| ; 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 |
| } |
| |