From 1882c25f124647ba5b5d798dc00c4cd9308536bf Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Thu, 2 Jun 2022 14:02:11 -0400
Subject: [PATCH] [InstCombine] add tests for mul with low-bit mask operand;
 NFC

---
 llvm/test/Transforms/InstCombine/mul.ll | 52 +++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/llvm/test/Transforms/InstCombine/mul.ll b/llvm/test/Transforms/InstCombine/mul.ll
index 895ce433630c..e641e100345f 100644
--- a/llvm/test/Transforms/InstCombine/mul.ll
+++ b/llvm/test/Transforms/InstCombine/mul.ll
@@ -462,6 +462,58 @@ define <2 x i32> @signbit_mul_vec_commute(<2 x i32> %a, <2 x i32> %b) {
   ret <2 x i32> %e
 }
 
+; (A & 1) * B --> (lowbit A) ? B : 0
+
+define i32 @lowbit_mul(i32 %a, i32 %b) {
+; CHECK-LABEL: @lowbit_mul(
+; CHECK-NEXT:    [[D:%.*]] = and i32 [[A:%.*]], 1
+; CHECK-NEXT:    [[E:%.*]] = mul nuw i32 [[D]], [[B:%.*]]
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %d = and i32 %a, 1
+  %e = mul i32 %d, %b
+  ret i32 %e
+}
+
+; (A & 1) * B --> (lowbit A) ? B : 0
+
+define <2 x i17> @lowbit_mul_commute(<2 x i17> %a, <2 x i17> %p) {
+; CHECK-LABEL: @lowbit_mul_commute(
+; CHECK-NEXT:    [[B:%.*]] = xor <2 x i17> [[P:%.*]], <i17 42, i17 43>
+; CHECK-NEXT:    [[D:%.*]] = and <2 x i17> [[A:%.*]], <i17 1, i17 1>
+; CHECK-NEXT:    [[E:%.*]] = mul nuw <2 x i17> [[B]], [[D]]
+; CHECK-NEXT:    ret <2 x i17> [[E]]
+;
+  %b = xor <2 x i17> %p, <i17 42, i17 43> ; thwart complexity-based canonicalization
+  %d = and <2 x i17> %a, <i17 1, i17 1>
+  %e = mul <2 x i17> %b, %d
+  ret <2 x i17> %e
+}
+
+define i32 @lowbit_mul_use(i32 %a, i32 %b) {
+; CHECK-LABEL: @lowbit_mul_use(
+; CHECK-NEXT:    [[D:%.*]] = and i32 [[A:%.*]], 1
+; CHECK-NEXT:    call void @use32(i32 [[D]])
+; CHECK-NEXT:    [[E:%.*]] = mul nuw i32 [[D]], [[B:%.*]]
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %d = and i32 %a, 1
+  call void @use32(i32 %d)
+  %e = mul i32 %d, %b
+  ret i32 %e
+}
+
+define i32 @not_lowbit_mul(i32 %a, i32 %b) {
+; CHECK-LABEL: @not_lowbit_mul(
+; CHECK-NEXT:    [[D:%.*]] = and i32 [[A:%.*]], 2
+; CHECK-NEXT:    [[E:%.*]] = mul i32 [[D]], [[B:%.*]]
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %d = and i32 %a, 2
+  %e = mul i32 %d, %b
+  ret i32 %e
+}
+
 define i32 @signsplat_mul(i32 %x) {
 ; CHECK-LABEL: @signsplat_mul(
 ; CHECK-NEXT:    [[ISNEG:%.*]] = icmp slt i32 [[X:%.*]], 0