[PATCH 2/5][Arm] New pattern for CSINV instructions

This patch adds a new pattern, *thumb2_csinv, for generating CSINV nstructions.

This pattern relies on a few general changes that will be used throughout
the following patches:
	- A new macro, TARGET_COND_ARITH, which is only true on 8.1-M Mainline
	  and represents the existence of these conditional instructions.
	- A change to the cond exec hook, arm_have_conditional_execution, which
	  now returns false if TARGET_COND_ARITH before reload. This allows for
	  some ifcvt transformations when they would usually be disabled. I've
	  written a rather verbose comment (with the risk of over-explaining)
	  as it's a bit of a confusing change.
	- One new predicate.
	- *thumb2_movcond has been restricted to only match if !TARGET_COND_ARITH,
	  otherwise it triggers undesirable combines.

gcc/ChangeLog:

	* config/arm/arm.h (TARGET_COND_ARITH): New macro.
	* config/arm/arm.c (arm_have_conditional_execution): Return false if
	TARGET_COND_ARITH before reload.
	* config/arm/predicates.md (arm_comparison_operation): Returns true if
	comparing CC_REGNUM with constant zero.
	* config/arm/thumb2.md (*thumb2_csinv): New.
	(*thumb2_movcond): Don't match if TARGET_COND_ARITH.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/csinv-1.c: New test.

Co-authored-by: Omar Tahir <omar.tahir@arm.com>

5 files changed, 68 insertions, 4 deletions

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 932f907..022ef6c 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -29866,12 +29866,23 @@ arm_frame_pointer_required (void)
   return false;
 }
 
-/* Only thumb1 can't support conditional execution, so return true if
-   the target is not thumb1.  */
+/* Implement the TARGET_HAVE_CONDITIONAL_EXECUTION hook.
+   All modes except THUMB1 have conditional execution.
+   If we have conditional arithmetic, return false before reload to
+   enable some ifcvt transformations. */
 static bool
 arm_have_conditional_execution (void)
 {
-  return !TARGET_THUMB1;
+  bool has_cond_exec, enable_ifcvt_trans;
+
+  /* Only THUMB1 cannot support conditional execution. */
+  has_cond_exec = !TARGET_THUMB1;
+
+  /* Enable ifcvt transformations if we have conditional arithmetic, but only
+     before reload. */
+  enable_ifcvt_trans = TARGET_COND_ARITH && !reload_completed;
+
+  return has_cond_exec && !enable_ifcvt_trans;
 }
 
 /* The AAPCS sets the maximum alignment of a vector to 64 bits.  */
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 3887c51..f4d3676 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -177,6 +177,10 @@ emission of floating point pcs attributes.  */
 
 #define TARGET_CRC32			(arm_arch_crc)
 
+/* Thumb-2 but also has some conditional arithmetic instructions like csinc,
+   csinv, etc. */
+#define TARGET_COND_ARITH		(arm_arch8_1m_main)
+
 /* The following two macros concern the ability to execute coprocessor
    instructions for VFPv3 or NEON.  TARGET_VFP3/TARGET_VFPD32 are currently
    only ever tested when we know we are generating for VFP hardware; we need
diff --git a/gcc/config/arm/predicates.md b/gcc/config/arm/predicates.md
index 981eec5..2144520 100644
--- a/gcc/config/arm/predicates.md
+++ b/gcc/config/arm/predicates.md
@@ -485,6 +485,18 @@
   (and (match_operand 0 "expandable_comparison_operator")
        (match_test "maybe_get_arm_condition_code (op) != ARM_NV")))
 
+(define_special_predicate "arm_comparison_operation"
+  (match_code "eq,ne,le,lt,ge,gt,geu,gtu,leu,ltu,unordered,
+         ordered,unlt,unle,unge,ungt")
+{
+  if (XEXP (op, 1) != const0_rtx)
+    return false;
+  rtx op0 = XEXP (op, 0);
+  if (!REG_P (op0) || REGNO (op0) != CC_REGNUM)
+    return false;
+  return maybe_get_arm_condition_code (op) != ARM_NV;
+})
+
 (define_special_predicate "lt_ge_comparison_operator"
   (match_code "lt,ge"))
 
diff --git a/gcc/config/arm/thumb2.md b/gcc/config/arm/thumb2.md
index 1a5f24e..d648ba1 100644
--- a/gcc/config/arm/thumb2.md
+++ b/gcc/config/arm/thumb2.md
@@ -938,6 +938,20 @@
    (set_attr "type" "multiple")]
 )
 
+(define_insn "*thumb2_csinv"
+  [(set (match_operand:SI 0 "arm_general_register_operand" "=r, r")
+        (if_then_else:SI
+         (match_operand 1 "arm_comparison_operation" "")
+         (not:SI (match_operand:SI 2 "arm_general_register_operand" "r, r"))
+         (match_operand:SI 3 "reg_or_zero_operand" "r, Pz")))]
+  "TARGET_COND_ARITH"
+  "@
+   csinv\\t%0, %3, %2, %D1
+   csinv\\t%0, zr, %2, %D1"
+  [(set_attr "type" "csel")
+   (set_attr "predicable" "no")]
+)
+
 (define_insn "*thumb2_movcond"
   [(set (match_operand:SI 0 "s_register_operand" "=Ts,Ts,Ts")
 	(if_then_else:SI
@@ -947,7 +961,7 @@
 	 (match_operand:SI 1 "arm_rhs_operand" "0,TsI,?TsI")
 	 (match_operand:SI 2 "arm_rhs_operand" "TsI,0,TsI")))
    (clobber (reg:CC CC_REGNUM))]
-  "TARGET_THUMB2"
+  "TARGET_THUMB2 && !TARGET_COND_ARITH"
   "*
   if (GET_CODE (operands[5]) == LT
       && (operands[4] == const0_rtx))
diff --git a/gcc/testsuite/gcc.target/arm/csinv-1.c b/gcc/testsuite/gcc.target/arm/csinv-1.c
new file mode 100644
index 0000000..6b5383a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/csinv-1.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_arch_v8_1m_main_ok } */
+/* { dg-options "-O2 -march=armv8.1-m.main" } */
+
+int
+test_csinv32_condasn1(int w0, int w1, int w2, int w3)
+{
+  int w4;
+
+  /* { dg-final { scan-assembler "csinv\tr\[0-9\]*.*ne" } } */
+  w4 = (w0 == w1) ? ~w2 : w3;
+  return w4;
+}
+
+int
+test_csinv32_condasn2(int w0, int w1, int w2, int w3)
+{
+  int w4;
+
+  /* { dg-final { scan-assembler "csinv\tr\[0-9\]*.*eq" } } */
+  w4 = (w0 == w1) ? w3 : ~w2;
+  return w4;
+}