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When canonicalizing dags according to the rule (shl (zext (shr X, c1) ), c1) ==> (zext (shl (shr X, c1), c1)) remember to add the new shl dag to the DAGCombiner worklist of nodes. If we don't explicitly add it to the worklist of nodes to visit, we may not trigger later on the rule that folds the shift left + logical shift right into a AND instruction with bitmask. llvm-svn: 192883
210 lines
4.0 KiB
LLVM
210 lines
4.0 KiB
LLVM
; RUN: llc < %s -mtriple=x86_64-linux-gnu | FileCheck %s
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; fold (shl (zext (lshr (A, X))), X) -> (zext (shl (lshr (A, X)), X))
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; Canolicalize the sequence shl/zext/lshr performing the zeroextend
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; as the last instruction of the sequence.
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; This will help DAGCombiner to identify and then fold the sequence
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; of shifts into a single AND.
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; This transformation is profitable if the shift amounts are the same
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; and if there is only one use of the zext.
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define i16 @fun1(i8 zeroext %v) {
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entry:
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%shr = lshr i8 %v, 4
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%ext = zext i8 %shr to i16
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%shl = shl i16 %ext, 4
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ret i16 %shl
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}
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; CHECK-LABEL: @fun1
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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define i32 @fun2(i8 zeroext %v) {
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entry:
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%shr = lshr i8 %v, 4
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%ext = zext i8 %shr to i32
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%shl = shl i32 %ext, 4
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ret i32 %shl
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}
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; CHECK-LABEL: @fun2
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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define i32 @fun3(i16 zeroext %v) {
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entry:
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%shr = lshr i16 %v, 4
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%ext = zext i16 %shr to i32
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%shl = shl i32 %ext, 4
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ret i32 %shl
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}
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; CHECK-LABEL: @fun3
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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define i64 @fun4(i8 zeroext %v) {
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entry:
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%shr = lshr i8 %v, 4
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%ext = zext i8 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun4
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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define i64 @fun5(i16 zeroext %v) {
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entry:
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%shr = lshr i16 %v, 4
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%ext = zext i16 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun5
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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define i64 @fun6(i32 zeroext %v) {
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entry:
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%shr = lshr i32 %v, 4
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%ext = zext i32 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun6
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; CHECK: and
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: ret
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; Don't fold the pattern if we use arithmetic shifts.
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define i64 @fun7(i8 zeroext %v) {
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entry:
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%shr = ashr i8 %v, 4
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%ext = zext i8 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun7
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; CHECK: sar
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; CHECK: shl
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; CHECK: ret
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define i64 @fun8(i16 zeroext %v) {
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entry:
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%shr = ashr i16 %v, 4
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%ext = zext i16 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun8
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; CHECK: sar
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; CHECK: shl
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; CHECK: ret
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define i64 @fun9(i32 zeroext %v) {
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entry:
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%shr = ashr i32 %v, 4
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%ext = zext i32 %shr to i64
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%shl = shl i64 %ext, 4
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ret i64 %shl
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}
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; CHECK-LABEL: @fun9
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; CHECK: sar
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; CHECK: shl
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; CHECK: ret
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; Don't fold the pattern if there is more than one use of the
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; operand in input to the shift left.
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define i64 @fun10(i8 zeroext %v) {
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entry:
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%shr = lshr i8 %v, 4
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%ext = zext i8 %shr to i64
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%shl = shl i64 %ext, 4
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%add = add i64 %shl, %ext
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ret i64 %add
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}
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; CHECK-LABEL: @fun10
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; CHECK: shr
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; CHECK: shl
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; CHECK: ret
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define i64 @fun11(i16 zeroext %v) {
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entry:
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%shr = lshr i16 %v, 4
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%ext = zext i16 %shr to i64
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%shl = shl i64 %ext, 4
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%add = add i64 %shl, %ext
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ret i64 %add
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}
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; CHECK-LABEL: @fun11
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; CHECK: shr
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; CHECK: shl
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; CHECK: ret
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define i64 @fun12(i32 zeroext %v) {
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entry:
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%shr = lshr i32 %v, 4
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%ext = zext i32 %shr to i64
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%shl = shl i64 %ext, 4
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%add = add i64 %shl, %ext
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ret i64 %add
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}
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; CHECK-LABEL: @fun12
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; CHECK: shr
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; CHECK: shl
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; CHECK: ret
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; PR17380
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; Make sure that the combined dags are legal if we run the DAGCombiner after
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; Legalization took place. The add instruction is redundant and increases by
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; one the number of uses of the zext. This prevents the transformation from
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; firing before dags are legalized and optimized.
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; Once the add is removed, the number of uses becomes one and therefore the
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; dags are canonicalized. After Legalization, we need to make sure that the
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; valuetype for the shift count is legal.
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; Verify also that we correctly fold the shl-shr sequence into an
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; AND with bitmask.
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define void @g(i32 %a) {
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%b = lshr i32 %a, 2
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%c = zext i32 %b to i64
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%d = add i64 %c, 1
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%e = shl i64 %c, 2
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tail call void @f(i64 %e)
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ret void
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}
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; CHECK-LABEL: @g
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; CHECK-NOT: shr
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; CHECK-NOT: shl
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; CHECK: and
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; CHECK-NEXT: jmp
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declare void @f(i64)
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