On Tue, Oct 19, 2021 at 11:42 PM Uros Bizjak <ubiz...@gmail.com> wrote: > > On Tue, Oct 19, 2021 at 8:23 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > > > commit 247c407c83f0015f4b92d5f71e45b63192f6757e > > Author: Roger Sayle <ro...@nextmovesoftware.com> > > Date: Mon Oct 18 12:15:40 2021 +0100 > > > > Try placing RTL folded constants in the constant pool. > > > > My recent attempts to come up with a testcase for my patch to evaluate > > ss_plus in simplify-rtx.c, identified a missed optimization opportunity > > (that's potentially a long-time regression): The RTL optimizers no > > longer > > place constants in the constant pool. > > > > changed -m32 codegen from > > > > movq .LC1, %mm0 > > paddb .LC0, %mm0 > > movq %mm0, x > > ret > > > > to > > > > movl $807671820, %eax > > movl $1616136252, %edx > > movl %eax, x > > movl %edx, x+4 > > ret > > > > and -m64 codegen from > > > > movq .LC1(%rip), %mm0 > > paddb .LC0(%rip), %mm0 > > movq %xmm0, x(%rip) > > ret > > > > to > > > > movq .LC2(%rip), %rax > > movq %rax, x(%rip) > > ret > > > > Adjust pr22076.c to check that MMX register isn't used since avoiding > > MMX register isn't a bad thing. > > > > PR testsuite/102840 > > * gcc.target/i386/pr22076.c: Updated to check that MMX register > > isn't used. > > The compiler is now able to evaluate the result at the compile time > and it optimizes the test accordingly. Let's provide some MMX > instruction that is implemented with UNSPEC, so the compiler won't be > able to outsmart us. > > Something like the attached patch. > > Uros.
Works for me. Thanks. -- H.J.
