qbe

commit 660a8d9dfa44050897b2f5ead823554893d79f24
parent 0384d73e8daa5c948fb08c7301144c0d7e740ef9
Author: Quentin Carbonneaux <quentin@c9x.me>
Date:   Mon, 29 Apr 2019 11:29:22 +0200

fix folding of unsigned operations

This fixes similar bugs than the ones fixed
in the previous commit.

In the folding code the invariant is that
when a result is 32 bits wide, the low 32
bits of 'x' are correct.  The high bits
can be anything.

Diffstat:
M
fold.c
 | 
6
+++---
M
test/fold1.ssa
 | 
26
++++++++++++++++++++++++--

2 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/fold.c b/fold.c
@@ -373,14 +373,14 @@ foldint(Con *res, int op, int w, Con *cl, Con *cr)
 	case Osub:  x = l.u - r.u; break;
 	case Odiv:  x = w ? l.s / r.s : (int32_t)l.s / (int32_t)r.s; break;
 	case Orem:  x = w ? l.s % r.s : (int32_t)l.s % (int32_t)r.s; break;
-	case Oudiv: x = l.u / r.u; break;
-	case Ourem: x = l.u % r.u; break;
+	case Oudiv: x = w ? l.u / r.u : (uint32_t)l.u / (uint32_t)r.u; break;
+	case Ourem: x = w ? l.u % r.u : (uint32_t)l.u % (uint32_t)r.u; break;
 	case Omul:  x = l.u * r.u; break;
 	case Oand:  x = l.u & r.u; break;
 	case Oor:   x = l.u | r.u; break;
 	case Oxor:  x = l.u ^ r.u; break;
 	case Osar:  x = (w ? l.s : (int32_t)l.s) >> (r.u & 63); break;
-	case Oshr:  x = l.u >> (r.u & 63); break;
+	case Oshr:  x = (w ? l.u : (uint32_t)l.u) >> (r.u & 63); break;
 	case Oshl:  x = l.u << (r.u & 63); break;
 	case Oextsb: x = (int8_t)l.u;   break;
 	case Oextub: x = (uint8_t)l.u;  break;
diff --git a/test/fold1.ssa b/test/fold1.ssa
@@ -19,7 +19,29 @@ function w $f3() {
 	ret %x
 }
 
+export
+function w $f4() {
+@start
+	%x =w shr 4294967296, 1  # 2^32 >> 1
+	ret %x
+}
+
+export
+function w $f5() {
+@start
+	%x =w udiv 1, 4294967297  # 1 / (2^32 + 1)
+	ret %x
+}
+
+export
+function w $f6() {
+@start
+	%x =w urem 4294967296, 7  # 2^32 % 7
+	ret %x
+}
+
 # >>> driver
-# extern int f1(), f2(), f3();
-# int main() { return !(f1() == -1 && f2() == -32 && f3() == -5); }
+# extern int f1(), f2(), f3(), f4(), f5(), f6();
+# int main() { return !(f1() == -1 && f2() == -32 && f3() == -5 &&
+#                       f4() == 0 && f5() == 1 && f6() == 0); }
 # <<<