[AArch64] Improve code generation for logical instructions taking

immediate operands.

This commit adds an AArch64 dag-combine that optimizes code generation
for logical instructions taking immediate operands. The optimization
uses demanded bits to change a logical instruction's immediate operand
so that the immediate can be folded into the immediate field of the
instruction.

rdar://problem/18231627

Differential Revision: https://reviews.llvm.org/D5591

llvm-svn: 300913

1 files changed, 64 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/optimize-imm.ll b/llvm/test/CodeGen/AArch64/optimize-imm.ll
new file mode 100644
index 00000000000..a4725c65aa2
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/optimize-imm.ll
@@ -0,0 +1,64 @@
+; RUN: llc -o - %s -mtriple=aarch64-- | FileCheck %s
+
+; CHECK-LABEL: and1:
+; CHECK: and {{w[0-9]+}}, w0, #0xfffffffd
+
+define void @and1(i32 %a, i8* nocapture %p) {
+entry:
+  %and = and i32 %a, 253
+  %conv = trunc i32 %and to i8
+  store i8 %conv, i8* %p, align 1
+  ret void
+}
+
+; (a & 0x3dfd) | 0xffffc000
+;
+; CHECK-LABEL: and2:
+; CHECK: and {{w[0-9]+}}, w0, #0xfdfdfdfd
+
+define i32 @and2(i32 %a) {
+entry:
+  %and = and i32 %a, 15869
+  %or = or i32 %and, -16384
+  ret i32 %or
+}
+
+; (a & 0x19) | 0xffffffc0
+;
+; CHECK-LABEL: and3:
+; CHECK: and {{w[0-9]+}}, w0, #0x99999999
+
+define i32 @and3(i32 %a) {
+entry:
+  %and = and i32 %a, 25
+  %or = or i32 %and, -64
+  ret i32 %or
+}
+
+; (a & 0xc5600) | 0xfff1f1ff
+;
+; CHECK-LABEL: and4:
+; CHECK: and {{w[0-9]+}}, w0, #0xfffc07ff
+
+define i32 @and4(i32 %a) {
+entry:
+  %and = and i32 %a, 787968
+  %or = or i32 %and, -921089
+  ret i32 %or
+}
+
+; Make sure we don't shrink or optimize an XOR's immediate operand if the
+; immediate is -1. Instruction selection turns (and ((xor $mask, -1), $v0)) into
+; a BIC.
+
+; CHECK-LABEL: xor1:
+; CHECK: orr [[R0:w[0-9]+]], wzr, #0x38
+; CHECK: bic {{w[0-9]+}}, [[R0]], w0, lsl #3
+
+define i32 @xor1(i32 %a) {
+entry:
+  %shl = shl i32 %a, 3
+  %xor = and i32 %shl, 56
+  %and = xor i32 %xor, 56
+  ret i32 %and
+}