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ref: c4ad409e2756b66cd9c8c8ffb4ecd7e11605b7db
parent: 66cc3768c1a4d898bd0fbf9f2e5cde7779d3ef9b
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Sat Mar 13 08:56:40 EST 2021 

5c, 6c, 7c, 8c, kc, qc, vc: use explicit gmove(... , nn) in cgen() for result of OAS*, OPREINC, OPOSTINC

The expression value of the assignment operation was
returned implicitely by relying on regalloc() on the
right hand side "nod" borrowing the register from nn.

But this only works if nn is a register.

In case of 6c, it can also be a ONAME from a .safe
rathole returned by regsalloc().

This change adds explicit gmove() calls to assign the
expression value. Note that gmove() checks if source
and destination are the same register so it wont emit
redundant move operations in the common case.

The same is applied also to OPREINC and OPOSTINC operations.


--- a/sys/src/cmd/5c/cgen.c
+++ b/sys/src/cmd/5c/cgen.c
@@ -113,6 +113,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
@@ -251,7 +253,8 @@
 			gopcode(OAS, &nod2, Z, &nod);
 			gopcode(o, r, Z, &nod);
 			gopcode(OAS, &nod, Z, &nod2);
-	
+			if(nn != Z)
+				gmove(&nod, nn);
 			regfree(&nod);
 			if(l->addable < INDEXED)
 				regfree(&nod2);
@@ -472,6 +475,8 @@
 
 		regalloc(&nod, l, nn);
 		gopcode(OAS, &nod2, Z, &nod);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regalloc(&nod1, l, Z);
 		if(typefd[l->type->etype]) {
 			regalloc(&nod3, l, Z);
@@ -524,9 +529,11 @@
 		} else
 			gopcode(OADD, nodconst(v), Z, &nod);
 		gopcode(OAS, &nod, Z, &nod2);
-		if(nn && l->op == ONAME)	/* in x=++i, emit USED(i) */
-			gins(ANOP, l, Z);
-
+		if(nn != Z){
+			gmove(&nod, nn);
+			if(l->op == ONAME)	/* in x=++i, emit USED(i) */
+				gins(ANOP, l, Z);
+		}
 		regfree(&nod);
 		if(l->addable < INDEXED)
 			regfree(&nod2);
--- a/sys/src/cmd/6c/cgen.c
+++ b/sys/src/cmd/6c/cgen.c
@@ -112,6 +112,8 @@
 		if(l->complex >= r->complex) {
 			if(l->op == OINDEX && immconst(r)) {
 				gmove(r, l);
+				if(nn != Z)
+					gmove(r, nn);
 				break;
 			}
 			reglcgen(&nod1, l, Z);
@@ -130,6 +132,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
--- a/sys/src/cmd/7c/cgen.c
+++ b/sys/src/cmd/7c/cgen.c
@@ -128,6 +128,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
@@ -267,7 +269,8 @@
 			gopcode(OAS, &nod2, Z, &nod);
 			gopcode(o, r, Z, &nod);
 			gopcode(OAS, &nod, Z, &nod2);
-	
+			if(nn != Z)
+				gmove(&nod, nn);
 			regfree(&nod);
 			if(l->addable < INDEXED)
 				regfree(&nod2);
@@ -528,6 +531,8 @@
 
 		regalloc(&nod, l, nn);
 		gopcode(OAS, &nod2, Z, &nod);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regalloc(&nod1, l, Z);
 		if(typefd[l->type->etype]) {
 			regalloc(&nod3, l, Z);
@@ -580,9 +585,11 @@
 		} else
 			gopcode(OADD, nodconst(v), Z, &nod);
 		gopcode(OAS, &nod, Z, &nod2);
-		if(nn && l->op == ONAME)	/* in x=++i, emit USED(i) */
-			gins(ANOP, l, Z);
-
+		if(nn != Z){
+			gmove(&nod, nn);
+			if(l->op == ONAME)	/* in x=++i, emit USED(i) */
+				gins(ANOP, l, Z);
+		}
 		regfree(&nod);
 		if(l->addable < INDEXED)
 			regfree(&nod2);
--- a/sys/src/cmd/8c/cgen.c
+++ b/sys/src/cmd/8c/cgen.c
@@ -131,6 +131,8 @@
 		if(l->complex >= r->complex) {
 			if(l->op == OINDEX && r->op == OCONST) {
 				gmove(r, l);
+				if(nn != Z)
+					gmove(r, nn);
 				break;
 			}
 			reglcgen(&nod1, l, Z);
@@ -149,6 +151,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
--- a/sys/src/cmd/kc/cgen.c
+++ b/sys/src/cmd/kc/cgen.c
@@ -107,6 +107,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
@@ -423,6 +425,8 @@
 
 		regalloc(&nod, l, nn);
 		gopcode(OAS, &nod2, Z, &nod);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regalloc(&nod1, l, Z);
 		if(typefd[l->type->etype]) {
 			regalloc(&nod3, l, Z);
@@ -475,9 +479,11 @@
 		} else
 			gopcode(OADD, nodconst(v), Z, &nod);
 		gopcode(OAS, &nod, Z, &nod2);
-		if(nn && l->op == ONAME)	/* in x=++i, emit USED(i) */
-			gins(ANOP, l, Z);
-
+		if(nn != Z){
+			gmove(&nod, nn);
+			if(l->op == ONAME)	/* in x=++i, emit USED(i) */
+				gins(ANOP, l, Z);
+		}
 		regfree(&nod);
 		if(l->addable < INDEXED)
 			regfree(&nod2);
--- a/sys/src/cmd/qc/cgen.c
+++ b/sys/src/cmd/qc/cgen.c
@@ -109,6 +109,8 @@
 				regalloc(&nod, r, nn);
 				cgen(r, &nod);
 				gmove(&nod, l);
+				if(nn != Z)
+					gmove(&nod, nn);
 				regfree(&nod);
 			} else
 				gmove(r, l);
@@ -131,6 +133,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
--- a/sys/src/cmd/vc/cgen.c
+++ b/sys/src/cmd/vc/cgen.c
@@ -107,6 +107,8 @@
 			reglcgen(&nod1, l, Z);
 		}
 		gmove(&nod, &nod1);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regfree(&nod);
 		regfree(&nod1);
 		break;
@@ -425,6 +427,8 @@
 
 		regalloc(&nod, l, nn);
 		gopcode(OAS, &nod2, Z, &nod);
+		if(nn != Z)
+			gmove(&nod, nn);
 		regalloc(&nod1, l, Z);
 		if(typefd[l->type->etype]) {
 			regalloc(&nod3, l, Z);
@@ -477,9 +481,11 @@
 		} else
 			gopcode(OADD, nodconst(v), Z, &nod);
 		gopcode(OAS, &nod, Z, &nod2);
-		if(nn && l->op == ONAME)	/* in x=++i, emit USED(i) */
-			gins(ANOP, l, Z);
-
+		if(nn != Z) {
+			gmove(&nod, nn);
+			if(l->op == ONAME)	/* in x=++i, emit USED(i) */
+				gins(ANOP, l, Z);
+		}
 		regfree(&nod);
 		if(l->addable < INDEXED)
 			regfree(&nod2);
-- 
⑨