[ARM] Prefer lsls+lsrs over lsls+ands or lsrs+ands in Thumb1.

Saves materializing the immediate for the "ands".

Corresponding patterns exist for lsrs+lsls, but that seems less common
in practice.

Now implemented as a DAGCombine.

Differential Revision: https://reviews.llvm.org/D49585

llvm-svn: 337945

1 files changed, 125 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Thumb/shift-and.ll b/llvm/test/CodeGen/Thumb/shift-and.ll
new file mode 100644
index 00000000000..fa6ee1db5e2
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb/shift-and.ll
@@ -0,0 +1,125 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=thumbv6-eabi %s -o - | FileCheck %s
+
+define i32 @test1(i32 %x) {
+; CHECK-LABEL: test1:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsls r0, r0, #20
+; CHECK-NEXT:    lsrs r0, r0, #22
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = lshr i32 %x, 2
+  %shr = and i32 %0, 1023
+  ret i32 %shr
+}
+
+define i32 @test2(i32 %x) {
+; CHECK-LABEL: test2:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsrs r1, r0, #2
+; CHECK-NEXT:    ldr r0, .LCPI1_0
+; CHECK-NEXT:    ands r0, r1
+; CHECK-NEXT:    bx lr
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  @ %bb.1:
+; CHECK-NEXT:  .LCPI1_0:
+; CHECK-NEXT:    .long 1022 @ 0x3fe
+entry:
+  %0 = lshr i32 %x, 2
+  %shr = and i32 %0, 1022
+  ret i32 %shr
+}
+
+define i32 @test3(i32 %x) {
+; CHECK-LABEL: test3:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsrs r0, r0, #2
+; CHECK-NEXT:    uxtb r0, r0
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = lshr i32 %x, 2
+  %shr = and i32 %0, 255
+  ret i32 %shr
+}
+
+define i32 @test4(i32 %x) {
+; CHECK-LABEL: test4:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsls r0, r0, #4
+; CHECK-NEXT:    movs r1, #127
+; CHECK-NEXT:    bics r0, r1
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = shl i32 %x, 4
+  %shr = and i32 %0, -128
+  ret i32 %shr
+}
+
+define i32 @test5(i32 %x) {
+; CHECK-LABEL: test5:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsls r0, r0, #31
+; CHECK-NEXT:    lsrs r0, r0, #2
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = shl i32 %x, 29
+  %shr = and i32 %0, 536870912
+  ret i32 %shr
+}
+
+define i32 @test6(i32 %x) {
+; CHECK-LABEL: test6:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    movs r1, #5
+; CHECK-NEXT:    lsls r1, r1, #29
+; CHECK-NEXT:    lsls r0, r0, #29
+; CHECK-NEXT:    ands r0, r1
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = shl i32 %x, 29
+  %shr = and i32 %0, 2684354560
+  ret i32 %shr
+}
+
+define i32 @test7(i32 %x) {
+; CHECK-LABEL: test7:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsrs r1, r0, #29
+; CHECK-NEXT:    movs r0, #4
+; CHECK-NEXT:    ands r0, r1
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = lshr i32 %x, 29
+  %shr = and i32 %0, 4
+  ret i32 %shr
+}
+
+define i32 @test8(i32 %x) {
+; CHECK-LABEL: test8:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsrs r1, r0, #29
+; CHECK-NEXT:    movs r0, #5
+; CHECK-NEXT:    ands r0, r1
+; CHECK-NEXT:    bx lr
+entry:
+  %0 = lshr i32 %x, 29
+  %shr = and i32 %0, 5
+  ret i32 %shr
+}
+
+define i32 @test9(i32 %x) {
+; CHECK-LABEL: test9:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    lsrs r1, r0, #2
+; CHECK-NEXT:    ldr r0, .LCPI8_0
+; CHECK-NEXT:    ands r0, r1
+; CHECK-NEXT:    bx lr
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  @ %bb.1:
+; CHECK-NEXT:  .LCPI8_0:
+; CHECK-NEXT:    .long 1073741822 @ 0x3ffffffe
+entry:
+  %and = lshr i32 %x, 2
+  %shr = and i32 %and, 1073741822
+  ret i32 %shr
+}