; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=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:
; e) ((x << maskNbits) l>> maskNbits) << shiftNbits
; simplify to:
; x << shiftNbits
; iff (shiftNbits-maskNbits) s>= 0 (i.e. shiftNbits u>= maskNbits)
; 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 [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: ret i32 [[T0]]
;
%t0 = shl i32 %x, %nbits
%t1 = lshr i32 %t0, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl i32 %t1, %nbits
ret i32 %t2
}
define i32 @t1_bigger_shift(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t1_bigger_shift(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[NBITS]]
; CHECK-NEXT: [[T2:%.*]] = add i32 [[NBITS]], 1
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: call void @use32(i32 [[T2]])
; CHECK-NEXT: [[T3:%.*]] = shl i32 [[X]], [[T2]]
; CHECK-NEXT: ret i32 [[T3]]
;
%t0 = shl i32 %x, %nbits
%t1 = lshr i32 %t0, %nbits
%t2 = add i32 %nbits, 1
call void @use32(i32 %t0)
call void @use32(i32 %t1)
call void @use32(i32 %t2)
%t3 = shl i32 %t1, %t2
ret i32 %t3
}
; Vectors
declare void @use3xi32(<3 x i32>)
define <3 x i32> @t2_vec_splat(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t2_vec_splat(
; CHECK-NEXT: [[T0:%.*]] = shl <3 x i32> [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact <3 x i32> [[T0]], [[NBITS]]
; CHECK-NEXT: [[T2:%.*]] = add <3 x i32> [[NBITS]], <i32 1, i32 1, i32 1>
; 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: [[T3:%.*]] = shl <3 x i32> [[X]], [[T2]]
; CHECK-NEXT: ret <3 x i32> [[T3]]
;
%t0 = shl <3 x i32> %x, %nbits
%t1 = lshr <3 x i32> %t0, %nbits
%t2 = add <3 x i32> %nbits, <i32 1, i32 1, i32 1>
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
%t3 = shl <3 x i32> %t1, %t2
ret <3 x i32> %t3
}
define <3 x i32> @t3_vec_nonsplat(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t3_vec_nonsplat(
; CHECK-NEXT: [[T0:%.*]] = shl <3 x i32> [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact <3 x i32> [[T0]], [[NBITS]]
; CHECK-NEXT: [[T2:%.*]] = add <3 x i32> [[NBITS]], <i32 1, i32 0, i32 2>
; 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: [[T3:%.*]] = shl <3 x i32> [[X]], [[T2]]
; CHECK-NEXT: ret <3 x i32> [[T3]]
;
%t0 = shl <3 x i32> %x, %nbits
%t1 = lshr <3 x i32> %t0, %nbits
%t2 = add <3 x i32> %nbits, <i32 1, i32 0, i32 2>
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
%t3 = shl <3 x i32> %t1, %t2
ret <3 x i32> %t3
}
define <3 x i32> @t4_vec_undef(<3 x i32> %x, <3 x i32> %nbits) {
; CHECK-LABEL: @t4_vec_undef(
; CHECK-NEXT: [[T0:%.*]] = shl <3 x i32> [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact <3 x i32> [[T0]], [[NBITS]]
; CHECK-NEXT: [[T2:%.*]] = add <3 x i32> [[NBITS]], <i32 1, i32 undef, i32 1>
; 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: [[T3:%.*]] = shl <3 x i32> [[X]], [[T2]]
; CHECK-NEXT: ret <3 x i32> [[T3]]
;
%t0 = shl <3 x i32> %x, %nbits
%t1 = lshr <3 x i32> %t0, %nbits
%t2 = add <3 x i32> %nbits, <i32 1, i32 undef, i32 1>
call void @use3xi32(<3 x i32> %t0)
call void @use3xi32(<3 x i32> %t1)
call void @use3xi32(<3 x i32> %t2)
%t3 = shl <3 x i32> %t1, %t2
ret <3 x i32> %t3
}
; Fast-math flags. We must not preserve them!
define i32 @t5_nuw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t5_nuw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: ret i32 [[T0]]
;
%t0 = shl i32 %x, %nbits
%t1 = lshr i32 %t0, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl nuw i32 %t1, %nbits
ret i32 %t2
}
define i32 @t6_nsw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t6_nsw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: ret i32 [[T0]]
;
%t0 = shl i32 %x, %nbits
%t1 = lshr i32 %t0, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl nsw i32 %t1, %nbits
ret i32 %t2
}
define i32 @t7_nuw_nsw(i32 %x, i32 %nbits) {
; CHECK-LABEL: @t7_nuw_nsw(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[NBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: ret i32 [[T0]]
;
%t0 = shl i32 %x, %nbits
%t1 = lshr i32 %t0, %nbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl nuw nsw i32 %t1, %nbits
ret i32 %t2
}
; Special test
declare void @llvm.assume(i1 %cond)
; We can't simplify (%shiftnbits-%masknbits) but we have an assumption.
define i32 @t8_assume_uge(i32 %x, i32 %masknbits, i32 %shiftnbits) {
; CHECK-LABEL: @t8_assume_uge(
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 [[SHIFTNBITS:%.*]], [[MASKNBITS:%.*]]
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[MASKNBITS]]
; CHECK-NEXT: [[T1:%.*]] = lshr exact i32 [[T0]], [[MASKNBITS]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = shl i32 [[T1]], [[SHIFTNBITS]]
; CHECK-NEXT: ret i32 [[T2]]
;
%cmp = icmp uge i32 %shiftnbits, %masknbits
call void @llvm.assume(i1 %cmp)
%t0 = shl i32 %x, %masknbits
%t1 = lshr i32 %t0, %masknbits
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl i32 %t1, %shiftnbits
ret i32 %t2
}
; Negative tests
define i32 @n9_different_shamts0(i32 %x, i32 %nbits0, i32 %nbits1) {
; CHECK-LABEL: @n9_different_shamts0(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS0:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr i32 [[T0]], [[NBITS1:%.*]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = shl i32 [[T1]], [[NBITS0]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = shl i32 %x, %nbits0 ; different shift amts
%t1 = lshr i32 %t0, %nbits1 ; different shift amts
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl i32 %t1, %nbits0
ret i32 %t2
}
define i32 @n10_different_shamts1(i32 %x, i32 %nbits0, i32 %nbits1) {
; CHECK-LABEL: @n10_different_shamts1(
; CHECK-NEXT: [[T0:%.*]] = shl i32 [[X:%.*]], [[NBITS0:%.*]]
; CHECK-NEXT: [[T1:%.*]] = lshr i32 [[T0]], [[NBITS1:%.*]]
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = shl i32 [[T1]], [[NBITS1]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = shl i32 %x, %nbits0 ; different shift amts
%t1 = lshr i32 %t0, %nbits1 ; different shift amts
call void @use32(i32 %t0)
call void @use32(i32 %t1)
%t2 = shl i32 %t1, %nbits1
ret i32 %t2
}
Codebase Browser
llvm