Hi, For some TARGET, like ARM THUMB1, the offset in load/store should be nature aligned. But in function get_address_cost, when computing max_offset, it only tries byte-aligned offsets:
((unsigned HOST_WIDE_INT) 1 << i) - 1 which can not meet thumb_legitimate_offset_p check called from thumb1_legitimate_address_p for HImode and SImode. The patch adds additional try for aligned offset: ((unsigned HOST_WIDE_INT) 1 << i) - GET_MODE_SIZE (address_mode). Bootstrap and no make check regression on X86-64. No make check regression on qemu for Cortex-m0 and Cortex-m3. For Cortex-m0, no performance changes with coremark and dhrystone. Coremark code size is ~0.44 smaller. And eembcv2 code size is ~0.22 smaller. CSiBE code size is ~0.05% smaller. OK for trunk? Thanks! -Zhenqiang ChangeLog 2014-08-04 Zhenqiang Chen <zhenqiang.c...@arm.com> * tree-ssa-loop-ivopts.c (get_address_cost): Try aligned offset. testsuite/ChangeLog: 2014-08-04 Zhenqiang Chen <zhenqiang.c...@arm.com> * gcc.target/arm/get_address_cost_aligned_max_offset.c: New test. diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c index 3b4a6cd..562122a 100644 --- a/gcc/tree-ssa-loop-ivopts.c +++ b/gcc/tree-ssa-loop-ivopts.c @@ -3308,6 +3308,18 @@ get_address_cost (bool symbol_present, bool var_present, XEXP (addr, 1) = gen_int_mode (off, address_mode); if (memory_address_addr_space_p (mem_mode, addr, as)) break; + /* For some TARGET, like ARM THUMB1, the offset should be nature + aligned. Try an aligned offset if address_mode is not QImode. */ + off = (address_mode == QImode) + ? 0 + : ((unsigned HOST_WIDE_INT) 1 << i) + - GET_MODE_SIZE (address_mode); + if (off > 0) + { + XEXP (addr, 1) = gen_int_mode (off, address_mode); + if (memory_address_addr_space_p (mem_mode, addr, as)) + break; + } } if (i == -1) off = 0; diff --git a/gcc/testsuite/gcc.target/arm/get_address_cost_aligned_max_offset.c b/gcc/testsuite/gcc.target/arm/get_address_cost_aligned_max_offset.c new file mode 100644 index 0000000..cc3e2f7 --- /dev/null +++ b/gcc/testsuite/gcc.target/arm/get_address_cost_aligned_max_offset.c @@ -0,0 +1,28 @@ +/* { dg-do compile } */ +/* { dg-options "-mthumb -O2" } */ +/* { dg-require-effective-target arm_thumb1_ok } */ + +unsigned int +test (const short p16[6 * 64]) +{ + unsigned int i = 6; + unsigned int ret = 0; + + do + { + unsigned long long *p64 = (unsigned long long*) p16; + unsigned int *p32 = (unsigned int*) p16; + ret += ret; + if (p16[1] || p32[1]) + ret++; + else if (p64[1] | p64[2] | p64[3]) + ret++; + p16 += 64; + i--; + } while (i != 0); + + return ret; +} + +/* { dg-final { scan-assembler-not "#22" } } */ +/* { dg-final { scan-assembler-not "#14" } } */