From 11ba42eccc2bd0ce6d893b583a37dc0b46d09adf Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Wed, 24 Apr 2019 13:06:00 -0700
Subject: qbe: Make sure generated code doesn't depend on argument evaluation
 order

It would be correct in any order, but this is a bit simpler and guarantees
the same output.
---
 qbe.c                             | 8 +++-----
 test/bitfield-compound-assign.qbe | 8 ++++----
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/qbe.c b/qbe.c
index 68bc1b3..6dc7ff1 100644
--- a/qbe.c
+++ b/qbe.c
@@ -290,15 +290,13 @@ funcstore(struct func *f, struct type *t, enum typequal tq, struct lvalue lval,
 		}
 		if (lval.bits.before || lval.bits.after) {
 			mask = 0xffffffffffffffffu >> lval.bits.after + 64 - t->size * 8 ^ (1 << lval.bits.before) - 1;
-			v = funcinst(f, IOR, t->repr,
+			v = funcinst(f, ISHL, t->repr, v, mkintconst(&i32, lval.bits.before));
+			v = funcinst(f, IAND, t->repr, v, mkintconst(t->repr, mask));
+			v = funcinst(f, IOR, t->repr, v,
 				funcinst(f, IAND, t->repr,
 					funcinst(f, loadop, t->repr, lval.addr),
 					mkintconst(t->repr, ~mask),
 				),
-				funcinst(f, IAND, t->repr,
-					funcinst(f, ISHL, t->repr, v, mkintconst(&i32, lval.bits.before)),
-					mkintconst(t->repr, mask),
-				),
 			);
 		}
 		funcinst(f, storeop, NULL, v, lval.addr);
diff --git a/test/bitfield-compound-assign.qbe b/test/bitfield-compound-assign.qbe
index 829f5f6..5cc38de 100644
--- a/test/bitfield-compound-assign.qbe
+++ b/test/bitfield-compound-assign.qbe
@@ -10,10 +10,10 @@ function $f() {
 	%.6 =w shl %.5, 19
 	%.7 =w sar %.6, 23
 	%.8 =w add %.7, 3
-	%.9 =w loaduw %.4
-	%.10 =w and %.9, 18446744073709543439
-	%.11 =w shl %.8, 4
-	%.12 =w and %.11, 8176
+	%.9 =w shl %.8, 4
+	%.10 =w and %.9, 8176
+	%.11 =w loaduw %.4
+	%.12 =w and %.11, 18446744073709543439
 	%.13 =w or %.10, %.12
 	storew %.13, %.4
 	ret
-- 
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