From a24f1373602b68b8dd44a7404fd2e68198bc56e5 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Thu, 20 Apr 2017 21:33:02 +0000
Subject: [PATCH] [InstCombine] allow shl demanded bits folds with splat
 constants

More fixes are needed to enable the helper SimplifyShrShlDemandedBits().



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300898 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 6 ++++--
 test/Transforms/InstCombine/apint-shift.ll                 | 7 ++-----
 test/Transforms/InstCombine/pr17827.ll                     | 4 +---
 test/Transforms/InstCombine/shift.ll                       | 6 ++----
 4 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 230a1ff33d0..3d14e59ea0d 100644
--- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -469,8 +469,9 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
     computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI);
     break;
   }
-  case Instruction::Shl:
-    if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
+  case Instruction::Shl: {
+    const APInt *SA;
+    if (match(I->getOperand(1), m_APInt(SA))) {
       {
         Value *VarX; ConstantInt *C1;
         if (match(I->getOperand(0), m_Shr(m_Value(VarX), m_ConstantInt(C1)))) {
@@ -503,6 +504,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
         KnownZero.setLowBits(ShiftAmt);
     }
     break;
+  }
   case Instruction::LShr: {
     const APInt *SA;
     if (match(I->getOperand(1), m_APInt(SA))) {
diff --git a/test/Transforms/InstCombine/apint-shift.ll b/test/Transforms/InstCombine/apint-shift.ll
index f339de35d77..679a87a7efb 100644
--- a/test/Transforms/InstCombine/apint-shift.ll
+++ b/test/Transforms/InstCombine/apint-shift.ll
@@ -287,13 +287,10 @@ define i47 @test12(i47 %X) {
   ret i47 %sh2
 }
 
-; FIXME: Same as above with vectors.
-
 define <2 x i47> @test12_splat_vec(<2 x i47> %X) {
 ; CHECK-LABEL: @test12_splat_vec(
-; CHECK-NEXT:    [[SH1:%.*]] = ashr <2 x i47> %X, <i47 8, i47 8>
-; CHECK-NEXT:    [[SH2:%.*]] = shl nsw <2 x i47> [[SH1]], <i47 8, i47 8>
-; CHECK-NEXT:    ret <2 x i47> [[SH2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i47> %X, <i47 -256, i47 -256>
+; CHECK-NEXT:    ret <2 x i47> [[TMP1]]
 ;
   %sh1 = ashr <2 x i47> %X, <i47 8, i47 8>
   %sh2 = shl <2 x i47> %sh1, <i47 8, i47 8>
diff --git a/test/Transforms/InstCombine/pr17827.ll b/test/Transforms/InstCombine/pr17827.ll
index ada6edab69c..c9cbf764d7f 100644
--- a/test/Transforms/InstCombine/pr17827.ll
+++ b/test/Transforms/InstCombine/pr17827.ll
@@ -52,9 +52,7 @@ define i1 @test_shift_and_cmp_changed1(i8 %p, i8 %q) {
 define <2 x i1> @test_shift_and_cmp_changed1_vec(<2 x i8> %p, <2 x i8> %q) {
 ; CHECK-LABEL: @test_shift_and_cmp_changed1_vec(
 ; CHECK-NEXT:    [[ANDP:%.*]] = and <2 x i8> %p, <i8 6, i8 6>
-; CHECK-NEXT:    [[ANDQ:%.*]] = and <2 x i8> %q, <i8 8, i8 8>
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i8> [[ANDQ]], [[ANDP]]
-; CHECK-NEXT:    [[SHL:%.*]] = shl <2 x i8> [[OR]], <i8 5, i8 5>
+; CHECK-NEXT:    [[SHL:%.*]] = shl nuw <2 x i8> [[ANDP]], <i8 5, i8 5>
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt <2 x i8> [[SHL]], <i8 32, i8 32>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll
index d5f489280a0..abcb8f17525 100644
--- a/test/Transforms/InstCombine/shift.ll
+++ b/test/Transforms/InstCombine/shift.ll
@@ -1049,12 +1049,11 @@ define i8 @test53_no_nuw(i8 %x) {
 }
 
 ; (X << C1) >>u C2  --> X << (C1 - C2) & (-1 >> C2)
-; FIXME: Demanded bits should change the mask constant as it does for the scalar case.
 
 define <2 x i8> @test53_no_nuw_splat_vec(<2 x i8> %x) {
 ; CHECK-LABEL: @test53_no_nuw_splat_vec(
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <2 x i8> %x, <i8 2, i8 2>
-; CHECK-NEXT:    [[B:%.*]] = and <2 x i8> [[TMP1]], <i8 127, i8 127>
+; CHECK-NEXT:    [[B:%.*]] = and <2 x i8> [[TMP1]], <i8 124, i8 124>
 ; CHECK-NEXT:    ret <2 x i8> [[B]]
 ;
   %A = shl <2 x i8> %x, <i8 3, i8 3>
@@ -1257,8 +1256,7 @@ define i64 @test_64(i32 %t) {
 
 define <2 x i64> @test_64_splat_vec(<2 x i32> %t) {
 ; CHECK-LABEL: @test_64_splat_vec(
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i32> %t, <i32 16777215, i32 16777215>
-; CHECK-NEXT:    [[TMP1:%.*]] = shl nuw <2 x i32> [[AND]], <i32 8, i32 8>
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <2 x i32> %t, <i32 8, i32 8>
 ; CHECK-NEXT:    [[SHL:%.*]] = zext <2 x i32> [[TMP1]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[SHL]]
 ;
-- 
2.50.1