[llvm] r335633 - [InstSimplify] fold shifts by sext bool

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Tue Jun 26 10:31:38 2018
New Revision: 335633

URL: http://llvm.org/viewvc/llvm-project?rev=335633&view=rev
Log:
[InstSimplify] fold shifts by sext bool

https://rise4fun.com/Alive/c3Y

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/shift.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=335633&r1=335632&r2=335633&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Tue Jun 26 10:31:38 2018
@@ -1162,7 +1162,11 @@ static Value *SimplifyShift(Instruction:
     return Constant::getNullValue(Op0->getType());
 
   // X shift by 0 -> X
-  if (match(Op1, m_Zero()))
+  // Shift-by-sign-extended bool must be shift-by-0 because shift-by-all-ones
+  // would be poison.
+  Value *X;
+  if (match(Op1, m_Zero()) ||
+      (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)))
     return Op0;
 
   // Fold undefined shifts.

Modified: llvm/trunk/test/Transforms/InstSimplify/shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/shift.ll?rev=335633&r1=335632&r2=335633&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/shift.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/shift.ll Tue Jun 26 10:31:38 2018
@@ -123,9 +123,7 @@ define <3 x i8> @ashr_all_ones_vec_with_
 
 define i8 @lshr_by_sext_bool(i1 %x, i8 %y) {
 ; CHECK-LABEL: @lshr_by_sext_bool(
-; CHECK-NEXT:    [[S:%.*]] = sext i1 [[X:%.*]] to i8
-; CHECK-NEXT:    [[R:%.*]] = lshr i8 [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 [[Y:%.*]]
 ;
   %s = sext i1 %x to i8
   %r = lshr i8 %y, %s
@@ -134,9 +132,7 @@ define i8 @lshr_by_sext_bool(i1 %x, i8 %
 
 define <2 x i8> @lshr_by_sext_bool_vec(<2 x i1> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @lshr_by_sext_bool_vec(
-; CHECK-NEXT:    [[S:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i8>
-; CHECK-NEXT:    [[R:%.*]] = lshr <2 x i8> [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret <2 x i8> [[R]]
+; CHECK-NEXT:    ret <2 x i8> [[Y:%.*]]
 ;
   %s = sext <2 x i1> %x to <2 x i8>
   %r = lshr <2 x i8> %y, %s
@@ -145,9 +141,7 @@ define <2 x i8> @lshr_by_sext_bool_vec(<
 
 define i8 @ashr_by_sext_bool(i1 %x, i8 %y) {
 ; CHECK-LABEL: @ashr_by_sext_bool(
-; CHECK-NEXT:    [[S:%.*]] = sext i1 [[X:%.*]] to i8
-; CHECK-NEXT:    [[R:%.*]] = ashr i8 [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 [[Y:%.*]]
 ;
   %s = sext i1 %x to i8
   %r = ashr i8 %y, %s
@@ -156,9 +150,7 @@ define i8 @ashr_by_sext_bool(i1 %x, i8 %
 
 define <2 x i8> @ashr_by_sext_bool_vec(<2 x i1> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @ashr_by_sext_bool_vec(
-; CHECK-NEXT:    [[S:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i8>
-; CHECK-NEXT:    [[R:%.*]] = ashr <2 x i8> [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret <2 x i8> [[R]]
+; CHECK-NEXT:    ret <2 x i8> [[Y:%.*]]
 ;
   %s = sext <2 x i1> %x to <2 x i8>
   %r = ashr <2 x i8> %y, %s
@@ -167,9 +159,7 @@ define <2 x i8> @ashr_by_sext_bool_vec(<
 
 define i8 @shl_by_sext_bool(i1 %x, i8 %y) {
 ; CHECK-LABEL: @shl_by_sext_bool(
-; CHECK-NEXT:    [[S:%.*]] = sext i1 [[X:%.*]] to i8
-; CHECK-NEXT:    [[R:%.*]] = shl i8 [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 [[Y:%.*]]
 ;
   %s = sext i1 %x to i8
   %r = shl i8 %y, %s
@@ -178,9 +168,7 @@ define i8 @shl_by_sext_bool(i1 %x, i8 %y
 
 define <2 x i8> @shl_by_sext_bool_vec(<2 x i1> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @shl_by_sext_bool_vec(
-; CHECK-NEXT:    [[S:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i8>
-; CHECK-NEXT:    [[R:%.*]] = shl <2 x i8> [[Y:%.*]], [[S]]
-; CHECK-NEXT:    ret <2 x i8> [[R]]
+; CHECK-NEXT:    ret <2 x i8> [[Y:%.*]]
 ;
   %s = sext <2 x i1> %x to <2 x i8>
   %r = shl <2 x i8> %y, %s