AArch64: Enable TARGET_CONST_ANCHOR

Enable TARGET_CONST_ANCHOR to allow complex constants to be created via
immediate add/sub.  Use a 24-bit range as that enables a 3 or 4-instruction
immediate to be replaced by 2 add/sub instructions.  Fix the costing of
add/sub to support 24-bit and 12-bit shifted immediates.
The generated code for the testcase is now the same or better than LLVM.
It also results in a small codesize reduction on SPEC.

gcc/
	* config/aarch64/aarch64.cc (aarch64_rtx_costs): Add correct costs
	for 24-bit and 12-bit shifted immediate add/sub.
	(TARGET_CONST_ANCHOR): Define.
	* config/aarch64/predicates.md (aarch64_pluslong_immediate):
	Fix range check.

gcc/testsuite/
	* gcc.target/aarch64/movk_3.c: New test.

3 files changed, 70 insertions, 1 deletions

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 523d49a..73515c1 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -14237,6 +14237,16 @@ cost_plus:
 	    return true;
 	  }
 
+	if (aarch64_pluslong_immediate (op1, mode))
+	  {
+	    /* 24-bit add in 2 instructions or 12-bit shifted add.  */
+	    if ((INTVAL (op1) & 0xfff) != 0)
+	      *cost += COSTS_N_INSNS (1);
+
+	    *cost += rtx_cost (op0, mode, PLUS, 0, speed);
+	    return true;
+	  }
+
 	*cost += rtx_cost (op1, mode, PLUS, 1, speed);
 
 	/* Look for ADD (extended register).  */
@@ -28091,6 +28101,9 @@ aarch64_libgcc_floating_mode_supported_p
 #undef TARGET_HAVE_SHADOW_CALL_STACK
 #define TARGET_HAVE_SHADOW_CALL_STACK true
 
+#undef TARGET_CONST_ANCHOR
+#define TARGET_CONST_ANCHOR 0x1000000
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-aarch64.h"
diff --git a/gcc/config/aarch64/predicates.md b/gcc/config/aarch64/predicates.md
index 6175875..ff7f73d 100644
--- a/gcc/config/aarch64/predicates.md
+++ b/gcc/config/aarch64/predicates.md
@@ -146,7 +146,7 @@
 
 (define_predicate "aarch64_pluslong_immediate"
   (and (match_code "const_int")
-       (match_test "(INTVAL (op) < 0xffffff && INTVAL (op) > -0xffffff)")))
+       (match_test "IN_RANGE (INTVAL (op), -0xffffff, 0xffffff)")))
 
 (define_predicate "aarch64_sminmax_immediate"
   (and (match_code "const_int")
diff --git a/gcc/testsuite/gcc.target/aarch64/movk_3.c b/gcc/testsuite/gcc.target/aarch64/movk_3.c
new file mode 100644
index 0000000..9e8c0c4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/movk_3.c
@@ -0,0 +1,56 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 --save-temps" } */
+
+
+/* 2 MOV */
+void f16 (long *p)
+{
+  p[0] = 0x1234;
+  p[2] = 0x1235;
+}
+
+/* MOV, MOVK and ADD */
+void f32_1 (long *p)
+{
+  p[0] = 0x12345678;
+  p[2] = 0x12345678 + 0xfff;
+}
+
+/* 2 MOV, 2 MOVK */
+void f32_2 (long *p)
+{
+  p[0] = 0x12345678;
+  p[2] = 0x12345678 + 0x555555;
+}
+
+/* MOV, MOVK and ADD */
+void f32_3 (long *p)
+{
+  p[0] = 0x12345678;
+  p[2] = 0x12345678 + 0x999000;
+}
+
+/* MOV, 2 MOVK and ADD */
+void f48_1 (long *p)
+{
+  p[0] = 0x123456789abc;
+  p[2] = 0x123456789abc + 0xfff;
+}
+
+/* MOV, 2 MOVK and 2 ADD */
+void f48_2 (long *p)
+{
+  p[0] = 0x123456789abc;
+  p[2] = 0x123456789abc + 0x666666;
+}
+
+/* 2 MOV, 4 MOVK */
+void f48_3 (long *p)
+{
+  p[0] = 0x123456789abc;
+  p[2] = 0x123456789abc + 0x1666666;
+}
+
+/* { dg-final { scan-assembler-times "mov\tx\[0-9\]+, \[0-9\]+" 10 } } */
+/* { dg-final { scan-assembler-times "movk\tx\[0-9\]+, 0x\[0-9a-f\]+" 12 } } */
+/* { dg-final { scan-assembler-times "add\tx\[0-9\]+, x\[0-9\]+, \[0-9\]+" 5 } } */