1 files changed, 277 insertions, 0 deletions
diff --git a/llvm/test/Transforms/InstCombine/redundant-left-shift-input-masking-variant-c.ll b/llvm/test/Transforms/InstCombine/redundant-left-shift-input-masking-variant-c.ll
new file mode 100644
index 00000000000..cf47d96ca2b
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/redundant-left-shift-input-masking-variant-c.ll
@@ -0,0 +1,277 @@
+; 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:
+;   c)  (x & (-1 >> 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:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  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:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; 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 [[T1]], [[T2]]
+; CHECK-NEXT:    ret i32 [[T3]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  %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:%.*]] = lshr <3 x i32> <i32 -1, i32 -1, i32 -1>, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and <3 x i32> [[T0]], [[X:%.*]]
+; 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> [[T1]], [[T2]]
+; CHECK-NEXT:    ret <3 x i32> [[T3]]
+;
+  %t0 = lshr <3 x i32> <i32 -1, i32 -1, i32 -1>, %nbits
+  %t1 = and <3 x i32> %t0, %x
+  %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:%.*]] = lshr <3 x i32> <i32 -1, i32 -1, i32 -1>, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and <3 x i32> [[T0]], [[X:%.*]]
+; 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> [[T1]], [[T2]]
+; CHECK-NEXT:    ret <3 x i32> [[T3]]
+;
+  %t0 = lshr <3 x i32> <i32 -1, i32 -1, i32 -1>, %nbits
+  %t1 = and <3 x i32> %t0, %x
+  %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:%.*]] = lshr <3 x i32> <i32 -1, i32 undef, i32 -1>, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and <3 x i32> [[T0]], [[X:%.*]]
+; 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> [[T1]], [[T2]]
+; CHECK-NEXT:    ret <3 x i32> [[T3]]
+;
+  %t0 = lshr <3 x i32> <i32 -1, i32 undef, i32 -1>, %nbits
+  %t1 = and <3 x i32> %t0, %x
+  %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
+}
+
+; Commutativity
+
+declare i32 @gen32()
+
+define i32 @t5_commutativity0(i32 %nbits) {
+; CHECK-LABEL: @t5_commutativity0(
+; CHECK-NEXT:    [[X:%.*]] = call i32 @gen32()
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[X]], [[T0]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %x = call i32 @gen32()
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %x, %t0 ; swapped
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  %t2 = shl i32 %t1, %nbits
+  ret i32 %t2
+}
+
+define i32 @t6_commutativity1(i32 %nbits0, i32 %nbits1) {
+; CHECK-LABEL: @t6_commutativity1(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS0:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = lshr i32 -1, [[NBITS1:%.*]]
+; CHECK-NEXT:    [[T2:%.*]] = and i32 [[T0]], [[T1]]
+; 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 [[T2]], [[NBITS0]]
+; CHECK-NEXT:    ret i32 [[T3]]
+;
+  %t0 = lshr i32 -1, %nbits0
+  %t1 = lshr i32 -1, %nbits1
+  %t2 = and i32 %t0, %t1 ; both hands of 'and' could be mask..
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  call void @use32(i32 %t2)
+  %t3 = shl i32 %t2, %nbits0
+  ret i32 %t3
+}
+define i32 @t7_commutativity2(i32 %nbits0, i32 %nbits1) {
+; CHECK-LABEL: @t7_commutativity2(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS0:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = lshr i32 -1, [[NBITS1:%.*]]
+; CHECK-NEXT:    [[T2:%.*]] = and i32 [[T0]], [[T1]]
+; 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 [[T2]], [[NBITS1]]
+; CHECK-NEXT:    ret i32 [[T3]]
+;
+  %t0 = lshr i32 -1, %nbits0
+  %t1 = lshr i32 -1, %nbits1
+  %t2 = and i32 %t0, %t1 ; both hands of 'and' could be mask..
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  call void @use32(i32 %t2)
+  %t3 = shl i32 %t2, %nbits1
+  ret i32 %t3
+}
+
+; Fast-math flags. We must not preserve them!
+
+define i32 @t8_nuw(i32 %x, i32 %nbits) {
+; CHECK-LABEL: @t8_nuw(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl nuw i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  %t2 = shl nuw i32 %t1, %nbits
+  ret i32 %t2
+}
+
+define i32 @t9_nsw(i32 %x, i32 %nbits) {
+; CHECK-LABEL: @t9_nsw(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl nsw i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  %t2 = shl nsw i32 %t1, %nbits
+  ret i32 %t2
+}
+
+define i32 @t10_nuw_nsw(i32 %x, i32 %nbits) {
+; CHECK-LABEL: @t10_nuw_nsw(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl nuw nsw i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  %t2 = shl nuw nsw i32 %t1, %nbits
+  ret i32 %t2
+}
+
+; Negative tests
+
+define i32 @n11(i32 %x, i32 %nbits) {
+; CHECK-LABEL: @n11(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -2, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[T0]])
+; CHECK-NEXT:    call void @use32(i32 [[T1]])
+; CHECK-NEXT:    [[T2:%.*]] = shl i32 [[T1]], [[NBITS]]
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -2, %nbits ; shifting not '-1'
+  %t1 = and i32 %t0, %x
+  call void @use32(i32 %t0)
+  call void @use32(i32 %t1)
+  %t2 = shl i32 %t1, %nbits
+  ret i32 %t2
+}
+
+define i32 @n12(i32 %x, i32 %nbits) {
+; CHECK-LABEL: @n12(
+; CHECK-NEXT:    [[T0:%.*]] = lshr i32 -1, [[NBITS:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = and i32 [[T0]], [[X:%.*]]
+; 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:    ret i32 [[T2]]
+;
+  %t0 = lshr i32 -1, %nbits
+  %t1 = and i32 %t0, %x
+  %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 ; shift is smaller than mask
+  ret i32 %t2
+}