0 ? b : b - a`): New patterns.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/cond-1.c: New test.
	* gcc.dg/tree-ssa/phi-opt-value-1.c: New test.
	* gcc.dg/tree-ssa/phi-opt-value-1a.c: New test.
	* gcc.dg/tree-ssa/phi-opt-value-2.c: New test.

5 files changed, 86 insertions, 0 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 7d651a6..22899c5 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4145,6 +4145,20 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        && (INTEGRAL_TYPE_P (TREE_TYPE (@0))))
        (op (mult (convert:type @0) @2) @1))))
 
+/* ?: Value replacement. */
+/* a == 0 ? b : b + a  -> b + a */
+(for op (plus bit_ior bit_xor)
+ (simplify
+  (cond (eq @0 integer_zerop) @1 (op:c@2 @1 @0))
+   @2))
+/* a == 0 ? b : b - a  -> b - a */
+/* a == 0 ? b : b ptr+ a  -> b ptr+ a */
+/* a == 0 ? b : b shift/rotate a -> b shift/rotate a */
+(for op (lrotate rrotate lshift rshift minus pointer_plus)
+ (simplify
+  (cond (eq @0 integer_zerop) @1 (op@2 @1 @0))
+   @2))
+
 /* Simplifications of shift and rotates.  */
 
 (for rotate (lrotate rrotate)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cond-1.c b/gcc/testsuite/gcc.dg/tree-ssa/cond-1.c
new file mode 100644
index 0000000..478a818
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cond-1.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized-raw" } */
+
+int sub(int a, int b, int c, int d) {
+  int e = (a == 0);
+  int f = !e;
+  c = b;
+  d = b - a ;
+  return ((-e & c) | (-f & d));
+}
+
+/* In the end we end up with `(a == 0) ? (b - a) : b`
+   which then can be optimized to just `(b - a)`. */
+
+/* { dg-final { scan-tree-dump-not "cond_expr," "optimized" } } */
+/* { dg-final { scan-tree-dump-not "eq_expr," "optimized" } } */
+/* { dg-final { scan-tree-dump-times "minus_expr," 1 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1.c
new file mode 100644
index 0000000..a90de89
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* Phi-OPT should be able to optimize this without sinking being invoked. */
+/* { dg-options "-O -fdump-tree-phiopt2 -fdump-tree-optimized -fno-tree-sink" } */
+
+char *f(char *a, __SIZE_TYPE__ b) {
+  char *d = a + b;
+  if (b == 0) return a;
+  return d;
+}
+int sub(int a, int b, int c) {
+  int d = a - b;
+  if (b == 0) return a;
+  return d;
+}
+
+/* { dg-final { scan-tree-dump-not "goto" "phiopt2" } } */
+/* { dg-final { scan-tree-dump-not "goto" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1a.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1a.c
new file mode 100644
index 0000000..b884f94
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-1a.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+[[gnu::const]]
+int constcall(int);
+
+int f(int a, int b)
+{
+  int c = b+a;
+  int t = constcall(c);
+  int d;
+  if (a == 0) d= b; else d= c;
+  return constcall(d) + t;
+}
+
+/* There should be no if statement and 2 calls to call1. */
+/* { dg-final { scan-tree-dump-not "if " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "constcall " 1 "optimized" } } */
+
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-2.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-2.c
new file mode 100644
index 0000000..809ccfe
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-value-2.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* Phi-OPT should be able to optimize this without sinking being invoked. */
+/* { dg-options "-O -fdump-tree-phiopt2 -fdump-tree-optimized -fno-tree-sink" } */
+
+int f(int a, int b, int c) {
+  int d = a + b;
+  if (c > 5) return c;
+  if (a == 0) return b;
+  return d;
+}
+
+unsigned rot(unsigned x, int n) {
+  const int bits = __CHAR_BIT__ * __SIZEOF_INT__;
+  int t = ((x << n) | (x >> (bits - n)));
+  return (n == 0) ? x : t;
+}
+
+/* { dg-final { scan-tree-dump-times "goto" 2 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times "goto" 2 "optimized" } } */