[hackers] [scc] [cc2-qbe] Add Sethi-Ullman number calculation || Roberto E. Vargas Caballero

From: <git_AT_suckless.org>
Date: Wed, 13 Apr 2016 08:11:39 +0200 (CEST)

commit 53e82078e4f9c8450ba94ba169cce9b51d513df2
Author: Roberto E. Vargas Caballero <roberto.vargas_AT_igrid-td.com>
AuthorDate: Tue Apr 12 17:16:50 2016 +0200
Commit: Roberto E. Vargas Caballero <roberto.vargas_AT_igrid-td.com>
CommitDate: Tue Apr 12 17:16:50 2016 +0200

    [cc2-qbe] Add Sethi-Ullman number calculation
    
    In the case of QBE we can ignore the addressability, and we only
    use it for the Sethi-Ullman number generation

diff --git a/cc2/arch/qbe/cgen.c b/cc2/arch/qbe/cgen.c
index 54e3ed2..43236e1 100644
--- a/cc2/arch/qbe/cgen.c
+++ b/cc2/arch/qbe/cgen.c
_AT_@ -7,7 +7,58 @@ generate(void)
 {
 }
 
+/*
+ * This is strongly influenced by
+ * http://plan9.bell-labs.com/sys/doc/compiler.ps (/sys/doc/compiler.ps)
+ * calculate addresability as follows
+ * AUTO => 11 value+fp
+ * REG => 11 reg
+ * STATIC => 11 (value)
+ * CONST => 11 $value
+ * These values of addressability are not used in the code generation.
+ * They are only used to calculate the Sethi-Ullman numbers. Since
+ * QBE is AMD64 targered we could do a better job here, and try to
+ * detect some of the complex addressing modes of these processors.
+ */
 Node *
 sethi(Node *np)
 {
+ Node *lp, *rp;
+
+ if (!np)
+ return np;
+
+ np->complex = 0;
+ np->address = 0;
+ lp = np->left;
+ rp = np->right;
+
+ switch (np->op) {
+ case AUTO:
+ case REG:
+ case MEM:
+ case CONST:
+ np->address = 11;
+ break;
+ default:
+ sethi(lp);
+ sethi(rp);
+ break;
+ }
+
+ if (np->address > 10)
+ return np;
+ if (lp)
+ rp->complex = lp->complex;
+ if (rp) {
+ int d = np->complex - rp->complex;
+
+ if (d == 0)
+ ++np->complex;
+ else if (d < 0)
+ np->complex = rp->complex;
+ }
+ if (np->complex == 0)
+ ++rp->complex;
+ return np;
 }
diff --git a/cc2/arch/z80/cgen.c b/cc2/arch/z80/cgen.c
index 567d209..95067f9 100644
--- a/cc2/arch/z80/cgen.c
+++ b/cc2/arch/z80/cgen.c
_AT_@ -42,10 +42,8 @@ sethi(Node *np)
                 np->address = 20;
                 break;
         default:
- if (lp)
- sethi(lp);
- if (rp)
- sethi(rp);
+ sethi(lp);
+ sethi(rp);
                 break;
         }
 
Received on Wed Apr 13 2016 - 08:11:39 CEST

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