lib/Target/Alpha/README.txt

   1 Fix jump table support.  currently it uses 64bit absolute address.
   2 gcc uses gprel32.  This way I won't keep fighting Evan as he keeps
   3 breaking 64bit entries in jump tables...
   4
   5 #include <string.h>
   6 #include <setjmp.h>
   7
   8 int main(int x, char** y)
   9 {
  10 char* foo;
  11 switch(x) {
  12 case 1:
  13 foo = "1";
  14 break;
  15 case 2:
  16 foo = "2";
  17 break;
  18 case 3:
  19 foo = "3";
  20 break;
  21 case 4:
  22 foo = "4";
  23 break;
  24 case 5:
  25 foo = "5";
  26 break;
  27 case 6:
  28 foo = "6";
  29 break;
  30 case 7:
  31 foo = "7";
  32 break;
  33 case 8:
  34 foo = "8";
  35 break;
  36 };
  37 print(foo);
  38 return 0;
  39
  40 }
  41
  42
  43         .set noreorder
  44         .set volatile
  45         .set noat
  46         .set nomacro
  47         .section        .rodata.str1.1,"aMS",@progbits,1
  48 $LC6:
  49         .ascii "7\0"
  50 $LC7:
  51         .ascii "8\0"
  52 $LC0:
  53         .ascii "1\0"
  54 $LC1:
  55         .ascii "2\0"
  56 $LC2:
  57         .ascii "3\0"
  58 $LC3:
  59         .ascii "4\0"
  60 $LC4:
  61         .ascii "5\0"
  62 $LC5:
  63         .ascii "6\0"
  64         .text
  65         .align 2
  66         .align 4
  67         .globl main
  68         .ent main
  69 main:
  70         .frame $30,16,$26,0
  71         .mask 0x4000000,-16
  72         ldah $29,0($27)         !gpdisp!1
  73         lda $29,0($29)          !gpdisp!1
  74 $main..ng:
  75         zapnot $16,15,$16
  76         lda $30,-16($30)
  77         cmpule $16,8,$1
  78         stq $26,0($30)
  79         .prologue 1
  80         beq $1,$L2
  81         ldah $6,$L11($29)               !gprelhigh
  82         lda $5,$L11($6)         !gprellow
  83         s4addq $16,$5,$0
  84         ldl $2,0($0)
  85         addq $29,$2,$3
  86         jmp $31,($3),$L2
  87         .section        .rodata
  88         .align 2
  89         .align 2
  90 $L11:
  91         .gprel32 $L2
  92         .gprel32 $L3
  93         .gprel32 $L4
  94         .gprel32 $L5
  95         .gprel32 $L6
  96         .gprel32 $L7
  97         .gprel32 $L8
  98         .gprel32 $L9
  99         .gprel32 $L10
 100         .text
 101 $L9:
 102         ldah $20,$LC6($29)              !gprelhigh
 103         lda $4,$LC6($20)                !gprellow
 104         .align 4
 105 $L2:
 106         mov $4,$16
 107         ldq $27,print($29)              !literal!2
 108         jsr $26,($27),print             !lituse_jsr!2
 109         ldah $29,0($26)         !gpdisp!3
 110         mov $31,$0
 111         bis $31,$31,$31
 112         lda $29,0($29)          !gpdisp!3
 113         ldq $26,0($30)
 114         lda $30,16($30)
 115         ret $31,($26),1
 116 $L10:
 117         ldah $21,$LC7($29)              !gprelhigh
 118         lda $4,$LC7($21)                !gprellow
 119         br $31,$L2
 120 $L3:
 121         ldah $7,$LC0($29)               !gprelhigh
 122         lda $4,$LC0($7)         !gprellow
 123         br $31,$L2
 124 $L4:
 125         ldah $8,$LC1($29)               !gprelhigh
 126         lda $4,$LC1($8)         !gprellow
 127         br $31,$L2
 128 $L5:
 129         ldah $16,$LC2($29)              !gprelhigh
 130         lda $4,$LC2($16)                !gprellow
 131         br $31,$L2
 132 $L6:
 133         ldah $17,$LC3($29)              !gprelhigh
 134         lda $4,$LC3($17)                !gprellow
 135         br $31,$L2
 136 $L7:
 137         ldah $18,$LC4($29)              !gprelhigh
 138         lda $4,$LC4($18)                !gprellow
 139         br $31,$L2
 140 $L8:
 141         ldah $19,$LC5($29)              !gprelhigh
 142         lda $4,$LC5($19)                !gprellow
 143         br $31,$L2
 144         .end main
 145         .section        .note.GNU-stack,"",@progbits
 146         .ident  "GCC: (GNU) 3.4.4 20050314 (prerelease) (Debian 3.4.3-13)"
 147
 148
 149
 150
 151 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 152 Fix Ordered/Unordered FP stuff
 153
 154
 155 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 156 improve bytezap opertunities
 157 ulong %foo(ulong %y) {
 158 entry:
 159         %tmp = and ulong %y,  65535
 160         %tmp2 = shr ulong %tmp,  ubyte 3
 161         ret ulong %tmp2
 162 }
 163
 164
 165 compiles to a 3 instruction sequence without instcombine
 166         zapnot $16,3,$0
 167         srl $0,3,$0
 168         ret $31,($26),1
 169
 170 After instcombine you get
 171 ulong %foo(ulong %y) {
 172 entry:
 173         %tmp = shr ulong %y, ubyte 3            ; <ulong> [#uses=1]
 174         %tmp2 = and ulong %tmp, 8191            ; <ulong> [#uses=1]
 175         ret ulong %tmp2
 176 }
 177
 178 which compiles to
 179         lda $0,8191($31)
 180         srl $16,3,$1
 181         and $1,$0,$0
 182         ret $31,($26),1
 183