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remove unneeded limit register

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This commit is contained in:
Jörg Thalheim 2013-12-13 10:36:19 +01:00
parent b7399b014b
commit 588ee8b710
3 changed files with 34 additions and 31 deletions
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5
bericht.tex
View File

@ -52,8 +52,8 @@
\begin{lstlisting} \begin{lstlisting}
typedef uint32_t u32; typedef uint32_t u32;
void heron_sqrt(u32 *mem) { void heron_sqrt(u32 *mem) {
int i; int i = mem[0];
for (i = 1; i <= mem[0]; i++){ while (i > 0) {
u32 s = mem[i]; u32 s = mem[i];
if (s > 1) { if (s > 1) {
// x_0 = (s + 1) / 2 // x_0 = (s + 1) / 2
@ -71,6 +71,7 @@ void heron_sqrt(u32 *mem) {
} }
mem[i] = x; mem[i] = x;
} }
i--;
} }
} }
\end{lstlisting} \end{lstlisting}

53
graph.dot
View File

@ -2,19 +2,17 @@
digraph heron { digraph heron {
//node [shape=circle,regular=1,style=filled,fillcolor=white]; //node [shape=circle,regular=1,style=filled,fillcolor=white];
edge [arrowhead=odot]; edge [arrowhead=odot];
graph [overlap=false]; graph [overlap=scale];
subgraph { subgraph {
edge [weight=3]; edge [weight=3];
C0 -> C1 -> C2 -> C3 -> C4 -> C5 -> C6 -> C7 -> C8 -> C9 C0 -> C1 -> C2 -> C3 -> C4 -> C5 -> C6 -> C7 -> C8 -> C9 [minlen=3.5];
} }
// variables & constants // variables & constants
mem_0 [label="mem[0]"]; mem_0 [label="mem[0]"];
mem_i [label="mem[i]"]; mem_i [label="mem[i]"];
mem_i2 [label="mem[i]"]; mem_i2 [label="mem[i]",shape="box"];
i [ ]; i [label="i"];
1 [ ]; 1 [ ];
"1a" [label="1" ]; "1a" [label="1" ];
"1b" [label="1" ]; "1b" [label="1" ];
@ -24,29 +22,31 @@ digraph heron {
// operands // operands
s_shift_1 [label=">>",]; s_shift_1 [label=">>",];
i_lte_mem_0 [label=">=",]; i_lt_0 [label=">",];
// i <= mem[0] // i <= mem[0]
mem_0 -> i_lte_mem_0; mem_0 -> i:n [label="C0",style=dotted];
i -> i_lte_mem_0;
{ rank=same; C1; i_lte_mem_0; } 0 -> i_lt_0;
{ rank=same; C0; i; mem_0;} i -> i_lt_0;
{ rank=same; C0; i}
{ rank=same; C1; i_lt_0; }
// if (i <= mem[0]) -> // if (i <= mem[0]) ->
i_lte_mem_0 -> mem_s_gte_1 [style=dotted, arrowhead=normal,label="True",lhead=cluster_i_lte_mem_0]; i_lt_0 -> mem_s_gte_1 [style=dotted, arrowhead=normal,label="True"];
// else // else
i_lte_mem_0 -> Finish [style=dotted, arrowhead=normal,label="False",lhead=cluster_i_lte_mem_0]; i_lt_0 -> Finish [style=dotted, arrowhead=normal,label="False"];
{ rank=same; C9; Finish;} { rank=same; C9; Finish;}
subgraph i_lte_mem_0 { subgraph i_lt_0 {
mem_s_gte_1 [label=">"]; mem_s_gte_1 [label=">"];
s_div_x [label="/",]; s_div_x [label="/",];
new_x [label="+",]; new_x [label="+",];
s_div_x_shift_1 [label=">>",]; s_div_x_shift_1 [label=">>",];
x_shift_1 [label=">>",]; x_shift_1 [label=">>",];
old_x_lte_new_x [label="¹>=",]; old_x_lte_new_x [label=">=",];
inc_i [label="+",]; dec_i [label="-",];
// (s > 1) // (s > 1)
mem_i -> mem_s_gte_1; mem_i -> mem_s_gte_1;
@ -56,16 +56,17 @@ digraph heron {
// if (s > 1) // if (s > 1)
mem_s_gte_1 -> s_shift_1 [style=dotted,arrowhead=normal,label="True"]; mem_s_gte_1 -> s_shift_1 [style=dotted,arrowhead=normal,label="True"];
// else // else
mem_s_gte_1 -> inc_i [style=dotted,arrowhead=normal,label="False"]; mem_s_gte_1 -> dec_i [style=dotted,arrowhead=normal,label="False"];
subgraph if_mem_i_gte_1 { subgraph if_mem_i_gte_1 {
// x = s >> 1 // x = s >> 1
mem_i -> s_shift_1; mem_i -> s_shift_1;
1 -> s_shift_1; 1 -> s_shift_1;
s_shift_1 -> x; s_shift_1 -> x [style=dotted,arrowhead=normal,label="C2->C3"];
{ rank=same; C3; s_shift_1; x} { rank=same; C3; s_shift_1; x}
// (x >> 1) // (x >> 1)
x [shape="box"];
x -> x_shift_1; x -> x_shift_1;
"1a" -> x_shift_1; "1a" -> x_shift_1;
// (s/x) // (s/x)
@ -86,20 +87,20 @@ digraph heron {
// (old_x <= X) // (old_x <= X)
x -> old_x_lte_new_x; x -> old_x_lte_new_x;
new_x -> old_x_lte_new_x; new_x -> old_x_lte_new_x;
new_x -> x [style=dotted,label="if(¹)"]; new_x -> x [style=dotted,label="C7->C3"];
{ rank=same; C7; old_x_lte_new_x;} { rank=same; C7; old_x_lte_new_x;}
// if (old_x <= X) // if (old_x <= X)
old_x_lte_new_x -> inc_i [style=dotted,arrowhead=normal,label="True"]; old_x_lte_new_x -> dec_i [style=dotted,arrowhead=normal,label="True"];
// else // else
old_x_lte_new_x -> x [style=dotted,arrowhead=normal,label="False"];
"1c" -> dec_i;
"1c" -> inc_i; i -> dec_i:ne;
i -> inc_i:ne; dec_i:s -> i:s;
inc_i:s -> i:s; new_x -> mem_i2 [label="C7->C8", style=dotted];
new_x -> mem_i2 [label="if(¹)", style=dotted]; { rank=same; C8; dec_i; mem_i2};
{ rank=same; C8; inc_i; mem_i2};
} }
} }
} }

5
sqrt.c
View File

@ -7,8 +7,8 @@
typedef uint32_t u32; typedef uint32_t u32;
void heron_sqrt(u32 *mem) { void heron_sqrt(u32 *mem) {
int i; int i = mem[0];
for (i = 1; i <= mem[0]; i++){ while (i > 0) {
u32 s = mem[i]; u32 s = mem[i];
if (s > 1) { if (s > 1) {
// x_0 = (s + 1) / 2 // x_0 = (s + 1) / 2
@ -26,6 +26,7 @@ void heron_sqrt(u32 *mem) {
} }
mem[i] = x; mem[i] = x;
} }
i--;
} }
} }