From 794e29f964c41504e2a06c9f09984a7278b16c91 Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Sat, 9 Jun 2018 09:27:39 +0000
Subject: [PATCH] [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://rise4fun.com/Alive/cplX

llvm-svn: 334346
---
 .../canonicalize-shl-lshr-to-masking.ll       | 315 ++++++++++++++++++
 1 file changed, 315 insertions(+)
 create mode 100644 llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll

diff --git a/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll b/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll
new file mode 100644
index 000000000000..10a9a10dfda6
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll
@@ -0,0 +1,315 @@
+; 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
+
+; 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:%.*]] = shl i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = lshr i32 [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl i32 %x, %y
+  %ret = lshr i32 %tmp0, %y
+  ret i32 %ret
+}
+
+define i32 @positive_sameconst(i32 %x) {
+; CHECK-LABEL: @positive_sameconst(
+; CHECK-NEXT:    [[TMP0:%.*]] = and i32 [[X:%.*]], 134217727
+; CHECK-NEXT:    ret i32 [[TMP0]]
+;
+  %tmp0 = shl i32 %x, 5
+  %ret = lshr i32 %tmp0, 5
+  ret i32 %ret
+}
+
+define i32 @positive_biggerShl(i32 %x) {
+; CHECK-LABEL: @positive_biggerShl(
+; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 [[X:%.*]], 5
+; CHECK-NEXT:    [[RET:%.*]] = and i32 [[TMP1]], 134217696
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl i32 %x, 10
+  %ret = lshr i32 %tmp0, 5
+  ret i32 %ret
+}
+
+define i32 @positive_biggerLshr(i32 %x) {
+; CHECK-LABEL: @positive_biggerLshr(
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[X:%.*]], 5
+; CHECK-NEXT:    [[RET:%.*]] = and i32 [[TMP1]], 4194303
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl i32 %x, 5
+  %ret = lshr i32 %tmp0, 10
+  ret i32 %ret
+}
+
+; ============================================================================ ;
+; NUW on the first shift
+; ============================================================================ ;
+
+define i32 @positive_samevar_shlnuw(i32 %x, i32 %y) {
+; CHECK-LABEL: @positive_samevar_shlnuw(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %tmp0 = shl nuw i32 %x, %y
+  %ret = lshr i32 %tmp0, %y ; this one is obviously 'exact'.
+  ret i32 %ret
+}
+
+define i32 @positive_sameconst_shlnuw(i32 %x) {
+; CHECK-LABEL: @positive_sameconst_shlnuw(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %tmp0 = shl nuw i32 %x, 5
+  %ret = lshr i32 %tmp0, 5 ; this one is obviously 'exact'.
+  ret i32 %ret
+}
+
+define i32 @positive_biggerShl_shlnuw(i32 %x) {
+; CHECK-LABEL: @positive_biggerShl_shlnuw(
+; CHECK-NEXT:    [[RET:%.*]] = shl nuw i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl nuw i32 %x, 10
+  %ret = lshr i32 %tmp0, 5 ; this one is obviously 'exact'.
+  ret i32 %ret
+}
+
+define i32 @positive_biggerLshr_shlnuw(i32 %x) {
+; CHECK-LABEL: @positive_biggerLshr_shlnuw(
+; CHECK-NEXT:    [[RET:%.*]] = lshr i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl nuw i32 %x, 5
+  %ret = lshr i32 %tmp0, 10
+  ret i32 %ret
+}
+
+define i32 @positive_biggerLshr_shlnuw_lshrexact(i32 %x) {
+; CHECK-LABEL: @positive_biggerLshr_shlnuw_lshrexact(
+; CHECK-NEXT:    [[RET:%.*]] = lshr exact i32 [[X:%.*]], 5
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl nuw i32 %x, 5
+  %ret = lshr exact 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:%.*]] = shl <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = lshr <2 x i32> [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = shl <2 x i32> %x, %y
+  %ret = lshr <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 134217727, i32 134217727>
+; CHECK-NEXT:    ret <2 x i32> [[TMP0]]
+;
+  %tmp0 = shl <2 x i32> %x, <i32 5, i32 5>
+  %ret = lshr <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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = lshr <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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 5, i32 5>
+  %ret = lshr <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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = lshr <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:    [[TMP1:%.*]] = shl <2 x i32> [[X:%.*]], <i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = and <2 x i32> [[TMP1]], <i32 134217696, i32 134217696>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = shl <2 x i32> %x, <i32 10, i32 10>
+  %ret = lshr <2 x i32> %tmp0, <i32 5, i32 5>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 10, i32 undef, i32 10>
+  %ret = lshr <3 x i32> %tmp0, <i32 5, i32 5, i32 5>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 10, i32 10, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 10, i32 10, i32 10>
+  %ret = lshr <3 x i32> %tmp0, <i32 5, i32 undef, i32 5>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 10, i32 undef, i32 10>
+  %ret = lshr <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:    [[TMP1:%.*]] = lshr <2 x i32> [[X:%.*]], <i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = and <2 x i32> [[TMP1]], <i32 4194303, i32 4194303>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = shl <2 x i32> %x, <i32 5, i32 5>
+  %ret = lshr <2 x i32> %tmp0, <i32 10, i32 10>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 10, i32 10, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = lshr <3 x i32> %tmp0, <i32 10, i32 10, i32 10>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 5, i32 5>
+  %ret = lshr <3 x i32> %tmp0, <i32 10, i32 undef, i32 10>
+  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:%.*]] = shl <3 x i32> [[X:%.*]], <i32 5, i32 undef, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <3 x i32> [[TMP0]], <i32 10, i32 undef, i32 10>
+; CHECK-NEXT:    ret <3 x i32> [[RET]]
+;
+  %tmp0 = shl <3 x i32> %x, <i32 5, i32 undef, i32 5>
+  %ret = lshr <3 x i32> %tmp0, <i32 10, i32 undef, i32 10>
+  ret <3 x i32> %ret
+}
+
+; ============================================================================ ;
+; Constant Non-Splat Vectors
+; ============================================================================ ;
+
+define <2 x i32> @positive_biggerShl_vec_nonsplat(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggerShl_vec_nonsplat(
+; CHECK-NEXT:    [[TMP0:%.*]] = shl <2 x i32> [[X:%.*]], <i32 5, i32 5>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <2 x i32> [[TMP0]], <i32 5, i32 10>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = shl <2 x i32> %x, <i32 5, i32 5>
+  %ret = lshr <2 x i32> %tmp0, <i32 5, i32 10>
+  ret <2 x i32> %ret
+}
+
+define <2 x i32> @positive_biggerLshl_vec_nonsplat(<2 x i32> %x) {
+; CHECK-LABEL: @positive_biggerLshl_vec_nonsplat(
+; CHECK-NEXT:    [[TMP0:%.*]] = shl <2 x i32> [[X:%.*]], <i32 5, i32 10>
+; CHECK-NEXT:    [[RET:%.*]] = lshr <2 x i32> [[TMP0]], <i32 5, i32 5>
+; CHECK-NEXT:    ret <2 x i32> [[RET]]
+;
+  %tmp0 = shl <2 x i32> %x, <i32 5, i32 10>
+  %ret = lshr <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:%.*]] = shl i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = lshr i32 [[TMP0]], [[Z:%.*]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl i32 %x, %y
+  %ret = lshr 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:%.*]] = shl i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use32(i32 [[TMP0]])
+; CHECK-NEXT:    [[RET:%.*]] = lshr i32 [[TMP0]], [[Y]]
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %tmp0 = shl i32 %x, %y
+  call void @use32(i32 %tmp0)
+  %ret = lshr i32 %tmp0, %y
+  ret i32 %ret
+}