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Test case for PR rtl-optimization/60473

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PR rtl-optimization/60473 is code quality regression that has
been cured by improvements to register allocation.  For the function
in the test case, GCC 4.4, 4.5 and 4.6 generated very poor code
requiring two mov instructions, and GCC 4.7 and 4.8 (when the PR was
filed) produced better but still poor code with one mov instruction.
Since GCC 4.9 (including current mainline), it generates optimal
code with no mov instructions, matching what used to be generated
in GCC 4.1.

2020-08-04  Roger Sayle  <roger@nextmovesoftware.com>

gcc/testsuite/ChangeLog
	PR rtl-optimization/60473
	* gcc.target/i386/pr60473.c: New test.
This commit is contained in:
Roger Sayle 2020-08-04 16:56:06 +01:00
parent ca2b8c082c
commit 76eafcc395
1 changed files with 12 additions and 0 deletions
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gcc/testsuite/gcc.target/i386/pr60473.c Normal file
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/* PR rtl-optimization/60473 */
/* { dg-do compile { target { ! ia32 } } } */
/* { dg-options "-O2" } */
unsigned long long foo()
{
unsigned long long h,l;
asm volatile ("rdtsc": "=a" (l), "=d" (h));
return l | (h << 32);
}
/* { dg-final { scan-assembler-not "mov" } } */