[PATCH] D156881: [InstSimplify] Check the isNonNegative for Power2 value

[Allen zhong via Phabricator via llvm-commits]

Allen created this revision.
Allen added reviewers: nikic, goldstein.w.n, mstorsjo, dmgreen.
Herald added subscribers: StephenFan, hiraditya.
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Allen requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Fixes https://github.com/llvm/llvm-project/issues/64339


https://reviews.llvm.org/D156881

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstCombine/rem-mul-shl.ll


Index: llvm/test/Transforms/InstCombine/rem-mul-shl.ll
===================================================================
--- llvm/test/Transforms/InstCombine/rem-mul-shl.ll
+++ llvm/test/Transforms/InstCombine/rem-mul-shl.ll
@@ -2,6 +2,7 @@
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 declare void @use8(i8)
 declare i64 @llvm.vscale.i64()
+declare i32 @llvm.vscale.i32()
 
 define i8 @srem_non_matching(i8 %X, i8 %Y) {
 ; CHECK-LABEL: @srem_non_matching(
@@ -913,3 +914,20 @@
   %rem = and i64 3072, %add
   ret i64 %rem
 }
+
+; Negative test: -2147483648 is a negative value of i32
+define i32 @and_add_shl_vscale_not_power2_negative() vscale_range(1,16) {
+; CHECK-LABEL: @and_add_shl_vscale_not_power2_negative(
+; CHECK-NEXT:    [[VSCALE:%.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT:    [[SHIFT:%.*]] = shl nuw nsw i32 [[VSCALE]], 6
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SHIFT]], -1
+; CHECK-NEXT:    [[REM:%.*]] = and i32 [[ADD]], -2147483648
+; CHECK-NEXT:    ret i32 [[REM]]
+;
+  %vscale = call i32 @llvm.vscale.i32()
+  %shift = shl nuw nsw i32 %vscale, 6
+  %add = add i32 %shift, -1
+  %rem = and i32 -2147483648, %add
+  ret i32 %rem
+}
+
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2119,7 +2119,7 @@
   // and 2^x-1, 2^C --> 0 where x <= C.
   const APInt *PowerC;
   Value *Shift;
-  if (match(Op1, m_Power2(PowerC)) &&
+  if (match(Op1, m_Power2(PowerC)) && PowerC->isNonNegative() &&
       match(Op0, m_Add(m_Value(Shift), m_AllOnes())) &&
       isKnownToBeAPowerOfTwo(Shift, Q.DL, /*OrZero*/ true, 0, Q.AC, Q.CxtI,
                              Q.DT)) {


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