[NFC][InstCombine] Tests for (x >> y) << y -> x & (-1 << y) fold.

We already do it for splat constants, but not just values.
Also, undef cases are mostly non-functional.

https://bugs.llvm.org/show_bug.cgi?id=37603
https://reviews.llvm.org/D46760#1123713
https://rise4fun.com/Alive/cplX

llvm-svn: 334347

1 files changed, 316 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll b/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll
new file mode 100644
index 00000000000..c6730aaa5e0
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll
@@ -0,0 +1,316 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; https://bugs.llvm.org/show_bug.cgi?id=37603
+; https://reviews.llvm.org/D46760#1123713
+
+; Pattern:
+;   x >> y << y
+; Should be transformed into:
+;   x & (-1 << y)
+
+; ============================================================================ ;
+; Basic positive tests
+; ============================================================================ ;
+
+define i32 @positive_samevar(i32 %x, i32 %y) {
+; CHECK-LABEL: @positive_samevar(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = shl i32 [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr i32 %x, %y
+  %ret = shl i32 %tmp0, %y
+  ret i32 %ret
+}
+
+define i32 @positive_sameconst(i32 %x) {
+; CHECK-LABEL: @positive_sameconst(
+; CHECK-NEXT:    [[TMP0:%.*]] = and i32 [[X:%.*]], -32
+; CHECK-NEXT:    ret i32 [[TMP0]]
+;
+  %tmp0 = lshr i32 %x, 5
+  %ret = shl i32 %tmp0, 5
+  ret i32 %ret
+}
+
+define i32 @positive_biggerlshr(i32 %x) {
+; CHECK-LABEL: @positive_biggerlshr(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr i32 [[X:%.*]], 10
+; CHECK-NEXT:    [[RET:%.*]] = shl nuw nsw i32 [[TMP0]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr i32 %x, 10
+  %ret = shl i32 %tmp0, 5
+  ret i32 %ret
+}
+
+define i32 @positive_biggershl(i32 %x) {
+; CHECK-LABEL: @positive_biggershl(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr i32 [[X:%.*]], 5
+; CHECK-NEXT:    [[RET:%.*]] = shl i32 [[TMP0]], 10
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr i32 %x, 5
+  %ret = shl i32 %tmp0, 10
+  ret i32 %ret
+}
+
+; ============================================================================ ;
+; EXACT on the first shift
+; ============================================================================ ;
+
+define i32 @positive_samevar_lshrexact(i32 %x, i32 %y) {
+; CHECK-LABEL: @positive_samevar_lshrexact(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %tmp0 = lshr exact i32 %x, %y
+  %ret = shl i32 %tmp0, %y ; this one is obviously 'nuw'.
+  ret i32 %ret
+}
+
+define i32 @positive_sameconst_lshrexact(i32 %x) {
+; CHECK-LABEL: @positive_sameconst_lshrexact(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %tmp0 = lshr exact i32 %x, 5
+  %ret = shl i32 %tmp0, 5 ; this one is obviously 'nuw'.
+  ret i32 %ret
+}
+
+define i32 @positive_biggerlshr_lshrexact(i32 %x) {
+; CHECK-LABEL: @positive_biggerlshr_lshrexact(
+; CHECK-NEXT:    [[RET:%.*]] = lshr exact i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr exact i32 %x, 10
+  %ret = shl i32 %tmp0, 5 ; this one is obviously 'nuw'.
+  ret i32 %ret
+}
+
+define i32 @positive_biggershl_lshrexact(i32 %x) {
+; CHECK-LABEL: @positive_biggershl_lshrexact(
+; CHECK-NEXT:    [[RET:%.*]] = shl i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr exact i32 %x, 5
+  %ret = shl i32 %tmp0, 10
+  ret i32 %ret
+}
+
+define i32 @positive_biggershl_lshrexact_shlexact(i32 %x) {
+; CHECK-LABEL: @positive_biggershl_lshrexact_shlexact(
+; CHECK-NEXT:    [[RET:%.*]] = shl nuw i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr exact i32 %x, 5
+  %ret = shl nuw i32 %tmp0, 10
+  ret i32 %ret
+}
+
+; ============================================================================ ;
+; Vector
+; ============================================================================ ;
+
+define <2 x i32> @positive_samevar_vec(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @positive_samevar_vec(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = shl <2 x i32> [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = lshr <2 x i32> %x, %y
+  %ret = shl <2 x i32> %tmp0, %y
+  ret <2 x i32> %ret
+}
+
+; ============================================================================ ;
+; Constant Vectors
+; ============================================================================ ;
+
+define <2 x i32> @positive_sameconst_vec(<2 x i32> %x) {
+; CHECK-LABEL: @positive_sameconst_vec(
+; CHECK-NEXT:    [[TMP0:%.*]] = and <2 x i32> [[X:%.*]], <i32 -32, i32 -32>
+; CHECK-NEXT:    ret <2 x i32> [[TMP0]]
+;
+  %tmp0 = lshr <2 x i32> %x, <i32 5, i32 5>
+  %ret = shl <2 x i32> %tmp0, <i32 5, i32 5>
+  ret <2 x i32> %ret
+}
+
+define <3 x i32> @positive_sameconst_vec_undef0(<3 x i32> %x) {
+; CHECK-LABEL: @positive_sameconst_vec_undef0(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 5, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_sameconst_vec_undef1(<3 x i32> %x) {
+; CHECK-LABEL: @positive_sameconst_vec_undef1(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 5, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 undef, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_sameconst_vec_undef2(<3 x i32> %x) {
+; CHECK-LABEL: @positive_sameconst_vec_undef2(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 undef, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <2 x i32> @positive_biggerlshr_vec(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggerlshr_vec(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <2 x i32> [[X:%.*]], <i32 10, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = shl nuw nsw <2 x i32> [[TMP0]], <i32 5, i32 5>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = lshr <2 x i32> %x, <i32 10, i32 10>
+  %ret = shl <2 x i32> %tmp0, <i32 5, i32 5>
+  ret <2 x i32> %ret
+}
+
+define <3 x i32> @positive_biggerlshr_vec_undef0(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggerlshr_vec_undef0(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 10, i32 undef, i32 10>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 5, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_biggerlshr_vec_undef1(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggerlshr_vec_undef1(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 10, i32 10, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 10, i32 10, i32 10>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 undef, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_biggerlshr_vec_undef2(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggerlshr_vec_undef2(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 10, i32 undef, i32 10>
+  %ret = shl <3 x i32> %tmp0, <i32 5, i32 undef, i32 5>
+  ret <3 x i32> %ret
+}
+
+define <2 x i32> @positive_biggershl_vec(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggershl_vec(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <2 x i32> [[X:%.*]], <i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <2 x i32> [[TMP0]], <i32 10, i32 10>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = lshr <2 x i32> %x, <i32 5, i32 5>
+  %ret = shl <2 x i32> %tmp0, <i32 10, i32 10>
+  ret <2 x i32> %ret
+}
+
+define <3 x i32> @positive_biggershl_vec_undef0(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggershl_vec_undef0(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 10, i32 10, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 10, i32 10, i32 10>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_biggershl_vec_undef1(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggershl_vec_undef1(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 5, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 10, i32 undef, i32 10>
+  ret <3 x i32> %ret
+}
+
+define <3 x i32> @positive_biggershl_vec_undef2(<3 x i32> %x) {
+; CHECK-LABEL: @positive_biggershl_vec_undef2(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <3 x i32> [[TMP0]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = lshr <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = shl <3 x i32> %tmp0, <i32 10, i32 undef, i32 10>
+  ret <3 x i32> %ret
+}
+
+; ============================================================================ ;
+; Constant Non-Splat Vectors
+; ============================================================================ ;
+
+define <2 x i32> @positive_biggerlshr_vec_nonsplat(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggerlshr_vec_nonsplat(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <2 x i32> [[X:%.*]], <i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = shl <2 x i32> [[TMP0]], <i32 5, i32 10>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = lshr <2 x i32> %x, <i32 5, i32 5>
+  %ret = shl <2 x i32> %tmp0, <i32 5, i32 10>
+  ret <2 x i32> %ret
+}
+
+define <2 x i32> @positive_biggerLlshr_vec_nonsplat(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggerLlshr_vec_nonsplat(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr <2 x i32> [[X:%.*]], <i32 5, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = shl <2 x i32> [[TMP0]], <i32 5, i32 5>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = lshr <2 x i32> %x, <i32 5, i32 10>
+  %ret = shl <2 x i32> %tmp0, <i32 5, i32 5>
+  ret <2 x i32> %ret
+}
+
+; ============================================================================ ;
+; Negative tests. Should not be folded.
+; ============================================================================ ;
+
+define i32 @negative_twovars(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @negative_twovars(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = shl i32 [[TMP0]], [[Z:%.*]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr i32 %x, %y
+  %ret = shl i32 %tmp0, %z ; $z, not %y
+  ret i32 %ret
+}
+
+declare void @use32(i32)
+
+; One use only.
+define i32 @negative_oneuse(i32 %x, i32 %y) {
+; CHECK-LABEL: @negative_oneuse(
+; CHECK-NEXT:    [[TMP0:%.*]] = lshr i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[TMP0]])
+; CHECK-NEXT:    [[RET:%.*]] = shl i32 [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = lshr i32 %x, %y
+  call void @use32(i32 %tmp0)
+  %ret = shl i32 %tmp0, %y
+  ret i32 %ret
+}