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This commit is contained in:
ceriel
1990-06-20 10:05:22 +00:00
parent 955002df6c
commit d3a17633aa
25 changed files with 583 additions and 456 deletions
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17
doc/ego/sr/sr1
View File

@@ -16,13 +16,16 @@ done by the EM Peephole Optimizer.
Strength reduction can also be applied
more generally to operators used in a loop.
.DS
i := 1; i := 1;
while i < 100 loop --> TMP := i * 118;
put(i * 118); while i < 100 loop
i := i + 1; put(TMP);
end loop; i := i + 1;
TMP := TMP + 118;
end loop;
.TS
l l.
i := 1; i := 1;
while i < 100 loop\ \ \ \ \ \ \ --> TMP := i * 118;
put(i * 118); while i < 100 loop
i := i + 1; put(TMP);
end loop; i := i + 1;
TMP := TMP + 118;
end loop;
.TE
Fig. 6.1 An example of Strenght Reduction
.DE

36
doc/ego/sr/sr2
View File

@@ -105,11 +105,11 @@ iv_expression * constant
.IP (2)
constant * iv_expression
.IP (3)
A[iv-expression] := (assign to array element)
A[iv-expression] := \kx(assign to array element)
.IP (4)
A[iv-expression] (use array element)
A[iv-expression] \h'|\nxu'(use array element)
.IP (5)
& A[iv-expression] (take address of array element)
& A[iv-expression] \h'|\nxu'(take address of array element)
.LP
(Note that EM has different instructions to use an array element,
store into one, or take the address of one, resp. LAR, SAR, and AAR).
@@ -171,10 +171,13 @@ replaced by TMP.
For array optimizations, the replacement
depends on the form:
.DS
\fIform\fR \fIreplacement\fR
(3) A[iv-expr] := *TMP := (assign indirect)
(4) A[iv-expr] *TMP (use indirect)
(5) &A[iv-expr] TMP
.TS
l l l.
\fIform\fR \fIreplacement\fR
(3) A[iv-expr] := *TMP := (assign indirect)
(4) A[iv-expr] *TMP (use indirect)
(5) &A[iv-expr] TMP
.TE
.DE
The '*' denotes the indirect operator. (Note that
EM has different instructions to do
@@ -199,14 +202,17 @@ must be negated.
.PP
The transformations are demonstrated by an example.
.DS
i := 100; i := 100;
while i > 1 loop TMP := (6-i) * 5;
X := (6-i) * 5 + 2; while i > 1 loop
Y := (6-i) * 5 - 8; --> X := TMP + 2;
i := i - 3; Y := TMP - 8;
end loop; i := i - 3;
TMP := TMP + 15;
end loop;
.TS
l l.
i := 100; i := 100;
while i > 1 loop TMP := (6-i) * 5;
X := (6-i) * 5 + 2; while i > 1 loop
Y := (6-i) * 5 - 8;\ \ \ \ \ \ \ --> X := TMP + 2;
i := i - 3; Y := TMP - 8;
end loop; i := i - 3;
TMP := TMP + 15;
end loop;
.TE
Fig. 6.2 Example of complex Strength Reduction transformations
.DE

104
doc/ego/sr/sr3
View File

@@ -64,12 +64,15 @@ The assignment must match one of the EM patterns below.
('x' is the candidate. 'ws' is the word size of the target machine.
'n' is any number.)
.DS
\fIpattern\fR \fIstep size\fR
INL x | +1
DEL x | -1
LOL x ; (INC | DEC) ; STL x | +1 | -1
LOL x ; LOC n ; (ADI ws | SBI ws) ; STL x | +n | -n
LOC n ; LOL x ; ADI ws ; STL x. +n
.TS
l l.
\fIpattern\fR \fIstep size\fR
INL x | +1
DEL x | -1
LOL x ; (INC | DEC) ; STL x | +1 | -1
LOL x ; LOC n ; (ADI ws | SBI ws) ; STL x | +n | -n
LOC n ; LOL x ; ADI ws ; STL x +n
.TE
.DE
From the patterns the step size of the induction variable
can also be determined.
@@ -95,19 +98,22 @@ code in front of it.
If an expression is to be optimized, it must
be generated by the following syntax rules.
.DS
optimizable_expr:
iv_expr const mult |
const iv_expr mult |
address iv_expr address array_instr;
mult:
MLI ws |
MLU ws ;
array_instr:
LAR ws |
SAR ws |
AAR ws ;
const:
LOC n ;
.TS
l l.
optimizable_expr:
iv_expr const mult |
const iv_expr mult |
address iv_expr address array_instr;
mult:
MLI ws |
MLU ws ;
array_instr:
LAR ws |
SAR ws |
AAR ws ;
const:
LOC n ;
.TE
.DE
An 'address' is an EM instruction that loads an
address on the stack.
@@ -120,36 +126,42 @@ instructions like LDL are an 'address'.
denote resp. the array address and the
array descriptor address).
.DS
address:
LAE |
LAL |
LOL if ps=ws |
LOE ,, |
LIL ,, |
LDL if ps=2*ws |
LDE ,, ;
.TS
l l.
address:
LAE |
LAL |
LOL if ps=ws |
LOE ,, |
LIL ,, |
LDL if ps=2*ws |
LDE ,, ;
.TE
.DE
The notion of an iv-expression was introduced earlier.
.DS
iv_expr:
iv_expr unair_op |
iv_expr iv_expr binary_op |
loopconst |
iv ;
unair_op:
NGI ws |
INC |
DEC ;
binary_op:
ADI ws |
ADU ws |
SBI ws |
SBU ws ;
loopconst:
const |
LOL x if x is not changed in loop ;
iv:
LOL x if x is an induction variable ;
.TS
l l.
iv_expr:
iv_expr unair_op |
iv_expr iv_expr binary_op |
loopconst |
iv ;
unair_op:
NGI ws |
INC |
DEC ;
binary_op:
ADI ws |
ADU ws |
SBI ws |
SBU ws ;
loopconst:
const |
LOL x if x is not changed in loop ;
iv:
LOL x if x is an induction variable ;
.TE
.DE
An iv_expression must satisfy one additional constraint:
it must use exactly one operand that is an induction