inline-asm: Add - constraint modifier support for toplevel extended asm [PR41045]

The following patch adds - constraint modifier support (only in toplevel asms),
which one can use to allow i, s and n constraint to accept SYMBOL_REFs
even with -fpic.
So, the recommended way mark toplevel asm as defining some symbol
would be ":" constraint (usually with cc modifier in the pattern), while
to mark toplevel asm as using some symbol (again, either function or
variable), one would use "-s" constraint again with address of that function
or variable.

2024-12-18  Jakub Jelinek  <jakub@redhat.com>

	PR c/41045
gcc/
	* stmt.cc (parse_output_constraint, parse_input_constraint): Handle
	- modifier.
	* recog.h (raw_constraint_p): Declare.
	* recog.cc (raw_constraint_p): New variable.
	(asm_operand_ok, constrain_operands): Handle - modifier.
	* common.md (i, s, n): For raw_constraint_p don't require
	LEGITIMATE_PIC_OPERAND_P.
	* doc/md.texi: Document - constraint modifier.
gcc/c/
	* c-typeck.cc (build_asm_expr): Reject - constraint modifier inside
	of a function.
gcc/cp/
	* semantics.cc (finish_asm_stmt): Reject - constraint modifier inside
	of a function.
gcc/testsuite/
	* c-c++-common/toplevel-asm-4.c: Add missing %cc2 use in template, add
	bar, x, &y operands with "-i" and "-s" constraints.
	(x, y): New variables.
	(bar): Declare.
	* c-c++-common/toplevel-asm-7.c: New test.
	* c-c++-common/toplevel-asm-8.c: New test.

10 files changed, 100 insertions, 7 deletions

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 7be645f..9756eda 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -12332,6 +12332,11 @@ build_asm_expr (location_t loc, tree string, tree outputs, tree inputs,
 		}
 	    }
 	}
+      else if (output != error_mark_node && strstr (constraint, "-"))
+	{
+	  error_at (loc, "%<-%> modifier used inside of a function");
+	  output = error_mark_node;
+	}
 
       TREE_VALUE (tail) = output;
     }
@@ -12417,6 +12422,11 @@ build_asm_expr (location_t loc, tree string, tree outputs, tree inputs,
 		}
 	    }
 	}
+      else if (input != error_mark_node && strstr (constraint, "-"))
+	{
+	  error_at (loc, "%<-%> modifier used inside of a function");
+	  input = error_mark_node;
+	}
 
       TREE_VALUE (tail) = input;
     }
diff --git a/gcc/common.md b/gcc/common.md
index 6a2d453..3cefa93 100644
--- a/gcc/common.md
+++ b/gcc/common.md
@@ -92,13 +92,13 @@
 (define_constraint "i"
   "Matches a general integer constant."
   (and (match_test "CONSTANT_P (op)")
-       (match_test "!flag_pic || LEGITIMATE_PIC_OPERAND_P (op)")))
+       (match_test "!flag_pic || raw_constraint_p || LEGITIMATE_PIC_OPERAND_P (op)")))
 
 (define_constraint "s"
   "Matches a symbolic integer constant."
   (and (match_test "CONSTANT_P (op)")
        (match_test "!CONST_SCALAR_INT_P (op)")
-       (match_test "!flag_pic || LEGITIMATE_PIC_OPERAND_P (op)")))
+       (match_test "!flag_pic || raw_constraint_p || LEGITIMATE_PIC_OPERAND_P (op)")))
 
 (define_constraint ":"
   "Defines a symbol."
@@ -108,7 +108,7 @@
 (define_constraint "n"
   "Matches a non-symbolic integer constant."
   (and (match_test "CONST_SCALAR_INT_P (op)")
-       (match_test "!flag_pic || LEGITIMATE_PIC_OPERAND_P (op)")))
+       (match_test "!flag_pic || raw_constraint_p || LEGITIMATE_PIC_OPERAND_P (op)")))
 
 (define_constraint "E"
   "Matches a floating-point constant."
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 948eb89..9912c5e 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2255,6 +2255,11 @@ finish_asm_stmt (location_t loc, int volatile_p, tree string,
 		    }
 		}
 	    }
+	  else if (operand != error_mark_node && strstr (constraint, "-"))
+	    {
+	      error_at (loc, "%<-%> modifier used inside of a function");
+	      operand = error_mark_node;
+	    }
 
 	  TREE_VALUE (t) = operand;
 	}
@@ -2383,6 +2388,11 @@ finish_asm_stmt (location_t loc, int volatile_p, tree string,
 		    }
 		}
 	    }
+	  else if (operand != error_mark_node && strstr (constraint, "-"))
+	    {
+	      error_at (loc, "%<-%> modifier used inside of a function");
+	      operand = error_mark_node;
+	    }
 
 	  TREE_VALUE (t) = operand;
 	}
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 0ed1bc1..0457bb5 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -1889,6 +1889,28 @@ register preferences.
   @dots{})
 @end smallexample
 @end ifset
+
+@cindex @samp{-} in constraint
+@item -
+Says that the selected following constraints within the same alternative
+should be matched differently.  Normally in PIC code symbolic operands
+in constraints like @samp{i}, @samp{s} or @samp{n} are not allowed at all
+or severely restricted.  The @samp{-} modifier, which is only allowed
+outside of functions, allows symbolic operands even in PIC code.  This
+modifier is usually used together with the @code{cc} operand modifier.
+
+@smallexample
+extern void foo (void), bar (void);
+int v;
+extern int w;
+asm (".globl %cc0, %cc2; .text; %cc0: call %cc1; ret; .data; %cc2: .word %cc3"
+     :: ":" (foo), "-s" (&bar), ":" (&w), "-i" (&v));
+@end smallexample
+
+This asm declaration tells the compiler it defines function @code{foo} and
+variable @code{w} and uses function @code{bar} and variable @code{v}.  This
+will compile even with PIC, but it is up to the user to ensure it will
+assemble correctly and have the expected behavior.
 @end table
 
 @node Machine Constraints
diff --git a/gcc/recog.cc b/gcc/recog.cc
index d1811f3..f4f1a6b 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -86,6 +86,9 @@ static operand_alternative asm_op_alt[MAX_RECOG_OPERANDS
 
 int which_alternative;
 
+/* True for inline asm operands with - constraint modifier.  */
+bool raw_constraint_p;
+
 /* Nonzero after end of reload pass.
    Set to 1 or 0 by toplev.cc.
    Controls the significance of (SUBREG (MEM)).  */
@@ -2287,6 +2290,7 @@ asm_operand_ok (rtx op, const char *constraint, const char **constraints)
       switch (c)
 	{
 	case ',':
+	  raw_constraint_p = false;
 	  constraint++;
 	  continue;
 
@@ -2337,6 +2341,11 @@ asm_operand_ok (rtx op, const char *constraint, const char **constraints)
 	    result = 1;
 	  break;
 
+	case '-':
+	  raw_constraint_p = true;
+	  constraint++;
+	  continue;
+
 	case '<':
 	case '>':
 	  /* ??? Before auto-inc-dec, auto inc/dec insns are not supposed
@@ -2394,8 +2403,12 @@ asm_operand_ok (rtx op, const char *constraint, const char **constraints)
 	constraint++;
       while (--len && *constraint && *constraint != ',');
       if (len)
-	return 0;
+	{
+	  raw_constraint_p = false;
+	  return 0;
+	}
     }
+  raw_constraint_p = false;
 
   /* For operands without < or > constraints reject side-effects.  */
   if (AUTO_INC_DEC && !incdec_ok && result && MEM_P (op))
@@ -3189,6 +3202,9 @@ constrain_operands (int strict, alternative_mask alternatives)
 	      case ',':
 		c = '\0';
 		break;
+	      case '-':
+		raw_constraint_p = true;
+		break;
 
 	      case '#':
 		/* Ignore rest of this alternative as far as
@@ -3344,6 +3360,7 @@ constrain_operands (int strict, alternative_mask alternatives)
 	      }
 	  while (p += len, c);
 
+	  raw_constraint_p = false;
 	  constraints[opno] = p;
 	  /* If this operand did not win somehow,
 	     this alternative loses.  */
diff --git a/gcc/recog.h b/gcc/recog.h
index 17ccdb6..b37af08 100644
--- a/gcc/recog.h
+++ b/gcc/recog.h
@@ -362,6 +362,9 @@ private:
    matched.  */
 extern int which_alternative;
 
+/* True for inline asm operands with - constraint modifier.  */
+extern bool raw_constraint_p;
+
 /* The following vectors hold the results from insn_extract.  */
 
 struct recog_data_d
diff --git a/gcc/stmt.cc b/gcc/stmt.cc
index 6789eee..8ee4333 100644
--- a/gcc/stmt.cc
+++ b/gcc/stmt.cc
@@ -268,7 +268,7 @@ parse_output_constraint (const char **constraint_p, int operand_num,
 	case 'E':  case 'F':  case 'G':  case 'H':
 	case 's':  case 'i':  case 'n':
 	case 'I':  case 'J':  case 'K':  case 'L':  case 'M':
-	case 'N':  case 'O':  case 'P':  case ',':
+	case 'N':  case 'O':  case 'P':  case ',':  case '-':
 	  break;
 
 	case '0':  case '1':  case '2':  case '3':  case '4':
@@ -363,7 +363,7 @@ parse_input_constraint (const char **constraint_p, int input_num,
       case 'E':  case 'F':  case 'G':  case 'H':
       case 's':  case 'i':  case 'n':
       case 'I':  case 'J':  case 'K':  case 'L':  case 'M':
-      case 'N':  case 'O':  case 'P':  case ',':
+      case 'N':  case 'O':  case 'P':  case ',':  case '-':
 	break;
 
       case ':':
diff --git a/gcc/testsuite/c-c++-common/toplevel-asm-4.c b/gcc/testsuite/c-c++-common/toplevel-asm-4.c
index 2f100a6..392eef5 100644
--- a/gcc/testsuite/c-c++-common/toplevel-asm-4.c
+++ b/gcc/testsuite/c-c++-common/toplevel-asm-4.c
@@ -3,6 +3,8 @@
 /* { dg-options "-O0" } */
 
 extern int v[42], w;
+int x[42], y;
 void foo (void);
+void bar (void) {}
 
-asm ("# %cc0: %cc1:" :: ":" (foo), ":" (v), ":" (&w));
+asm ("# %cc0: %cc1: %cc2: %cc3 %cc4 %cc5" :: ":" (foo), ":" (v), ":" (&w), "-i" (bar), "-s" (x), "-s" (&y));
diff --git a/gcc/testsuite/c-c++-common/toplevel-asm-7.c b/gcc/testsuite/c-c++-common/toplevel-asm-7.c
new file mode 100644
index 0000000..ed2603f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/toplevel-asm-7.c
@@ -0,0 +1,16 @@
+/* PR c/41045 */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+/* { dg-additional-options "-fpic" { target fpic } } */
+
+struct S { char a; long long b; int c; };
+enum E { E0, E1 = sizeof (struct S) + 15 };
+int v[42];
+void foo (void) {}
+
+asm ("# %0 %1 %2 %cc3 %cc4 %% %="
+     :: "i" (sizeof (struct S)),
+	"i" (__builtin_offsetof (struct S, c)),
+	"i" (E1),
+	"-s" (foo),
+	"-i" (v));
diff --git a/gcc/testsuite/c-c++-common/toplevel-asm-8.c b/gcc/testsuite/c-c++-common/toplevel-asm-8.c
new file mode 100644
index 0000000..3b8f471
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/toplevel-asm-8.c
@@ -0,0 +1,13 @@
+/* PR c/41045 */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+void
+foo (void)
+{
+  int m;
+  asm ("" : "=-m" (m));		/* { dg-error "'-' modifier used inside of a function" } */
+  asm ("" : : "-m" (m));	/* { dg-error "'-' modifier used inside of a function" } */
+  asm ("" : : "-i" (32));	/* { dg-error "'-' modifier used inside of a function" } */
+  asm ("" : : "-s" (foo));	/* { dg-error "'-' modifier used inside of a function" } */
+}