[gcc r12-6118] i386: Check AX input in any_mul_highpart peepholes

[gcc r12-6118] i386: Check AX input in any_mul_highpart peepholes

[H.J. Lu]

https://gcc.gnu.org/g:d87483015d476a95f521f0c9dcf6988ca889063b

commit r12-6118-gd87483015d476a95f521f0c9dcf6988ca889063b
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri Dec 24 12:50:21 2021 -0800

    i386: Check AX input in any_mul_highpart peepholes
    
    When applying peephole optimization to transform
    
            mov imm, %reg0
            mov %reg1, %AX_REG
            imul %reg0
    
    to
    
            mov imm, %AX_REG
            imul %reg1
    
    disable peephole optimization if reg1 == AX_REG.
    
    gcc/
    
            PR target/103785
            * config/i386/i386.md: Swap operand order in comments and check
            AX input in any_mul_highpart peepholes.
    
    gcc/testsuite/
    
            PR target/103785
            * gcc.target/i386/pr103785.c: New test.

Diff:
---
 gcc/config/i386/i386.md                  | 10 ++++++---
 gcc/testsuite/gcc.target/i386/pr103785.c | 38 ++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 284b9507466..eea5d5d3f01 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -8578,7 +8578,7 @@
    (set_attr "mode" "SI")])
 
 ;; Highpart multiplication peephole2s to tweak register allocation.
-;; mov %rdx,imm; mov %rax,%rdi; imulq %rdx  ->  mov %rax,imm; imulq %rdi
+;; mov imm,%rdx; mov %rdi,%rax; imulq %rdx  ->  mov imm,%rax; imulq %rdi
 (define_peephole2
   [(set (match_operand:SWI48 0 "general_reg_operand")
 	(match_operand:SWI48 1 "immediate_operand"))
@@ -8588,7 +8588,8 @@
 		   (any_mul_highpart:SWI48 (match_dup 2) (match_dup 0)))
 	      (clobber (match_dup 2))
 	      (clobber (reg:CC FLAGS_REG))])]
-  "REGNO (operands[0]) != REGNO (operands[2])
+  "REGNO (operands[3]) != AX_REG
+   && REGNO (operands[0]) != REGNO (operands[2])
    && REGNO (operands[0]) != REGNO (operands[3])
    && (REGNO (operands[0]) == REGNO (operands[4])
        || peep2_reg_dead_p (3, operands[0]))"
@@ -8608,7 +8609,10 @@
 		     (any_mul_highpart:SI (match_dup 2) (match_dup 0))))
 	      (clobber (match_dup 2))
 	      (clobber (reg:CC FLAGS_REG))])]
-  "REGNO (operands[0]) != REGNO (operands[2])
+  "TARGET_64BIT
+   && REGNO (operands[3]) != AX_REG
+   && REGNO (operands[0]) != REGNO (operands[2])
+   && REGNO (operands[2]) != REGNO (operands[3])
    && REGNO (operands[0]) != REGNO (operands[3])
    && (REGNO (operands[0]) == REGNO (operands[4])
        || peep2_reg_dead_p (3, operands[0]))"
diff --git a/gcc/testsuite/gcc.target/i386/pr103785.c b/gcc/testsuite/gcc.target/i386/pr103785.c
new file mode 100644
index 00000000000..5503b965256
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103785.c
@@ -0,0 +1,38 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <stdlib.h>
+
+struct wrapper_t
+{
+  long k;
+  long e;
+};
+
+struct wrapper_t **table;
+
+__attribute__ ((weak, regparm (2)))
+void
+update (long k, long e)
+{
+  struct wrapper_t *elmt;
+
+  elmt = table[k % 3079];
+  if (elmt == 0)
+    return;
+  elmt->e = e;
+}
+
+int
+main ()
+{
+  table = (struct wrapper_t **) malloc (20 * sizeof (struct wrapper_t *));
+  for (int i = 0; i < 20; i++)
+    table[i] = (struct wrapper_t *) calloc (sizeof (struct wrapper_t), 1);
+  if (table[10]->e != 0)
+    abort ();
+  update (10, 20);
+  if (table[10]->e != 20)
+    abort ();
+  return 0;
+}