diff options
Diffstat (limited to 'toolchain/gcc/3.4.2/400-mips-pr17565.patch')
-rw-r--r-- | toolchain/gcc/3.4.2/400-mips-pr17565.patch | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/toolchain/gcc/3.4.2/400-mips-pr17565.patch b/toolchain/gcc/3.4.2/400-mips-pr17565.patch new file mode 100644 index 0000000000..7ae6aa56f6 --- /dev/null +++ b/toolchain/gcc/3.4.2/400-mips-pr17565.patch @@ -0,0 +1,102 @@ +[committed] Fix target/17565: asms in delay slots + + * From: Richard Sandiford <rsandifo at redhat dot com> + * To: gcc-patches at gcc dot gnu dot org + * Date: Mon, 20 Sep 2004 07:55:58 +0100 + * Subject: [committed] Fix target/17565: asms in delay slots + +The MIPS port was allowing asms to be put into delay slots if the +compiler guesses they are only one instruction long. This is wrong +because of the possibility of it containing macros. + +The problem can be reproduced as an assembler warning +in the following testcase: + +int foo (int n) +{ + register int k asm ("$16") = n; + if (k > 0) + { + bar (); + asm ("li %0,0x12345678" : "=r" (k)); + } + return k; +} + +because the multi-instruction asm statement goes into the delay +slot of the call to bar(). + +This is reduced from a much more serious linux problem. Linux is fond +of using empty asm statements, and since gcc estimates empty asms to be +one instruction long, they too might be put into delay slots. This +actually has the effect of putting the following instruction into the +delay slot instead. Since there's no assembler warning, the problem was +only detected as a run-time failure. + +The fix is simple: set the asm value of "can_delay" to "no". +Tested on mipsisa64-elf, applied to mainline. + +This problem goes back to at least 2.95, so it isn't technically a +regression. On the other hand, it's the kind of bug that could trigger +for different types of code in different releases, so I'm sure there's +a testcase that fails (say) in 3.4 and not in 2.95. Will probably ask +Mark for permission to backport to 3.4. + +Richard + + + PR target/17565 + * config/mips/mips.md (define_asm_attributes): Set can_delay to no. + +testsuite/ + * gcc.target/mips/asm-1.c: New test. + +Index: config/mips/mips.md +=================================================================== +RCS file: /cvs/gcc/gcc/gcc/config/mips/mips.md,v +retrieving revision 1.306 +diff -c -p -F^\([(a-zA-Z0-9_]\|#define\) -r1.306 mips.md +*** gcc/gcc/config/mips/mips.md 13 Sep 2004 19:32:05 -0000 1.306 +--- gcc/gcc/config/mips/mips.md 20 Sep 2004 06:52:31 -0000 +*************** (define_attr "may_clobber_hilo" "no,yes" +*** 266,272 **** + + ;; Describe a user's asm statement. + (define_asm_attributes +! [(set_attr "type" "multi")]) + + ;; ......................... + ;; +--- 266,273 ---- + + ;; Describe a user's asm statement. + (define_asm_attributes +! [(set_attr "type" "multi") +! (set_attr "can_delay" "no")]) + + ;; ......................... + ;; +Index: testsuite/gcc.target/mips/asm-1.c +=================================================================== +RCS file: testsuite/gcc.target/mips/asm-1.c +diff -N testsuite/gcc.target/mips/asm-1.c +*** gcc/gcc/testsuite/gcc.target/mips/asm-1.c 1 Jan 1970 00:00:00 -0000 +--- gcc/gcc/testsuite/gcc.target/mips/asm-1.c 20 Sep 2004 06:52:31 -0000 +*************** +*** 0 **** +--- 1,14 ---- ++ /* PR target/17565. GCC used to put the asm into the delay slot ++ of the call. */ ++ /* { dg-do assemble } */ ++ /* { dg-options "-O" } */ ++ int foo (int n) ++ { ++ register int k asm ("$16") = n; ++ if (k > 0) ++ { ++ bar (); ++ asm ("li %0,0x12345678" : "=r" (k)); ++ } ++ return k; ++ } + |