New testcase for common bitfield manipulation instruction sequences.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19218 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/Transforms/InstCombine/and-or-and.ll b/test/Transforms/InstCombine/and-or-and.ll
new file mode 100644 (file)
index 0000000..f497f3f
--- /dev/null
+++ b/test/Transforms/InstCombine/and-or-and.ll
@@ -0,0 +1,54 @@
+; If we have an 'and' of the result of an 'or', and one of the 'or' operands
+; cannot have contributed any of the resultant bits, delete the or.  This
+; occurs for very common C/C++ code like this:
+;
+; struct foo { int A : 16; int B : 16; };
+; void test(struct foo *F, int X, int Y) {
+;        F->A = X; F->B = Y;
+; }
+;
+; Which corresponds to test1.
+
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep 'or '
+
+int %test1(int %X, int %Y) {
+       %A = and int %X, 7
+       %B = and int %Y, 8
+       %C = or int %A, %B
+       %D = and int %C, 7  ;; This cannot include any bits from %Y!
+       ret int %D
+}
+
+int %test2(int %X, ubyte %Y) {
+       %B = cast ubyte %Y to int
+       %C = or int %X, %B
+       %D = and int %C, 65536  ;; This cannot include any bits from %Y!
+       ret int %D
+}
+
+int %test3(int %X, int %Y) {
+       %B = shl int %Y, ubyte 1
+       %C = or int %X, %B
+       %D = and int %C, 1  ;; This cannot include any bits from %Y!
+       ret int %D
+}
+
+uint %test4(uint %X, uint %Y) {
+       %B = shr uint %Y, ubyte 31
+       %C = or uint %X, %B
+       %D = and uint %C, 2  ;; This cannot include any bits from %Y!
+       ret uint %D
+}
+
+int %or_test1(int %X, int %Y) {
+       %A = and int %X, 1
+       %B = or int %A, 1     ;; This cannot include any bits from X!
+       ret int %B
+}
+
+ubyte %or_test2(ubyte %X, ubyte %Y) {
+       %A = shl ubyte %X, ubyte 7
+       %B = or ubyte %A, 128     ;; This cannot include any bits from X!
+       ret ubyte %B
+}
+