On Wed, May 15, 2019 at 6:30 AM bin.cheng <bin.ch...@linux.alibaba.com> wrote: > > Hi, > As noted in PR57534 comment #33, SLSR currently doesn't strength reduce memory > references in reported cases, which conflicts with its comment at the > beginning of file. > The main reason is in functions slsr_process_ref and restructure_reference > which > rejects MEM_REF by handled_compoenent_p in the first place. This patch > identifies > and creates CAND_REF for MEM_REF by restructuring base/offset. > > Note the patch only affects cases with multiple reducible MEM_REF. > > Also note, with this patch, [base + cst_offset] addressing mode would be > generally > preferred. I need to adjust three existing tests: > * gcc.dg/tree-ssa/isolate-5.c > * gcc.dg/tree-ssa/ssa-hoist-4.c > Though address computation is reduced out of memory reference, the generated > assembly is not worsened. > > * gcc.dg/tree-ssa/slsr-3.c > The generated assembly has two more instructions: > < movslq %edx, %rcx > < movl (%rsi,%rcx,4), %r9d > < leaq 0(,%rcx,4), %rax > < leal 2(%r9), %r8d > < movl %r8d, (%rdi,%rcx,4) > < movl 4(%rsi,%rax), %ecx > < addl $2, %ecx > < movl %ecx, 4(%rdi,%rax) > < movl 8(%rsi,%rax), %ecx > < addl $2, %ecx > < movl %ecx, 8(%rdi,%rax) > < movl 12(%rsi,%rax), %ecx > < addl $2, %ecx > < movl %ecx, 12(%rdi,%rax) > --- > > movslq %edx, %rax > > salq $2, %rax > > addq %rax, %rsi > > addq %rax, %rdi > > movl (%rsi), %eax > > addl $2, %eax > > movl %eax, (%rdi) > > movl 4(%rsi), %eax > > addl $2, %eax > > movl %eax, 4(%rdi) > > movl 8(%rsi), %eax > > addl $2, %eax > > movl %eax, 8(%rdi) > > movl 12(%rsi), %eax > > addl $2, %eax > > movl %eax, 12(%rdi) > > Seems to me this is not deteriorating and "salq" can be saved by two forward > propagation. > > Bootstrap and test on x86_64, any comments?
The idea is good I think and the result above as well. Leaving for Bill to have a look as well, otherwise OK. Thanks, Richard. > Thanks, > bin > > 2019-05-15 Bin Cheng <bin.ch...@linux.alibaba.com> > > PR tree-optimization/57534 > * gimple-ssa-strength-reduction.c (restructure_base_offset): New. > (restructure_reference): Call restructure_base_offset when offset is > NULL. > (slsr_process_ref): Handle MEM_REF. > > 2018-05-15 Bin Cheng <bin.ch...@linux.alibaba.com> > > PR tree-optimization/57534 > * gcc.dg/tree-ssa/pr57534.c: New test. > * gcc.dg/tree-ssa/isolate-5.c: Adjust checking strings. > * gcc.dg/tree-ssa/slsr-3.c: Ditto. > * gcc.dg/tree-ssa/ssa-hoist-4.c: Ditto.
