| Message ID | 20140404161818.GA26795@bart |
|---|---|
| State | New |
| Headers | show |
On 04/04/14 10:18, Andreas Krebbel wrote: > Hi, > > the attached patch modifies the builtin-bswap-6/7 testcases in order > to prevent GCC from using math instead of a compare. Only with a > compare the folding in combine actually takes place. > > Whether the return value is produce with a compare or not depends > again on the value of branch cost. > > Ideally we would be able to do the folding also with the math trick > but it is probably not that easy since we have already lost the > information that in the end all we need is a 0 or a 1. > > Ok? > > Bye, > > -Andreas- > > 2014-04-04 Andreas Krebbel <Andreas.Krebbel@de.ibm.com> > > * gcc.dg/builtin-bswap-6.c: Adjust return value to disable GCC > optimization. > * gcc.dg/builtin-bswap-7.c: Likewise. OK. Jeff
On Fri, Apr 4, 2014 at 7:51 PM, Jeff Law <law@redhat.com> wrote: > On 04/04/14 10:18, Andreas Krebbel wrote: >> >> Hi, >> >> the attached patch modifies the builtin-bswap-6/7 testcases in order >> to prevent GCC from using math instead of a compare. Only with a >> compare the folding in combine actually takes place. >> >> Whether the return value is produce with a compare or not depends >> again on the value of branch cost. >> >> Ideally we would be able to do the folding also with the math trick >> but it is probably not that easy since we have already lost the >> information that in the end all we need is a 0 or a 1. >> >> Ok? >> >> Bye, >> >> -Andreas- >> >> 2014-04-04 Andreas Krebbel <Andreas.Krebbel@de.ibm.com> >> >> * gcc.dg/builtin-bswap-6.c: Adjust return value to disable GCC >> optimization. >> * gcc.dg/builtin-bswap-7.c: Likewise. > > OK. The adjusted testcases now fail on x86_64/i?86 at least. See PR60776. Richard. > Jeff >
diff --git a/gcc/testsuite/gcc.dg/builtin-bswap-6.c b/gcc/testsuite/gcc.dg/builtin-bswap-6.c index 024ebf1..6f0c782 100644 --- a/gcc/testsuite/gcc.dg/builtin-bswap-6.c +++ b/gcc/testsuite/gcc.dg/builtin-bswap-6.c @@ -3,6 +3,10 @@ /* { dg-options "-O -fdump-rtl-combine" } */ /* { dg-options "-O -fdump-rtl-combine -march=z900" { target s390-*-* } } */ +/* The test intentionally returns 1/2 instead of the obvious 0/1 to + prevent GCC from calculating the return value with arithmetic + instead of a comparison. */ + #include <stdint.h> #define BS(X) __builtin_bswap32(X) @@ -11,28 +15,28 @@ int foo1 (uint32_t a) { if (BS (a) == 0xA0000) return 1; - return 0; + return 2; } int foo2 (uint32_t a) { if (BS (a) != 0xA0000) return 1; - return 0; + return 2; } int foo3 (uint32_t a, uint32_t b) { if (BS (a) == BS (b)) return 1; - return 0; + return 2; } int foo4 (uint32_t a, uint32_t b) { if (BS (a) != BS (b)) return 1; - return 0; + return 2; } /* { dg-final { scan-rtl-dump-not "bswapsi" "combine" } } */ diff --git a/gcc/testsuite/gcc.dg/builtin-bswap-7.c b/gcc/testsuite/gcc.dg/builtin-bswap-7.c index 399b825..0eecdd8 100644 --- a/gcc/testsuite/gcc.dg/builtin-bswap-7.c +++ b/gcc/testsuite/gcc.dg/builtin-bswap-7.c @@ -3,6 +3,10 @@ /* { dg-require-effective-target lp64 } */ /* { dg-options "-O -fdump-rtl-combine" } */ +/* The test intentionally returns 1/2 instead of the obvious 0/1 to + prevent GCC from calculating the return value with arithmetic + instead of a comparison. */ + #include <stdint.h> #define BS(X) __builtin_bswap64(X) @@ -11,28 +15,28 @@ int foo1 (uint64_t a) { if (BS (a) == 0xA00000000) return 1; - return 0; + return 2; } int foo2 (uint64_t a) { if (BS (a) != 0xA00000000) return 1; - return 0; + return 2; } int foo3 (uint64_t a, uint64_t b) { if (BS (a) == BS (b)) return 1; - return 0; + return 2; } int foo4 (uint64_t a, uint64_t b) { if (BS (a) != BS (b)) return 1; - return 0; + return 2; } /* { dg-final { scan-rtl-dump-not "bswapdi" "combine" } } */