Comment 9 for bug 1295738

Reverting this patch in 209897 bug still occurs in trunk with -mno-lra.

SPILL failure occurs for regno 110 ("dst" operand) in below instruction

(insn 634 633 635 27 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 110 [ dst ]) <== This operand r5 is registers gets assigned
                        (reg/v:SI 112 [ op2 ]))
                    (eq:SI (reg/v:SI 110 [ dst ]) <== This operand
                        (reg/v:SI 111 [ op1 ]))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 300 {*ior_scc_scc

First observation is that reload is not able to reuse "r5" that was used in second reload in operation for the same register id 110 "dst"

The IRA Dump shows.

(insn 632 631 633 27 (set (reg:SI 1 r1)
        (reg/v:SI 110 [ dst ])) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 667 {*thumb2_movsi_vfp}
     (nil))
(insn 633 632 634 27 (set (reg:SI 2 r2)
        (const_int 0 [0])) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 667 {*thumb2_movsi_vfp}
     (nil))
(insn 634 633 635 27 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 110 [ dst ])
                        (reg/v:SI 112 [ op2 ]))
                    (eq:SI (reg/v:SI 110 [ dst ])
                        (reg/v:SI 111 [ op1 ]))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 300 {*ior_scc_scc}

The register operand 110 "dst" is already passed as argument 1 and hence gets register r1. See insn 632.

But this is not reused by insn 634.

However there are some other places in IRA dump where the same expression occurs and there register r1 is used. Here operand "dst" 110 is marked as dead.

(insn 431 430 433 24 (set (reg:SI 1 r1)
        (reg/v:SI 110 [ dst ])) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:388 667 {*thumb2_movsi_vfp}
     (expr_list:REG_DEAD (reg/v:SI 110 [ dst ])
        (nil)))

(insn 433 431 432 24 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 112 [ op ])
                        (reg:SI 1 r1))
                    (eq:SI (reg/v:SI 111 [ op ])
                        (reg:SI 1 r1))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:388 300 {*ior_scc_scc

Still working on why IRA is not replacing the operand with R1 here, but replaces in other places.