x86: Replace ne:CCC/ne:CCO with UNSPEC_CC_NE in neg patterns

In i386.md, neg patterns which set MODE_CC register like

(set (reg:CCC FLAGS_REG)
     (ne:CCC (match_operand:SWI48 1 "general_reg_operand") (const_int 0)))

can lead to errors when operand 1 is a constant value.  If FLAGS_REG in

(set (reg:CCC FLAGS_REG)
     (ne:CCC (const_int 2) (const_int 0)))

is set to 1, RTX simplifiers may simplify

(set (reg:SI 93)
     (neg:SI (ltu:SI (reg:CCC 17 flags) (const_int 0 [0]))))

as

(set (reg:SI 93)
     (neg:SI (ltu:SI (const_int 1) (const_int 0 [0]))))

which leads to incorrect results since LTU on MODE_CC register isn't the
same as "unsigned less than" in x86 backend.  To prevent RTL optimizers
from setting MODE_CC register to a constant, use UNSPEC_CC_NE to replace
ne:CCC/ne:CCO when setting FLAGS_REG in neg patterns.

gcc/

	PR target/107172
	* config/i386/i386.md (UNSPEC_CC_NE): New.
	Replace ne:CCC/ne:CCO with UNSPEC_CC_NE in neg patterns.

gcc/testsuite/

	PR target/107172
	* gcc.target/i386/pr107172.c: New test.

2 files changed, 51 insertions, 20 deletions

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index baf1f1f..aaa678e 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -113,6 +113,7 @@
   UNSPEC_PEEPSIB
   UNSPEC_INSN_FALSE_DEP
   UNSPEC_SBB
+  UNSPEC_CC_NE
 
   ;; For SSE/MMX support:
   UNSPEC_FIX_NOTRUNC
@@ -11470,7 +11471,7 @@
   "&& reload_completed"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_dup 1) (const_int 0)))
+	  (unspec:CCC [(match_dup 1) (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 0) (neg:DWIH (match_dup 1)))])
    (parallel
     [(set (match_dup 2)
@@ -11499,7 +11500,8 @@
 	(match_operand:SWI48 1 "nonimmediate_gr_operand"))
    (parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_operand:SWI48 2 "general_reg_operand") (const_int 0)))
+	  (unspec:CCC [(match_operand:SWI48 2 "general_reg_operand")
+		       (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 2) (neg:SWI48 (match_dup 2)))])
    (parallel
     [(set (match_dup 0)
@@ -11517,7 +11519,7 @@
    && !reg_mentioned_p (operands[2], operands[1])"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_dup 2) (const_int 0)))
+	  (unspec:CCC [(match_dup 2) (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 2) (neg:SWI48 (match_dup 2)))])
    (parallel
     [(set (match_dup 0)
@@ -11543,7 +11545,8 @@
      (clobber (reg:CC FLAGS_REG))])
    (parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_operand:SWI48 1 "general_reg_operand") (const_int 0)))
+	  (unspec:CCC [(match_operand:SWI48 1 "general_reg_operand")
+		       (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 1) (neg:SWI48 (match_dup 1)))])
    (parallel
     [(set (match_dup 0)
@@ -11559,7 +11562,7 @@
   "REGNO (operands[0]) != REGNO (operands[1])"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_dup 1) (const_int 0)))
+	  (unspec:CCC [(match_dup 1) (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 1) (neg:SWI48 (match_dup 1)))])
    (parallel
     [(set (match_dup 0)
@@ -11635,9 +11638,9 @@
 
 (define_insn "*neg<mode>_ccc_1"
   [(set (reg:CCC FLAGS_REG)
-	(ne:CCC
-	  (match_operand:SWI 1 "nonimmediate_operand" "0")
-	  (const_int 0)))
+	(unspec:CCC
+	  [(match_operand:SWI 1 "nonimmediate_operand" "0")
+	   (const_int 0)] UNSPEC_CC_NE))
    (set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m")
 	(neg:SWI (match_dup 1)))]
   ""
@@ -11647,9 +11650,9 @@
 
 (define_insn "*neg<mode>_ccc_2"
   [(set (reg:CCC FLAGS_REG)
-	(ne:CCC
-	  (match_operand:SWI 1 "nonimmediate_operand" "0")
-	  (const_int 0)))
+	(unspec:CCC
+	  [(match_operand:SWI 1 "nonimmediate_operand" "0")
+	   (const_int 0)] UNSPEC_CC_NE))
    (clobber (match_scratch:SWI 0 "=<r>"))]
   ""
   "neg{<imodesuffix>}\t%0"
@@ -11659,8 +11662,8 @@
 (define_expand "x86_neg<mode>_ccc"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_operand:SWI48 1 "register_operand")
-		  (const_int 0)))
+	  (unspec:CCC [(match_operand:SWI48 1 "register_operand")
+		       (const_int 0)] UNSPEC_CC_NE))
      (set (match_operand:SWI48 0 "register_operand")
 	  (neg:SWI48 (match_dup 1)))])])
 
@@ -11686,8 +11689,9 @@
 ;; Negate with jump on overflow.
 (define_expand "negv<mode>3"
   [(parallel [(set (reg:CCO FLAGS_REG)
-		   (ne:CCO (match_operand:SWI 1 "register_operand")
-			   (match_dup 3)))
+		   (unspec:CCO
+		     [(match_operand:SWI 1 "register_operand")
+		      (match_dup 3)] UNSPEC_CC_NE))
 	      (set (match_operand:SWI 0 "register_operand")
 		   (neg:SWI (match_dup 1)))])
    (set (pc) (if_then_else
@@ -11703,8 +11707,9 @@
 
 (define_insn "*negv<mode>3"
   [(set (reg:CCO FLAGS_REG)
-	(ne:CCO (match_operand:SWI 1 "nonimmediate_operand" "0")
-		(match_operand:SWI 2 "const_int_operand")))
+	(unspec:CCO [(match_operand:SWI 1 "nonimmediate_operand" "0")
+		     (match_operand:SWI 2 "const_int_operand")]
+		    UNSPEC_CC_NE))
    (set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m")
 	(neg:SWI (match_dup 1)))]
   "ix86_unary_operator_ok (NEG, <MODE>mode, operands)
@@ -11770,7 +11775,7 @@
    "&& 1"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_dup 1) (const_int 0)))
+	  (unspec:CCC [(match_dup 1) (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 2) (neg:DWIH (match_dup 1)))])
    (parallel
     [(set (match_dup 5)
@@ -11814,7 +11819,7 @@
    "&& 1"
   [(parallel
     [(set (reg:CCC FLAGS_REG)
-	  (ne:CCC (match_dup 1) (const_int 0)))
+	  (unspec:CCC [(match_dup 1) (const_int 0)] UNSPEC_CC_NE))
      (set (match_dup 2) (neg:DWIH (match_dup 1)))])
    (parallel
     [(set (match_dup 5)
@@ -21456,7 +21461,7 @@
 	    (const_int 0))))]
   ""
   [(set (reg:CCC FLAGS_REG)
-	(ne:CCC (match_dup 1) (const_int 0)))
+	(unspec:CCC [(match_dup 1) (const_int 0)] UNSPEC_CC_NE))
    (set (match_dup 0)
 	(neg:SWI (ltu:SWI (reg:CCC FLAGS_REG) (const_int 0))))])
 
diff --git a/gcc/testsuite/gcc.target/i386/pr107172.c b/gcc/testsuite/gcc.target/i386/pr107172.c
new file mode 100644
index 0000000..d2c85f3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr107172.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+/* { dg-options "-O1 -ftree-vrp" } */
+
+int a, c, d;
+int
+main()
+{
+  long e = 1;
+  int f = a = 1;
+L1:
+  if (a)
+    a = 2;
+  int h = e = ~e;
+  c = -1;
+  if (e >= a)
+    goto L2;
+  if (-1 > a)
+    goto L1;
+  if (a)
+    f = -1;
+L2:
+  d = (-f + d) & h;
+  if (d)
+    __builtin_abort();
+  return 0;
+}