asm inline

The Linux kernel people want a feature that makes GCC pretend some
inline assembler code is tiny (while it would think it is huge), so
that such code will be inlined essentially always instead of
essentially never.

This patch lets you say "asm inline" instead of just "asm", with the
result that that inline assembler is always counted as minimum cost
for inlining.  It implements this for C and C++, making "inline"
another asm-qualifier (supplementing "volatile" and "goto").


	* doc/extend.texi (Using Assembly Language with C): Document asm inline.
	(Size of an asm): Fix typo.  Document asm inline.
	* gimple-pretty-print.c (dump_gimple_asm): Handle asm inline.
	* gimple.h (enum gf_mask): Add GF_ASM_INLINE.
	(gimple_asm_set_volatile): Fix typo.
	(gimple_asm_inline_p): New.
	(gimple_asm_set_inline): New.
	* gimplify.c (gimplify_asm_expr): Propagate the asm inline flag from
	tree to gimple.
	* ipa-icf-gimple.c (func_checker::compare_gimple_asm): Compare the
	gimple_asm_inline_p flag, too.
	* tree-core.h (tree_base): Document that protected_flag is ASM_INLINE_P
	in an ASM_EXPR.
	* tree-inline.c (estimate_num_insns): If gimple_asm_inline_p return
	a minimum size for an asm.
	* tree.h (ASM_INLINE_P): New.

gcc/c/
	* c-parser.c (c_parser_asm_statement): Detect the inline keyword
	after asm.  Pass a flag for it to build_asm_expr.
	* c-tree.h (build_asm_expr): Update declaration.
	* c-typeck.c (build_asm_stmt): Add is_inline parameter.  Use it to
	set ASM_INLINE_P.

gcc/cp/
	* cp-tree.h (finish_asm_stmt): Update declaration.
	* parser.c (cp_parser_asm_definition): Detect the inline keyword
	after asm.  Pass a flag for it to finish_asm_stmt.
	* pt.c (tsubst_expr): Pass the ASM_INLINE_P flag to finish_asm_stmt.
	* semantics.c (finish_asm_stmt): Add inline_p parameter.  Use it to
	set ASM_INLINE_P.

gcc/testsuite/
	* c-c++-common/torture/asm-inline.c: New testcase.
	* gcc.dg/asm-qual-2.c: Test asm inline, too.

From-SVN: r266860

1 files changed, 14 insertions, 1 deletions

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 70c46cf..7700ab9 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -8460,6 +8460,10 @@ various @option{-std} options, use @code{__asm__} instead of
 @item volatile
 The optional @code{volatile} qualifier has no effect. 
 All basic @code{asm} blocks are implicitly volatile.
+
+@item inline
+If you use the @code{inline} qualifier, then for inlining purposes the size
+of the asm is taken as the smallest size possible (@pxref{Size of an asm}).
 @end table
 
 @subsubheading Parameters
@@ -8603,6 +8607,10 @@ values to produce output values. However, your @code{asm} statements may
 also produce side effects. If so, you may need to use the @code{volatile} 
 qualifier to disable certain optimizations. @xref{Volatile}.
 
+@item inline
+If you use the @code{inline} qualifier, then for inlining purposes the size
+of the asm is taken as the smallest size possible (@pxref{Size of an asm}).
+
 @item goto
 This qualifier informs the compiler that the @code{asm} statement may 
 perform a jump to one of the labels listed in the @var{GotoLabels}.
@@ -10061,7 +10069,7 @@ does this by counting the number of instructions in the pattern of the
 @code{asm} and multiplying that by the length of the longest
 instruction supported by that processor.  (When working out the number
 of instructions, it assumes that any occurrence of a newline or of
-whatever statement separator character is supported by the assembler --
+whatever statement separator character is supported by the assembler ---
 typically @samp{;} --- indicates the end of an instruction.)
 
 Normally, GCC's estimate is adequate to ensure that correct
@@ -10072,6 +10080,11 @@ space in the object file than is needed for a single instruction.
 If this happens then the assembler may produce a diagnostic saying that
 a label is unreachable.
 
+@cindex @code{asm inline}
+This size is also used for inlining decisions.  If you use @code{asm inline}
+instead of just @code{asm}, then for inlining purposes the size of the asm
+is taken as the minimum size, ignoring how many instructions GCC thinks it is.
+
 @node Alternate Keywords
 @section Alternate Keywords
 @cindex alternate keywords