From: H.J. Lu Date: Tue, 17 Dec 2019 01:29:09 +0000 (-0800) Subject: Use add for a = a + b and a = b + a when possible. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=62dd2904f05ee752bbeff43a196b90ecd7b94616;p=gcc.git Use add for a = a + b and a = b + a when possible. Since except for Bonnell, 01 fb add %edi,%ebx is faster and shorter than 8d 1c 1f lea (%rdi,%rbx,1),%ebx we should use add for a = a + b and a = b + a when possible if not optimizing for Bonnell. Tested on x86-64. 2019-12-17 H.J. Lu gcc/ PR target/92807 * config/i386/i386.c (ix86_lea_outperforms): Check !TARGET_BONNELL. (ix86_avoid_lea_for_addr): When not optimizing for Bonnell, use add for a = a + b and a = b + a. gcc/testsuite/ PR target/92807 * gcc.target/i386/pr92807-1.c: New test. From-SVN: r279451 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 26dd71177e7..9a37d825362 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2019-12-17 H.J. Lu + + PR target/92807 + * config/i386/i386.c (ix86_lea_outperforms): Check !TARGET_BONNELL. + (ix86_avoid_lea_for_addr): When not optimizing for Bonnell, use add + for a = a + b and a = b + a. + 2019-12-16 Martin Sebor PR middle-end/92952 diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c index 551e77a855a..02f4d000c2b 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -14433,11 +14433,10 @@ ix86_lea_outperforms (rtx_insn *insn, unsigned int regno0, unsigned int regno1, { int dist_define, dist_use; - /* For Silvermont if using a 2-source or 3-source LEA for - non-destructive destination purposes, or due to wanting - ability to use SCALE, the use of LEA is justified. */ - if (TARGET_SILVERMONT || TARGET_GOLDMONT || TARGET_GOLDMONT_PLUS - || TARGET_TREMONT || TARGET_INTEL) + /* For Atom processors newer than Bonnell, if using a 2-source or + 3-source LEA for non-destructive destination purposes, or due to + wanting ability to use SCALE, the use of LEA is justified. */ + if (!TARGET_BONNELL) { if (has_scale) return true; @@ -14572,10 +14571,6 @@ ix86_avoid_lea_for_addr (rtx_insn *insn, rtx operands[]) struct ix86_address parts; int ok; - /* Check we need to optimize. */ - if (!TARGET_AVOID_LEA_FOR_ADDR || optimize_function_for_size_p (cfun)) - return false; - /* The "at least two components" test below might not catch simple move or zero extension insns if parts.base is non-NULL and parts.disp is const0_rtx as the only components in the address, e.g. if the @@ -14612,6 +14607,20 @@ ix86_avoid_lea_for_addr (rtx_insn *insn, rtx operands[]) if (parts.index) regno2 = true_regnum (parts.index); + /* Use add for a = a + b and a = b + a since it is faster and shorter + than lea for most processors. For the processors like BONNELL, if + the destination register of LEA holds an actual address which will + be used soon, LEA is better and otherwise ADD is better. */ + if (!TARGET_BONNELL + && parts.scale == 1 + && (!parts.disp || parts.disp == const0_rtx) + && (regno0 == regno1 || regno0 == regno2)) + return true; + + /* Check we need to optimize. */ + if (!TARGET_AVOID_LEA_FOR_ADDR || optimize_function_for_size_p (cfun)) + return false; + split_cost = 0; /* Compute how many cycles we will add to execution time diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 7272aba5dcc..4142c507e2a 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-12-17 H.J. Lu + + PR target/92807 + * gcc.target/i386/pr92807-1.c: New test. + 2019-12-16 Jozef Lawrynowicz * g++.dg/init/dso_handle1.C: Require cxa_atexit support. diff --git a/gcc/testsuite/gcc.target/i386/pr92807-1.c b/gcc/testsuite/gcc.target/i386/pr92807-1.c new file mode 100644 index 00000000000..00f92930af9 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr92807-1.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ + +unsigned int +abs2 (unsigned int a) +{ + unsigned int s = ((a>>15)&0x10001)*0xffff; + return (a+s)^s; +} + +/* { dg-final { scan-assembler-not "leal" } } */