GCC - revision history

Dank: /* Useful flags */ mention 10.1's -fanalyzer

2020-07-30T03:49:11Z

Useful flags: mention 10.1's -fanalyzer

← Older revision		Revision as of 03:49, 30 July 2020
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	* <tt>-fmax-errors=n</tt> print a maximum of n errors, 0 (the default) being unbounded		* <tt>-fmax-errors=n</tt> print a maximum of n errors, 0 (the default) being unbounded
	* <tt>-E</tt> to generate preprocessor output, <tt>-s</tt> to generate assembly output		* <tt>-E</tt> to generate preprocessor output, <tt>-s</tt> to generate assembly output
			* <tt>-fanalyzer</tt> (since 10.1) to do rich static analysis [https://clearlinux.org/blogs-news/major-improvements-gcc-101 ClearLinux blog]

	==Optimization==		==Optimization==

Dank at 05:02, 8 November 2019

2019-11-08T05:02:33Z

← Older revision		Revision as of 05:02, 8 November 2019
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			==Useful flags==
			* <tt>-fmax-errors=n</tt> print a maximum of n errors, 0 (the default) being unbounded
			* <tt>-E</tt> to generate preprocessor output, <tt>-s</tt> to generate assembly output

	==Optimization==		==Optimization==
	* Use '''-Q -Ox --help=optimizers''' to determine which optimization flags are enabled for a given -Ox setting (or read the info pages).		* Use '''-Q -Ox --help=optimizers''' to determine which optimization flags are enabled for a given -Ox setting (or read the info pages).
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	* [http://gcc.gnu.org/onlinedocs/gccint/ GNU Compiler Collection Internals]		* [http://gcc.gnu.org/onlinedocs/gccint/ GNU Compiler Collection Internals]
	* [[Core]] files		* [[Core]] files
			* [[Questions]]

Dank at 12:33, 29 December 2011

2011-12-29T12:33:38Z

← Older revision		Revision as of 12:33, 29 December 2011
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			==Optimization==
			* Use '''-Q -Ox --help=optimizers''' to determine which optimization flags are enabled for a given -Ox setting (or read the info pages).
			* [[Compiler Design\|Dataflow analysis]] is only performed at -O2 or above, and thus at least this level of optimization is necessary for use-of-uninitialized-variable warnings and such.
	==Extensions to [[C]]==		==Extensions to [[C]]==
	Extensions to the [[C]] language are documented at the [http://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html#C-Extensions online gcc docs], and in the Info pages distributed with gcc.		Extensions to the [[C]] language are documented at the [http://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html#C-Extensions online gcc docs], and in the Info pages distributed with gcc.

Dank: /* See also */

2010-04-05T09:48:19Z

Dank: /* Inline Assembly */

2010-03-21T00:10:51Z

Inline Assembly

← Older revision		Revision as of 00:10, 21 March 2010
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	* outputs, inputs and clobbers are expressed in a colon-delimited list of comma-delimited lists of the form [''asmsymbol''] "''constraints''" (''c symbol'')		* outputs, inputs and clobbers are expressed in a colon-delimited list of comma-delimited lists of the form [''asmsymbol''] "''constraints''" (''c symbol'')
	** operand constraints are properties of the assembly code, not the values		** operand constraints are properties of the assembly code, not the values
			** without "=" or "+" constraint modifier, operands are assumed to be read-only
	** compiler verifies that all outputs are lvalues. types of operands are '''not''' checked.		** compiler verifies that all outputs are lvalues. types of operands are '''not''' checked.
	** "cc" logical register ought be listed as a clobber if the conditional code register is changed		** "cc" logical register ought be listed as a clobber if the conditional code register is changed
			** "memory" must be listed as clobbered if memory is touched in an unpredictable fashion
			* constraint modifiers:
			** "=": operand is write-only (previous value needn't be preserved until write)
			** "+": operand is read-write (can't be arbitrarily used)
			** "&": operand is clobbered early (prior to use of all inputs), and thus can't be placed atop an input operand's

	==Intermediate Representations==		==Intermediate Representations==

Dank: /* Inline Assembly */

2010-03-21T00:04:14Z

Inline Assembly

← Older revision		Revision as of 00:04, 21 March 2010
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	** operand constraints are properties of the assembly code, not the values		** operand constraints are properties of the assembly code, not the values
	** compiler verifies that all outputs are lvalues. types of operands are '''not''' checked.		** compiler verifies that all outputs are lvalues. types of operands are '''not''' checked.
			** "cc" logical register ought be listed as a clobber if the conditional code register is changed

	==Intermediate Representations==		==Intermediate Representations==

Dank: /* Inline Assembly */

2010-03-21T00:01:32Z

Inline Assembly

← Older revision		Revision as of 00:01, 21 March 2010
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	* outputs, inputs and clobbers are expressed in a colon-delimited list of comma-delimited lists of the form [''asmsymbol''] "''constraints''" (''c symbol'')		* outputs, inputs and clobbers are expressed in a colon-delimited list of comma-delimited lists of the form [''asmsymbol''] "''constraints''" (''c symbol'')
	** operand constraints are properties of the assembly code, not the values		** operand constraints are properties of the assembly code, not the values
			** compiler verifies that all outputs are lvalues. types of operands are '''not''' checked.

	==Intermediate Representations==		==Intermediate Representations==

Dank: /* Inline Assembly */

2010-03-21T00:00:14Z

Inline Assembly

← Older revision		Revision as of 00:00, 21 March 2010
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	* The [http://sourceware.org/binutils/docs/as/index.html GNU assembler] (gas) is used for assembly and syntax.		* The [http://sourceware.org/binutils/docs/as/index.html GNU assembler] (gas) is used for assembly and syntax.
	* Statements can be arbitrarily reordered by default, or anchored with the <tt>volatile</tt> qualifier		* Statements can be arbitrarily reordered by default, or anchored with the <tt>volatile</tt> qualifier
			* outputs, inputs and clobbers are expressed in a colon-delimited list of comma-delimited lists of the form [''asmsymbol''] "''constraints''" (''c symbol'')
			** operand constraints are properties of the assembly code, not the values

	==Intermediate Representations==		==Intermediate Representations==

Dank: /* Inline Assembly */

2010-03-20T23:55:08Z

Inline Assembly

← Older revision		Revision as of 23:55, 20 March 2010
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	* Functions only referenced by inline assembly might not have code generated for them; use of the <tt>used</tt> [[GCC#Function_Attributes\|function attribute]] will force generation.		* Functions only referenced by inline assembly might not have code generated for them; use of the <tt>used</tt> [[GCC#Function_Attributes\|function attribute]] will force generation.
	* The [http://sourceware.org/binutils/docs/as/index.html GNU assembler] (gas) is used for assembly and syntax.		* The [http://sourceware.org/binutils/docs/as/index.html GNU assembler] (gas) is used for assembly and syntax.
			* Statements can be arbitrarily reordered by default, or anchored with the <tt>volatile</tt> qualifier

	==Intermediate Representations==		==Intermediate Representations==

Dank: /* Function Attributes */

2009-10-04T08:04:26Z

Function Attributes

← Older revision		Revision as of 08:04, 4 October 2009
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	* <tt>aligned</tt> - takes a single parameter, the minimum number of bytes at which to align the function. <tt>-falign-functions</tt> will override this, if larger.		* <tt>aligned</tt> - takes a single parameter, the minimum number of bytes at which to align the function. <tt>-falign-functions</tt> will override this, if larger.
	* <tt>malloc</tt> - indicates that any value returned does not [[Compiler Design\|alias]] any other currently-valid pointers		* <tt>malloc</tt> - indicates that any value returned does not [[Compiler Design\|alias]] any other currently-valid pointers
	* <tt>alloc_size</tt> - takes one or two parameters and indicates that the function will return a pointer to an allocated chunk of memory having either the size provided by a single argument, or the product of two arguments. This is necessary for ~~the~~ <tt>__builtin_object_size</tt>'s correct functioning.		* <tt>alloc_size</tt> - takes one or two parameters and indicates that the function will return a pointer to an allocated chunk of memory having either the size provided by a single argument, or the product of two arguments. This is necessary for <tt>__builtin_object_size</tt>'s correct functioning.
	* <tt>pure</tt> (2.96) - indicates that the function has no side-effects save its return value, which is based only on calls to other <tt>pure</tt> functions, the function's own parameters and/or non-volatile global memory.		* <tt>pure</tt> (2.96) - indicates that the function has no side-effects save its return value, which is based only on calls to other <tt>pure</tt> functions, the function's own parameters and/or non-volatile global memory.
	* <tt>const</tt> (2.5) - stronger than <tt>pure</tt>, a <tt>pure</tt> function which does not dereference any pointer parameters, use global memory or call non-<tt>const</tt> functions.		* <tt>const</tt> (2.5) - stronger than <tt>pure</tt>, a <tt>pure</tt> function which does not dereference any pointer parameters, use global memory or call non-<tt>const</tt> functions.

← Older revision		Revision as of 09:48, 5 April 2010
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	* "[http://www.cs.lth.se/home/Jonas_Skeppstedt/kongstad.pdf An Implementation of Global Value Numbering in the GNU Compiler Collection, with Performance Measurements]" (Kongstad 2004)		* "[http://www.cs.lth.se/home/Jonas_Skeppstedt/kongstad.pdf An Implementation of Global Value Numbering in the GNU Compiler Collection, with Performance Measurements]" (Kongstad 2004)
	* [http://gcc.gnu.org/onlinedocs/gccint/ GNU Compiler Collection Internals]		* [http://gcc.gnu.org/onlinedocs/gccint/ GNU Compiler Collection Internals]
			* [[Core]] files