[gcc r15-882] Reduce cost of MEM (A + imm).

[hongtao Liu via Gcc-cvs]

https://gcc.gnu.org/g:1d6199e5f8c1c08083eeb0279f71333234fe14ad

commit r15-882-g1d6199e5f8c1c08083eeb0279f71333234fe14ad
Author: liuhongt <hongtao....@intel.com>
Date:   Mon Feb 19 13:57:24 2024 +0800

    Reduce cost of MEM (A + imm).
    
    For MEM, rtx_cost iterates each subrtx, and adds up the costs,
    so for MEM (reg) and MEM (reg + 4), the former costs 5,
    the latter costs 9, it is not accurate for x86. Ideally
    address_cost should be used, but it reduce cost too much.
    So current solution is make constant disp as cheap as possible.
    
    gcc/ChangeLog:
    
            PR target/67325
            * config/i386/i386.cc (ix86_rtx_costs): Reduce cost of MEM (A
            + imm) to "cost of MEM (A)" + 1.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/i386/pr67325.c: New test.

Diff:
---
 gcc/config/i386/i386.cc                 | 18 +++++++++++++++++-
 gcc/testsuite/gcc.target/i386/pr67325.c |  7 +++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 3e2a3a194f1..85d87b9f778 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -22194,7 +22194,23 @@ ix86_rtx_costs (rtx x, machine_mode mode, int 
outer_code_i, int opno,
       /* An insn that accesses memory is slightly more expensive
          than one that does not.  */
       if (speed)
-        *total += 1;
+       {
+         *total += 1;
+         rtx addr = XEXP (x, 0);
+         /* For MEM, rtx_cost iterates each subrtx, and adds up the costs,
+            so for MEM (reg) and MEM (reg + 4), the former costs 5,
+            the latter costs 9, it is not accurate for x86. Ideally
+            address_cost should be used, but it reduce cost too much.
+            So current solution is make constant disp as cheap as possible.  */
+         if (GET_CODE (addr) == PLUS
+             && x86_64_immediate_operand (XEXP (addr, 1), Pmode))
+           {
+             *total += 1;
+             *total += rtx_cost (XEXP (addr, 0), Pmode, PLUS, 0, speed);
+             return true;
+           }
+       }
+
       return false;
 
     case ZERO_EXTRACT:
diff --git a/gcc/testsuite/gcc.target/i386/pr67325.c 
b/gcc/testsuite/gcc.target/i386/pr67325.c
new file mode 100644
index 00000000000..c3c1e4c5b4d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr67325.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-not "(?:sar|shr)" } } */
+
+int f(long*l){
+  return *l>>32;
+}