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llvm-mirror/test/Transforms/InstCombine/redundant-left-shift-input-masking-variant-a.ll
Roman Lebedev 74ebe31eb0 [NFC][InstCombine] More tests for "Dropping pointless masking before left shift" (PR42563) 
While we already fold that pattern if the sum of shift amounts is not
smaller than bitwidth, there's painfully obvious generalization:
  https://rise4fun.com/Alive/F5R
I.e. the "sub of shift amounts" tells us how many bits will be left
in the output. If it's less than bitwidth, we simply need to
apply a mask, which is constant.

llvm-svn: 372170
2019-09-17 19:32:11 +00:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt %s -instcombine -S | FileCheck %s
; If we have some pattern that leaves only some low bits set, and then performs
; left-shift of those bits, if none of the bits that are left after the final
; shift are modified by the mask, we can omit the mask.
; There are many variants to this pattern:
; a) (x & ((1 << maskNbits) - 1)) << shiftNbits
; simplify to:
; x << shiftNbits
; iff (maskNbits+shiftNbits) u>= bitwidth(x)
; Simple tests. We don't care about extra uses.
declare void @use32(i32)
define i32 @t0_basic(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t0_basic(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl i32 %t2, %t3
ret i32 %t4
}
define i32 @t1_bigger_shift(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t1_bigger_shift(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 33, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 33, %nbits ; subtracting from bitwidth+1
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl i32 %t2, %t3
ret i32 %t4
}
define i32 @t2_bigger_mask(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t2_bigger_mask(
; CHECK-NEXT: [[T0:%.*]] = add i32 [[NBITS:%.*]], 1
; CHECK-NEXT: [[T1:%.*]] = shl i32 1, [[T0]]
; CHECK-NEXT: [[T2:%.*]] = add nsw i32 [[T1]], -1
; CHECK-NEXT: [[T3:%.*]] = and i32 [[T2]], [[X:%.*]]
; CHECK-NEXT: [[T4:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: call void @use32(i32 [[T4]])
; CHECK-NEXT: [[T5:%.*]] = shl i32 [[X]], [[T4]]
; CHECK-NEXT: ret i32 [[T5]]
;
%t0 = add i32 %nbits, 1
%t1 = shl i32 1, %t0 ; shifting by nbits+1
%t2 = add nsw i32 %t1, -1
%t3 = and i32 %t2, %x
%t4 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
call void @use32(i32 %t4)
%t5 = shl i32 %t3, %t4
ret i32 %t5
}
; Vectors
declare void @use3xi32(<3 x i32>)
define <3 x i32> @t3_vec_splat(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t3_vec_splat(
; CHECK-NEXT: [[T1:%.*]] = shl <3 x i32> <i32 1, i32 1, i32 1>, [[NBITS:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add nsw <3 x i32> [[T1]], <i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[T3:%.*]] = and <3 x i32> [[T2]], [[X:%.*]]
; CHECK-NEXT: [[T4:%.*]] = sub <3 x i32> <i32 32, i32 32, i32 32>, [[NBITS]]
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[NBITS]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T1]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T2]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T3]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T4]])
; CHECK-NEXT: [[T5:%.*]] = shl <3 x i32> [[X]], [[T4]]
; CHECK-NEXT: ret <3 x i32> [[T5]]
;
%t0 = add <3 x i32> %nbits, <i32 0, i32 0, i32 0>
%t1 = shl <3 x i32> <i32 1, i32 1, i32 1>, %t0
%t2 = add nsw <3 x i32> %t1, <i32 -1, i32 -1, i32 -1>
%t3 = and <3 x i32> %t2, %x
%t4 = sub <3 x i32> <i32 32, i32 32, i32 32>, %nbits
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
call void @use3xi32(<3 x i32> %t3)
call void @use3xi32(<3 x i32> %t4)
%t5 = shl <3 x i32> %t3, %t4
ret <3 x i32> %t5
}
define <3 x i32> @t4_vec_nonsplat(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t4_vec_nonsplat(
; CHECK-NEXT: [[T0:%.*]] = add <3 x i32> [[NBITS:%.*]], <i32 -1, i32 0, i32 1>
; CHECK-NEXT: [[T1:%.*]] = shl <3 x i32> <i32 1, i32 1, i32 1>, [[T0]]
; CHECK-NEXT: [[T2:%.*]] = add nsw <3 x i32> [[T1]], <i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[T3:%.*]] = and <3 x i32> [[T2]], [[X:%.*]]
; CHECK-NEXT: [[T4:%.*]] = sub <3 x i32> <i32 33, i32 32, i32 32>, [[NBITS]]
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T0]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T1]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T2]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T3]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T4]])
; CHECK-NEXT: [[T5:%.*]] = shl <3 x i32> [[X]], [[T4]]
; CHECK-NEXT: ret <3 x i32> [[T5]]
;
%t0 = add <3 x i32> %nbits, <i32 -1, i32 0, i32 1>
%t1 = shl <3 x i32> <i32 1, i32 1, i32 1>, %t0
%t2 = add nsw <3 x i32> %t1, <i32 -1, i32 -1, i32 -1>
%t3 = and <3 x i32> %t2, %x
%t4 = sub <3 x i32> <i32 33, i32 32, i32 32>, %nbits
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
call void @use3xi32(<3 x i32> %t3)
call void @use3xi32(<3 x i32> %t4)
%t5 = shl <3 x i32> %t3, %t4
ret <3 x i32> %t5
}
define <3 x i32> @t5_vec_undef(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t5_vec_undef(
; CHECK-NEXT: [[T1:%.*]] = shl <3 x i32> <i32 1, i32 undef, i32 1>, [[NBITS:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add nsw <3 x i32> [[T1]], <i32 -1, i32 undef, i32 -1>
; CHECK-NEXT: [[T3:%.*]] = and <3 x i32> [[T2]], [[X:%.*]]
; CHECK-NEXT: [[T4:%.*]] = sub <3 x i32> <i32 32, i32 undef, i32 32>, [[NBITS]]
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[NBITS]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T1]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T2]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T3]])
; CHECK-NEXT: call void @use3xi32(<3 x i32> [[T4]])
; CHECK-NEXT: [[T5:%.*]] = shl <3 x i32> [[X]], [[T4]]
; CHECK-NEXT: ret <3 x i32> [[T5]]
;
%t0 = add <3 x i32> %nbits, <i32 0, i32 undef, i32 0>
%t1 = shl <3 x i32> <i32 1, i32 undef, i32 1>, %t0
%t2 = add nsw <3 x i32> %t1, <i32 -1, i32 undef, i32 -1>
%t3 = and <3 x i32> %t2, %x
%t4 = sub <3 x i32> <i32 32, i32 undef, i32 32>, %nbits
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
call void @use3xi32(<3 x i32> %t3)
call void @use3xi32(<3 x i32> %t4)
%t5 = shl <3 x i32> %t3, %t4
ret <3 x i32> %t5
}
; Commutativity
declare i32 @gen32()
define i32 @t6_commutativity0(i32 %nbits) {
; CHECK-LABEL: @t6_commutativity0(
; CHECK-NEXT: [[X:%.*]] = call i32 @gen32()
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[X]], [[T1]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%x = call i32 @gen32()
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %x, %t1 ; swapped
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl i32 %t2, %t3
ret i32 %t4
}
define i32 @t7_commutativity1(i32 %nbits0, i32 %nbits1) {
; CHECK-LABEL: @t7_commutativity1(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS0:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = shl i32 1, [[NBITS1:%.*]]
; CHECK-NEXT: [[T3:%.*]] = add nsw i32 [[T2]], -1
; CHECK-NEXT: [[T4:%.*]] = and i32 [[T3]], [[T1]]
; CHECK-NEXT: [[T5:%.*]] = sub i32 32, [[NBITS0]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: call void @use32(i32 [[T4]])
; CHECK-NEXT: call void @use32(i32 [[T5]])
; CHECK-NEXT: [[T6:%.*]] = shl i32 [[T4]], [[T5]]
; CHECK-NEXT: ret i32 [[T6]]
;
%t0 = shl i32 1, %nbits0
%t1 = add nsw i32 %t0, -1
%t2 = shl i32 1, %nbits1
%t3 = add nsw i32 %t2, -1
%t4 = and i32 %t3, %t1 ; both hands of 'and' could be mask..
%t5 = sub i32 32, %nbits0
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
call void @use32(i32 %t4)
call void @use32(i32 %t5)
%t6 = shl i32 %t4, %t5
ret i32 %t6
}
define i32 @t8_commutativity2(i32 %nbits0, i32 %nbits1) {
; CHECK-LABEL: @t8_commutativity2(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS0:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = shl i32 1, [[NBITS1:%.*]]
; CHECK-NEXT: [[T3:%.*]] = add nsw i32 [[T2]], -1
; CHECK-NEXT: [[T4:%.*]] = and i32 [[T3]], [[T1]]
; CHECK-NEXT: [[T5:%.*]] = sub i32 32, [[NBITS1]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: call void @use32(i32 [[T4]])
; CHECK-NEXT: call void @use32(i32 [[T5]])
; CHECK-NEXT: [[T6:%.*]] = shl i32 [[T1]], [[T5]]
; CHECK-NEXT: ret i32 [[T6]]
;
%t0 = shl i32 1, %nbits0
%t1 = add nsw i32 %t0, -1
%t2 = shl i32 1, %nbits1
%t3 = add nsw i32 %t2, -1
%t4 = and i32 %t3, %t1 ; both hands of 'and' could be mask..
%t5 = sub i32 32, %nbits1
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
call void @use32(i32 %t4)
call void @use32(i32 %t5)
%t6 = shl i32 %t4, %t5
ret i32 %t6
}
; Fast-math flags. We must not preserve them!
define i32 @t9_nuw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t9_nuw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl nuw i32 %t2, %t3
ret i32 %t4
}
define i32 @t10_nsw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t10_nsw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl nsw i32 %t2, %t3
ret i32 %t4
}
define i32 @t11_nuw_nsw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t11_nuw_nsw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[X]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl nuw nsw i32 %t2, %t3
ret i32 %t4
}
; Negative tests
define i32 @n12_not_minus_one(i32 %x, i32 %nbits) {
; CHECK-LABEL: @n12_not_minus_one(
; CHECK-NEXT: [[T0:%.*]] = shl i32 2, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], -1
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[T2]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 2, %nbits ; shifting not '-1'
%t1 = add nsw i32 %t0, -1
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl i32 %t2, %t3
ret i32 %t4
}
define i32 @n13_not_minus_one(i32 %x, i32 %nbits) {
; CHECK-LABEL: @n13_not_minus_one(
; CHECK-NEXT: [[T0:%.*]] = shl i32 1, [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = add nsw i32 [[T0]], 2147483647
; CHECK-NEXT: [[T2:%.*]] = and i32 [[T1]], [[X:%.*]]
; CHECK-NEXT: [[T3:%.*]] = sub i32 32, [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: call void @use32(i32 [[T3]])
; CHECK-NEXT: [[T4:%.*]] = shl i32 [[T2]], [[T3]]
; CHECK-NEXT: ret i32 [[T4]]
;
%t0 = shl i32 1, %nbits
%t1 = add nsw i32 %t0, 2147483647 ; adding not '-1'
%t2 = and i32 %t1, %x
%t3 = sub i32 32, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
call void @use32(i32 %t3)
%t4 = shl i32 %t2, %t3
ret i32 %t4
}
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