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[InstCombine] Add test case demonstrating missed opportunities for removing add/sub when the LSBs of one input are known to be 0 and MSBs of the output aren't consumed. 

llvm-svn: 299263
This commit is contained in:
Craig Topper 2017-03-31 21:08:37 +00:00
parent d04c9b999c
commit 0d8801f991
1 changed files with 63 additions and 0 deletions
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63
llvm/test/Transforms/InstCombine/and2.ll
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@ -122,3 +122,66 @@ define i64 @test10(i64 %x) {
ret i64 %add
}
; The add in this test is unnecessary because the LSBs of the RHS are 0 and we only consume those bits.
define i32 @test11(i32 %a, i32 %b) {
; CHECK-LABEL: @test11(
; CHECK-NEXT: [[X:%.*]] = shl i32 [[A:%.*]], 8
; CHECK-NEXT: [[Y:%.*]] = add i32 [[X]], [[B:%.*]]
; CHECK-NEXT: [[Z:%.*]] = and i32 [[Y]], 128
; CHECK-NEXT: [[W:%.*]] = mul i32 [[Z]], [[X]]
; CHECK-NEXT: ret i32 [[W]]
;
%x = shl i32 %a, 8
%y = add i32 %x, %b
%z = and i32 %y, 128
%w = mul i32 %z, %x ; to keep the shift from being removed
ret i32 %w
}
; The add in this test is unnecessary because the LSBs of the RHS are 0 and we only consume those bits.
define i32 @test12(i32 %a, i32 %b) {
; CHECK-LABEL: @test12(
; CHECK-NEXT: [[X:%.*]] = shl i32 [[A:%.*]], 8
; CHECK-NEXT: [[Y:%.*]] = add i32 [[X]], [[B:%.*]]
; CHECK-NEXT: [[Z:%.*]] = and i32 [[Y]], 128
; CHECK-NEXT: [[W:%.*]] = mul i32 [[Z]], [[X]]
; CHECK-NEXT: ret i32 [[W]]
;
%x = shl i32 %a, 8
%y = add i32 %b, %x
%z = and i32 %y, 128
%w = mul i32 %z, %x ; to keep the shift from being removed
ret i32 %w
}
; The sub in this test is unnecessary because the LSBs of the RHS are 0 and we only consume those bits.
define i32 @test13(i32 %a, i32 %b) {
; CHECK-LABEL: @test13(
; CHECK-NEXT: [[X:%.*]] = shl i32 [[A:%.*]], 8
; CHECK-NEXT: [[Y:%.*]] = sub i32 [[B:%.*]], [[X]]
; CHECK-NEXT: [[Z:%.*]] = and i32 [[Y]], 128
; CHECK-NEXT: [[W:%.*]] = mul i32 [[Z]], [[X]]
; CHECK-NEXT: ret i32 [[W]]
;
%x = shl i32 %a, 8
%y = sub i32 %b, %x
%z = and i32 %y, 128
%w = mul i32 %z, %x ; to keep the shift from being removed
ret i32 %w
}
; The sub in this test cannot be removed because we need to keep the negation of %b
define i32 @test14(i32 %a, i32 %b) {
; CHECK-LABEL: @test14(
; CHECK-NEXT: [[X:%.*]] = shl i32 [[A:%.*]], 8
; CHECK-NEXT: [[Y:%.*]] = sub i32 [[X]], [[B:%.*]]
; CHECK-NEXT: [[Z:%.*]] = and i32 [[Y]], 128
; CHECK-NEXT: [[W:%.*]] = mul i32 [[Z]], [[X]]
; CHECK-NEXT: ret i32 [[W]]
;
%x = shl i32 %a, 8
%y = sub i32 %x, %b
%z = and i32 %y, 128
%w = mul i32 %z, %x ; to keep the shift from being removed
ret i32 %w
}