62 lines
2.0 KiB
LLVM
62 lines
2.0 KiB
LLVM
; If we have an 'and' of the result of an 'or', and one of the 'or' operands
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; cannot have contributed any of the resultant bits, delete the or. This
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; occurs for very common C/C++ code like this:
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;
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; struct foo { int A : 16; int B : 16; };
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; void test(struct foo *F, int X, int Y) {
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; F->A = X; F->B = Y;
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; }
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;
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; Which corresponds to test1.
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; RUN: opt < %s -instcombine -S | \
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; RUN: not grep "or "
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define i32 @test1(i32 %X, i32 %Y) {
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%A = and i32 %X, 7 ; <i32> [#uses=1]
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%B = and i32 %Y, 8 ; <i32> [#uses=1]
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%C = or i32 %A, %B ; <i32> [#uses=1]
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;; This cannot include any bits from %Y!
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%D = and i32 %C, 7 ; <i32> [#uses=1]
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ret i32 %D
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}
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define i32 @test2(i32 %X, i8 %Y) {
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%B = zext i8 %Y to i32 ; <i32> [#uses=1]
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%C = or i32 %X, %B ; <i32> [#uses=1]
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;; This cannot include any bits from %Y!
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%D = and i32 %C, 65536 ; <i32> [#uses=1]
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ret i32 %D
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}
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define i32 @test3(i32 %X, i32 %Y) {
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%B = shl i32 %Y, 1 ; <i32> [#uses=1]
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%C = or i32 %X, %B ; <i32> [#uses=1]
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;; This cannot include any bits from %Y!
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%D = and i32 %C, 1 ; <i32> [#uses=1]
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ret i32 %D
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}
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define i32 @test4(i32 %X, i32 %Y) {
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%B = lshr i32 %Y, 31 ; <i32> [#uses=1]
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%C = or i32 %X, %B ; <i32> [#uses=1]
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;; This cannot include any bits from %Y!
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%D = and i32 %C, 2 ; <i32> [#uses=1]
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ret i32 %D
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}
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define i32 @or_test1(i32 %X, i32 %Y) {
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%A = and i32 %X, 1 ; <i32> [#uses=1]
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;; This cannot include any bits from X!
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%B = or i32 %A, 1 ; <i32> [#uses=1]
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ret i32 %B
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}
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define i8 @or_test2(i8 %X, i8 %Y) {
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%A = shl i8 %X, 7 ; <i8> [#uses=1]
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;; This cannot include any bits from X!
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%B = or i8 %A, -128 ; <i8> [#uses=1]
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ret i8 %B
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}
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