1 ; If we have an 'and' of the result of an 'or', and one of the 'or' operands 2 ; cannot have contributed any of the resultant bits, delete the or. This 3 ; occurs for very common C/C++ code like this: 4 ; 5 ; struct foo { int A : 16; int B : 16; }; 6 ; void test(struct foo *F, int X, int Y) { 7 ; F->A = X; F->B = Y; 8 ; } 9 ; 10 ; Which corresponds to test1. 11 12 ; RUN: opt < %s -instcombine -S | \ 13 ; RUN: not grep "or " 14 15 define i32 @test1(i32 %X, i32 %Y) { 16 %A = and i32 %X, 7 ; <i32> [#uses=1] 17 %B = and i32 %Y, 8 ; <i32> [#uses=1] 18 %C = or i32 %A, %B ; <i32> [#uses=1] 19 ;; This cannot include any bits from %Y! 20 %D = and i32 %C, 7 ; <i32> [#uses=1] 21 ret i32 %D 22 } 23 24 define i32 @test2(i32 %X, i8 %Y) { 25 %B = zext i8 %Y to i32 ; <i32> [#uses=1] 26 %C = or i32 %X, %B ; <i32> [#uses=1] 27 ;; This cannot include any bits from %Y! 28 %D = and i32 %C, 65536 ; <i32> [#uses=1] 29 ret i32 %D 30 } 31 32 define i32 @test3(i32 %X, i32 %Y) { 33 %B = shl i32 %Y, 1 ; <i32> [#uses=1] 34 %C = or i32 %X, %B ; <i32> [#uses=1] 35 ;; This cannot include any bits from %Y! 36 %D = and i32 %C, 1 ; <i32> [#uses=1] 37 ret i32 %D 38 } 39 40 define i32 @test4(i32 %X, i32 %Y) { 41 %B = lshr i32 %Y, 31 ; <i32> [#uses=1] 42 %C = or i32 %X, %B ; <i32> [#uses=1] 43 ;; This cannot include any bits from %Y! 44 %D = and i32 %C, 2 ; <i32> [#uses=1] 45 ret i32 %D 46 } 47 48 define i32 @or_test1(i32 %X, i32 %Y) { 49 %A = and i32 %X, 1 ; <i32> [#uses=1] 50 ;; This cannot include any bits from X! 51 %B = or i32 %A, 1 ; <i32> [#uses=1] 52 ret i32 %B 53 } 54 55 define i8 @or_test2(i8 %X, i8 %Y) { 56 %A = shl i8 %X, 7 ; <i8> [#uses=1] 57 ;; This cannot include any bits from X! 58 %B = or i8 %A, -128 ; <i8> [#uses=1] 59 ret i8 %B 60 } 61 62
