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1; If we have an 'and' of the result of an 'or', and one of the 'or' operands2; cannot have contributed any of the resultant bits, delete the or. This3; 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 -passes=instcombine -S | \13; RUN: not grep "or "14 15define 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 %D22}23 24define 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 %D30}31 32define 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 %D38}39 40define 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 %D46}47 48define 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 %B53}54 55define 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 %B60}61 62