tests/misc: Add a test for a load that hits two preceding stores

This checks that the store forwarding machinery in the dcache
correctly combines forwarded stores when they are partial stores
(i.e. only writing part of the doubleword, as for a byte store).

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

tests/misc/head.S

@@ -162,3 +162,26 @@ test_bdnzl:
 	li	%r3,0
 9:	mtlr	%r10
 	blr
+
+/* Test that a load that hits stores gets the correct data */
+	.global test_loadhitstore
+test_loadhitstore:
+	addi	%r5,%r1,-16
+	ld	%r0,0(%r5)
+	li	%r0,0
+	std	%r0,0(%r5)
+	li	%r6,0x66
+	li	%r7,0x77
+	.balign	64
+	nop
+	nop
+	nop
+	nop
+	stb	%r6,2(%r5)
+	stb	%r7,3(%r5)
+	ld	%r0,0(%r5)
+	sldi	%r6,%r6,16
+	sldi	%r7,%r7,24
+	or	%r7,%r6,%r7
+	subf	%r3,%r0,%r7
+	blr

tests/misc/misc.c

@@ -15,6 +15,7 @@ extern long test_addpcis_2(void);
 extern long test_mfpvr(void);
 extern long test_mtpvr(void);
 extern long test_bdnzl(void);
+extern long test_loadhitstore(void);
 
 // i < 100
 void print_test_number(int i)
@@ -66,5 +67,12 @@ int main(void)
 	} else
 		puts(PASS);
 
+	print_test_number(6);
+	if (test_loadhitstore() != 0) {
+		fail = 1;
+		puts(FAIL);
+	} else
+		puts(PASS);
+
 	return fail;
 }

tests/test_misc.console_out

@@ -3,3 +3,4 @@ Test 02:PASS
 Test 03:PASS
 Test 04:PASS
 Test 05:PASS
+Test 06:PASS