2 files changed, 195 insertions, 1 deletions
diff --git a/simplify.c b/simplify.c
index 80c3cebc..d9c74bae 100644
--- a/simplify.c
+++ b/simplify.c
@@ -570,7 +570,10 @@ static long long check_shift_count(struct instruction *insn, unsigned long long
 
 static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long value)
 {
+	struct instruction *def;
+	unsigned long long nval;
 	unsigned int size;
+	pseudo_t src2;
 
 	if (!value)
 		return replace_with_pseudo(insn, pseudo);
@@ -583,15 +586,57 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v
 	case OP_ASR:
 		if (value >= size)
 			return 0;
+		if (pseudo->type != PSEUDO_REG)
+			break;
+		def = pseudo->def;
+		switch (def->opcode) {
+		case OP_ASR:
+			if (def == insn)	// cyclic DAG!
+				break;
+			src2 = def->src2;
+			if (src2->type != PSEUDO_VAL)
+				break;
+			nval = src2->value;
+			if (nval > insn->size)
+				break;
+			value += nval;
+			if (value >= size)
+				value = size - 1;
+			goto new_value;
+		}
 		break;
 	case OP_LSR:
 		size = operand_size(insn, pseudo);
 		/* fall through */
 	case OP_SHL:
 		if (value >= size)
-			return replace_with_pseudo(insn, value_pseudo(0));
+			goto zero;
+		if (pseudo->type != PSEUDO_REG)
+			break;
+		def = pseudo->def;
+		if (def->opcode == insn->opcode) {
+			if (def == insn)	// cyclic DAG!
+				break;
+			src2 = def->src2;
+			if (src2->type != PSEUDO_VAL)
+				break;
+			nval = src2->value;
+			if (nval > insn->size)
+				break;
+			value += nval;
+			goto new_value;
+		}
+		break;
 	}
 	return 0;
+
+new_value:
+	if (value < size) {
+		insn->src2 = value_pseudo(value);
+		return replace_pseudo(insn, &insn->src1, pseudo->def->src1);
+	}
+zero:
+	return replace_with_pseudo(insn, value_pseudo(0));
 }
 
 static int simplify_mul_div(struct instruction *insn, long long value)
diff --git a/validation/optim/shift-shift.c b/validation/optim/shift-shift.c
new file mode 100644
index 00000000..12a4b7d4
--- /dev/null
+++ b/validation/optim/shift-shift.c
@@ -0,0 +1,149 @@
+unsigned int shl0(unsigned int x)
+{
+	return x << 15 << 15;
+}
+
+unsigned int shl1(unsigned int x)
+{
+	return x << 16 << 15;
+}
+
+unsigned int shl2(unsigned int x)
+{
+	return x << 16 << 16;
+}
+
+unsigned int shl3(unsigned int x)
+{
+	return x << 12 << 10 << 10;
+}
+
+
+unsigned int lsr0(unsigned int x)
+{
+	return x >> 15 >> 15;
+}
+
+unsigned int lsr1(unsigned int x)
+{
+	return x >> 16 >> 15;
+}
+
+unsigned int lsr2(unsigned int x)
+{
+	return x >> 16 >> 16;
+}
+
+unsigned int lsr3(unsigned int x)
+{
+	return x >> 12 >> 10 >> 10;
+}
+
+
+int asr0(int x)
+{
+	return x >> 15 >> 15;
+}
+
+int asr1(int x)
+{
+	return x >> 16 >> 15;
+}
+
+int asr2(int x)
+{
+	return x >> 16 >> 16;
+}
+
+int asr3(int x)
+{
+	return x >> 12 >> 10 >> 10;
+}
+
+/*
+ * check-name: shift-shift
+ * check-command: test-linearize -Wno-decl $file
+ *
+ * check-output-start
+shl0:
+.L0:
+	<entry-point>
+	shl.32      %r3 <- %arg1, $30
+	ret.32      %r3
+
+
+shl1:
+.L2:
+	<entry-point>
+	shl.32      %r7 <- %arg1, $31
+	ret.32      %r7
+
+
+shl2:
+.L4:
+	<entry-point>
+	ret.32      $0
+
+
+shl3:
+.L6:
+	<entry-point>
+	ret.32      $0
+
+
+lsr0:
+.L8:
+	<entry-point>
+	lsr.32      %r20 <- %arg1, $30
+	ret.32      %r20
+
+
+lsr1:
+.L10:
+	<entry-point>
+	lsr.32      %r24 <- %arg1, $31
+	ret.32      %r24
+
+
+lsr2:
+.L12:
+	<entry-point>
+	ret.32      $0
+
+
+lsr3:
+.L14:
+	<entry-point>
+	ret.32      $0
+
+
+asr0:
+.L16:
+	<entry-point>
+	asr.32      %r37 <- %arg1, $30
+	ret.32      %r37
+
+
+asr1:
+.L18:
+	<entry-point>
+	asr.32      %r41 <- %arg1, $31
+	ret.32      %r41
+
+
+asr2:
+.L20:
+	<entry-point>
+	asr.32      %r45 <- %arg1, $31
+	ret.32      %r45
+
+
+asr3:
+.L22:
+	<entry-point>
+	asr.32      %r50 <- %arg1, $31
+	ret.32      %r50
+
+
+ * check-output-end
+ */